Evidence Report/Technology Assessment 

Number 191 

Vaginal Birth After Cesarean: New Insights 

Prepared for: 

Agency for Healthcare Research and Quality 

U.S. Department of Health and Human Services 

540 Gaither Road 

Rockville, MD 20850 

www.ahrq.gov 

Contract No. 290-2007-10057-I 

Prepared by 

Oregon Evidence-based Practice Center, Oregon Health & Science University, Portland, Oregon 

Investigator Team 

Jeanne-Marie Guise, M.D., M.P.H. 

Karen Eden, Ph.D. 

Cathy Emeis, Ph.D., C.N.M. 

Mary Anna Denman, M.D. 

Nicole Marshall, M.D. 

Rongwei (Rochelle) Fu, Ph.D. 

Rosalind Janik, B.A. 

Peggy Nygren, M.A. 

Miranda Walker, M.A. 

Marian McDonagh, Pharm.D. 

AHRQ Publication No. 10-E003

March 2010 
This information is based on research conducted by the Oregon Evidence-based Practice Center 

(EPC) under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, 

MD (Contract No. 290-2007-10057-I). The findings and conclusions in this document are those 

of the authors, who are responsible for its content, and do not necessarily represent the views of 

AHRQ. No statement in this report should be construed as an official position of AHRQ or of the 

U.S. Department of Health and Human Services. 

The information in this report is intended to help clinicians, employers, policymakers, and other 

make informed decisions about the provision of health care services. This report is intended as a 

reference and not as a substitute for clinical judgment. 

This report may be used, in whole or in part, as the basis for development of clinical practice 

guidelines and other quality enhancement tools, or a basis for reimbursement and coverage 

policies. AHRQ or U.S. Department of Health and Human Services endorsement of such 

derivative products may not be stated or implied. 
This document is in the public domain and may be used and reprinted without permission except 

those copyrighted materials noted for which further reproduction is prohibited without the 

specific permission of copyright holders. 

Suggested Citation: 

Guise J-M, Eden K, Emeis C, Denman MA, Marshall N, Fu R, Janik R, Nygren P, Walker M, 

McDonagh M. Vaginal Birth After Cesarean: New Insights. Evidence Report/Technology 

Assessment No.191. (Prepared by the Oregon Health & Science University Evidence-based 

Practice Center under Contract No. 290-2007-10057-I). AHRQ Publication No. 10-E003. 

Rockville, MD: Agency for Healthcare Research and Quality. March 2010. 

No investigators have any affiliations or financial involvement (e.g., employment, 

consultancies, honoraria, stock options, expert testimony, grants or patents received or 

pending, or royalties) that conflict with material presented in this report. 

ii 
 

 

Preface 

 The Agency for Healthcare Research and Quality (AHRQ), through its Evidence-Based 

Practice Centers (EPCs), sponsors the development of evidence reports and technology 

assessments to assist public- and private-sector organizations in their efforts to improve the 

quality of health care in the United States. This report was requested by the NIH Office of 

Medical Applications of Research as a background paper for the Consensus Development 

Conference on Vaginal Birth After Cesarean – New Insights. The reports and assessments 

provide organizations with comprehensive, science-based information on common, costly 

medical conditions, and new health care technologies. The EPCs systematically review the 

relevant scientific literature on topics assigned to them by AHRQ and conduct additional 

analyses when appropriate prior to developing their reports and assessments. 

 To bring the broadest range of experts into the development of evidence reports and health 

technology assessments, AHRQ encourages the EPCs to form partnerships and enter into 

collaborations with other medical and research organizations. The EPCs work with these partner 

organizations to ensure that the evidence reports and technology assessments they produce will 

become building blocks for health care quality improvement projects throughout the Nation. The 

reports undergo peer review prior to their release. 

 AHRQ expects that the EPC evidence reports and technology assessments will inform 

individual health plans, providers, and purchasers as well as the health care system as a whole by 

providing important information to help improve health care quality. 

 We welcome written comments on this evidence report. They may be sent to the Task Order 

Officer named below at: Agency for Healthcare Research and Quality, 540 Gaither Road, 

Rockville, MD 20850, or by email to epc@ahrq.gov. 

Carolyn M. Clancy, M.D. Jean Slutsky, P.A., M.S.P.H. 

Director Director, Center for Outcomes and Evidence 

Agency for Healthcare Research and Quality Agency for Healthcare Research and Quality 

Beth A. Collins Sharp, R.N., Ph.D. Shilpa Amin, M.D., M.B.sc, FAAFP 

Director, EPC Program EPC Program Task Order Officer 

Agency for Healthcare Research and Quality Agency for Healthcare Research and Quality 

Jennifer Croswell, M.D., M.P.H. 

Acting Director 

Office of Medical Applications of Research 

National Institutes of Health 

iii 
Acknowledgments 

 This systematic evidence review was developed for the National Institutes of Health 

Consensus Development Conference on Vaginal Birth After Cesarean: New Insights. It was 

supported by the Office of Medical Applications of Research (OMAR) at the National Institutes 

of Health and the Agency for Healthcare Research and Quality (AHRQ) and the investigators 

acknowledge the contributions of Shilpa Amin, M.D., M.B.sc, FAAFP, Task Order Officer, 

AHRQ; Lata Nerurkar, Ph.D., OMAR, Jennifer Croswell, M.D., M.P.H, OMAR; and Gary 

Cunningham, M.D., Chair of the Consensus Development Conference Panel. Investigators thank 

the Technical Expert Panel members for providing guidance for the project, the peer reviewers 

for providing feedback on the draft report, Andrew Hamilton, M.L.S., M.S., for conducting the 

literature searches; and Benjamin Chan, M.S., for providing statistical assistance; Abby Parsons, 

M.D., for providing abstract and paper review assistance; JoDee Anderson, M.D. for assistance 

on neonatal outcomes; and Alia Broman for data abstraction assistance. 

iv 
Structured Abstract 

Objectives: To synthesize the published literature on vaginal birth after cesarean (VBAC). 

Specifically, to review the trends and incidence of VBAC, maternal benefits and harms, infant 

benefits and harms, relevant factors influencing each, and the directions for future research. 

Data Sources: Relevant studies were identified from multiple searches of MEDLINE®; DARE; 

the Cochrane databases (1966 to September 2009); and from recent systematic reviews, 

reference lists, reviews, editorials, Web sites, and experts. 

Review Methods: Specific inclusion and exclusion criteria were developed to determine study 

eligibility. The target population includes healthy women of reproductive age, with a singleton 

gestation, in the U.S. with a prior cesarean who are eligible for a trial of labor (TOL) or elective 

repeat cesarean delivery (ERCD). All eligible studies were quality rated and data were extracted 

from good or fair quality studies, entered into tables, summarized descriptively and, when 

appropriate, pooled for analysis. The primary focus of the report was term pregnancies. 

However, due to a small number of studies on term pregnancies, general population studies 

including all gestational ages (GA) were included in appropriate areas. 

Results: We identified 3,134 citations and reviewed 963 papers for inclusion, of which 203 

papers met inclusion and were quality rated. Studies of maternal and infant outcomes reported 

data based upon actual rather than intended router of delivery. The range for TOL and VBAC 

rates was large (28-82 percent and 49-87 percent, respectively) with the highest rates being 

reported in studies outside of the U.S. Predictors of women having a TOL were having a prior 

vaginal delivery and settings of higher-level care (e.g., tertiary care centers). TOL rates in U.S. 

studies declined in studies initiated after 1996 from 63 to 47 percent, but the VBAC rate 

remained unimproved. Hispanic and African American women were less likely than their white 

counterparts to have a vaginal delivery. Overall rates of maternal harms were low for both TOL 

and ERCD. While rare for both TOL and ERCD, maternal mortality was significantly increased 

for ERCD at 13.4 per 100,000 versus 3.8 per 100,000 for TOL. The rates of maternal 

hysterectomy, hemorrhage, and transfusions did not differ significantly between TOL and 

ERCD. The rate of uterine rupture for all women with prior cesarean is 3 per 1,000 and the 

risk was significantly increased with TOL (4.7/1,000 versus 0.3/1,000 ERCD). Six percent of 

uterine ruptures were associated with perinatal death. No models have been able to accurately 

predict women who are more likely to deliver by VBAC or to rupture. Women with a prior 

cesarean delivery had a statistically significant increased risk of placenta previa compared with 

women with no prior cesarean, at a rate of 12 per 1,000 and risk increasing with the number of 

cesareans. Women with one prior cesarean and previa had a statistically significant increased risk 

of adverse events compared with previa patients without a prior cesarean delivery: blood 

transfusion (15 versus 32.2 percent), hysterectomy (0.7 to 4 percent versus 10 percent), and 

composite maternal morbidity (15 versus 23-30 percent). Perinatal mortality was significantly 

increased for TOL at 1.3 per 1,000 versus 0.5 per 1,000 for ERCD. Insufficient data were found 

on nonmedical factors such as medical liability, economics, hospital staffing, structure and 

setting, which all appear to be important drivers for VBAC. 

v 
Conclusions: Each year 1.5 million childbearing women have cesarean deliveries, and this 

population continues to increase. This report adds stronger evidence that VBAC is a reasonable 

and safe choice for the majority of women with prior cesarean. Moreover, there is emerging 

evidence of serious harms relating to multiple cesareans. Relatively unexamined contextual 

factors such as medical liability, economics, hospital structure, and staffing may need to be 

addressed to prioritize VBAC services. There is still no evidence to inform patients, clinicians, or 

policy-makers about the outcomes of intended route of delivery because the evidence is based 

largely on the actual route of delivery. This inception cohort is the equivalent of intention to treat 

for randomized controlled trials and this gap in information is critical. A list of future research 

considerations as prioritized by national experts is also highlighted in this report. 

vi 
 

 

 

 

 

 

 

 

 

 

 

Contents 

Executive Summary......................................................................................................................1 

Evidence Report..........................................................................................................................9
 

Chapter 1. Introduction ...............................................................................................................11 

What are the rates and patterns of utilization of trial of labor after prior cesarean, 

What are the nonmedical factors (provider type, hospital type, etc) that influence the 

Structure of Report and Key Questions ................................................................................13 

 Background Questions....................................................................................................13 

 Key Questions.................................................................................................................13 

Introduction...........................................................................................................................13 

Background...........................................................................................................................14 

vaginal birth after cesarean, and repeat cesarean delivery in the United States? ...........14 

patterns of utilization of trial of labor after prior cesarean? ........................................17 

Chapter 2. Methods.....................................................................................................................21 

 Topic Development...............................................................................................................21 

Analytic Framework and Key Questions........................................................................21 

 Technical Expert Panel and Expert Reviewers...............................................................23 

Literature Search and Strategy..............................................................................................23
 

Inclusion and Exclusion Criteria...........................................................................................23 

General............................................................................................................................24 

 Key Question 1 ...............................................................................................................24 

 Key Question 2 ...............................................................................................................25 

 Key Question 3 ...............................................................................................................25 

 Key Question 4 ...............................................................................................................26 

 Special Considerations....................................................................................................26 

Data Extraction and Synthesis ..............................................................................................27 

Quality Rating of Individual Studies ..............................................................................27 

Development of Evidence Tables and Data Abstraction Process...................................27 

 Strength of Available Evidence ......................................................................................28 

 Data Synthesis.................................................................................................................29 

Size of Literature...................................................................................................................30 

Chapter 3. Results .......................................................................................................................33 

Among women who attempt a trial of labor after prior cesarean, what is the vaginal delivery 

rate and the factors that influence it? .................................................................................33 

Trial of Labor Rate..........................................................................................................33 

Predictors of Trial of Labor ............................................................................................36 

Vaginal Birth After Cesarean Rate .................................................................................36 

 Induction of Labor ..........................................................................................................36 

Predictors of Vaginal Birth After Cesarean....................................................................44 

Screening Tools for Predicting Vaginal Birth After Cesarean .......................................46 

vii 
 

 

 

 

 

 

What are the short- and long-term benefits and harms to the mother of attempting trial of 

labor after prior cesarean versus elective repeat cesarean delivery, and what factors 

influence benefits and harms?............................................................................................47 

 Maternal Death................................................................................................................47 

 Uterine Rupture...............................................................................................................51 

Hysterectomy ..................................................................................................................73 

 Transfusions/Hemorrhage...............................................................................................77 

Infection ..........................................................................................................................84 

 Surgical Injury ................................................................................................................84 

 Hospital Stay...................................................................................................................88 

 Pelvic Floor.....................................................................................................................89 

 Deep Vein Thrombosis ...................................................................................................89 

 Special Considerations....................................................................................................90 

Adhesions......................................................................................................................116 

 Reproductive Health .....................................................................................................116 

What are the short- and long-term benefits and harms to the baby of maternal attempt at trial 

of labor after prior cesarean versus elective repeat cesarean delivery, and what factors 

influence benefits and harms?..........................................................................................117 

 Perinatal Mortality ........................................................................................................117 

 Infant Morbidity............................................................................................................127 

Sepsis ............................................................................................................................132 

 Birth Trauma.................................................................................................................132 

 Apgar Scores.................................................................................................................133 

 Neonatal Intensive Care Unit Admissions....................................................................133 

Breastfeeding ................................................................................................................138 

Impact of Mode of Delivery on Subsequent Babies .....................................................138 

 Neurological Development ...........................................................................................139 

 Special Considerations..................................................................................................139 

Chapter 4. Discussion ...............................................................................................................143 

What are the critical gaps in the evidence for decision-making, and what are the priority 

investigations needed to address these gaps?...................................................................151 

National Childbirth Study................................................................................................151 

Prediction Tools...............................................................................................................152 

Maternal Health Outcomes ..............................................................................................152 

Infant Health Outcomes ...................................................................................................153 

Cost ..................................................................................................................................153 

References and Included Studies ..............................................................................................157 

Acronyms/Abbreviations ..........................................................................................................169 

viii 
Tables 

Table 1 Reasons behind women’s decisions for repeat cesarean delivery ...............................17 

Table 2 Vaginal birth after cesarean rates by types of induction..............................................37 

Table 3 Vaginal birth after cesarean and proportion with augmented labor in women 

induced with prostaglandin E2 .....................................................................................39 

Table 4 Vaginal birth after cesarean rate with oxytocin used for induction versus 

augmentation................................................................................................................42 

Table 5 Most commonly reported indications and pooled proportions ....................................43 

Table 6 Uterine rupture: trial of labor versus elective repeat cesarean delivery among any 

gestational age studies..................................................................................................51 

Table 7 Characteristics of uterine rupture studies of trial of labor and elective repeat 

 cesarean delivery..........................................................................................................54 

Table 8 Rupture associated morbidity ......................................................................................56 

Table 9 Effect of oxytocin augmentation on rate of uterine rupture in women receiving 

prostaglandin E2 for induction .....................................................................................65 

Table 10 The odds of uterine rupture after cesarean delivery by factor .....................................68 

Table 11 Lower uterine segment thickness and uterine defect ...................................................71 

Table 12 Hysterectomy rates of trial of labor versus elective repeat cesarean delivery.............75 

Table 13 Surgical injury rates for trial of labor versus elective repeat cesarean delivery among 

any gestational studies .................................................................................................86 

Table 14 Abruption based on number of prior cesarean deliveries ............................................91 

Table 15 Blood transfusion by number of prior cesarean deliveries ..........................................92 

Table 16 Overall incidence of placenta previa............................................................................92 

Table 17 Incidence of placenta previa by number of prior cesarean deliveries..........................93 

Table 18 Incidence of hysterectomy in women with previa by number of prior cesarean 

deliveries......................................................................................................................97 

Table 19 Overall incidence of placenta accreta ..........................................................................97 

Table 20 Incidence of placenta accreta by number of prior cesarean deliveries ........................98 

Table 21 Incidence of placenta accreta with placenta previa by number of prior cesarean 

deliveries......................................................................................................................99 

Table 22 Multiple cesarean deliveries effect on rates of hemorrhage ......................................101 

Table 23 Multiple cesarean deliveries effect on rates of adhesions..........................................102 

Table 24 Multiple cesarean deliveries effect on rates of surgical injury ..................................103 

Table 25 Multiple cesarean deliveries effect on rates of perioperative infection .....................103 

Table 26 Multiple cesarean deliveries effect on rates of wound complications .......................104 

Table 27 Multiple cesarean deliveries effect on rates of hysterectomy....................................105 

Table 28 Impact of direction of scar .........................................................................................107 

Table 29 Vaginal birth after cesarean rate in studies with data by body mass index ...............111 

Table 30 Summary of findings on maternal and infant health outcomes for trial of labor and 

body mass index.........................................................................................................114 

Table 31 Perinatal mortality rate (20 weeks or greater gestation to 7 days of life) among any 

gestational age studies ...............................................................................................119 

Table 32 Fetal mortality rate (20 weeks or greater gestation and before birth) among term
 

studies ........................................................................................................................122 

Table 33 Neonatal mortality rate (death occurring in the first 28 days of life) among term
 

studies ........................................................................................................................124 

ix 
Table 34 Comparison of cohort studies reporting respiratory morbidity in infants among 

 term studies ................................................................................................................128 

Table 35 Neonatal intensive care unit admissions among term studies....................................136 

Table 36 Summary of evidence for key questions....................................................................146 

Table 37 Future research...........................................................................................................154 

Figures 

Figure 1 Rates of vaginal birth after cesarean (VBAC rate), total cesarean deliveries (CD rate), 

primary cesarean deliveries (Primary CD), and repeat cesarean delivery (RCD) .........................12 

Figure 11 Uterine rupture among studies including both trial of labor and elective repeat 

Figure 21 Transfusion rates for trial of labor versus elective repeat cesarean among all studies78 

Figure 22 Transfusion rates for trial of labor versus elective repeat cesarean delivery among 

Figure 23 Rates of infection for trial of labor versus elective repeat cesarean delivery among all 

Figure 24 Rates of fever for trial of labor versus elective repeat cesarean delivery among all 

Figure 25 Length of stay for trial of labor versus elective repeat cesarean delivery among any 

Figure 26 Incidence of placenta previa by number of prior cesarean deliveries among any 

Figure 27 Perinatal mortality rate for trial of labor versus elective repeat cesarean delivery 

Figure 28 Neonatal mortality rate for trial of labor versus elective repeat cesarean delivery 

Figure 2 Cesarean delivery by country - percent for live births (2007).....................................15 

Figure 3 Vaginal birth after cesarean rates by state for 2006.....................................................16 

Figure 4 Analytic Framework ....................................................................................................22 

Figure 5 Search and Selection of Literature...............................................................................31 

Figure 6 Trial of labor in studies conducted in the U.S. and outside the U.S ............................34 

Figure 7 Global trial of labor rates have dropped over time ......................................................35 

Figure 8 Vaginal birth after cesarean rates with oxytocin induction .........................................41 

Figure 9 Rates of maternal death for trial of labor among all studies........................................49 

Figure 10 Rates of maternal death for elective repeat cesarean delivery among all studies........50 

cesarean delivery............................................................................................................................53 

Figure 12 Uterine rupture among all trial of labor studies...........................................................55 

Figure 13 Risk for perinatal death given uterine rupture .............................................................57 

Figure 14 Uterine rupture with induction of a trial of labor.........................................................59 

Figure 15 Risk of rupture: induction versus spontaneous labor...................................................60 

Figure 16 Uterine rupture with prostaglandin E2 induction .........................................................62 

Figure 17 Uterine rupture with oxytocin......................................................................................64
 

Figure 18 Risk of uterine rupture with any induction method .....................................................67 

Figure 19 Hysterectomy occurrence for trial of labor..................................................................76 

Figure 20 Hysterectomy occurrence for elective repeat cesarean delivery..................................77 

term studies ....................................................................................................................................79 

studies ......................................................................................................................................82 

studies ......................................................................................................................................84 

gestational age studies....................................................................................................................89 

gestational age studies....................................................................................................................96 

among any gestational age studies...............................................................................................120 

among term studies ......................................................................................................................128 

Figure 29 Need for bag-and-mask resuscitation among term studies ........................................129 

x 
Figure 30 Rates of transient tachypnea of the newborn for trial of labor versus elective repeat 

cesarean delivery among term studies .........................................................................................130 

Appendixes 

Appendix A Technical Expert Members 

Appendix B Expert Reviewers 

Appendix C Search Strategies 

Appendix D List of Developed Countries 

Appendix E Inclusion and Exclusion Criteria 

Appendix F Excluded Studies List 

Appendix G List of Citations From the Maternal-Fetal Medicine Units Network 

Appendix H Quality Rating Criteria 

Appendix I Individual Quality Rating Tables 

Appendix J Strength of Evidence Table 

Appendix K Detailed Evaluation of Predictors of Trial of Labor and Vaginal Birth After 

Cesarean 

Appendix L Detailed Evaluation of Vaginal Birth After Cesarean Rates 

Appendix M Induction of Labor Additional Figures 

Appendix N Detailed Evaluation of Screening Tools for Predicting Vaginal Birth After 

Cesarean 

Appendix O Detailed Maternal Mortality Table 

Appendix P Predictive Tools of Uterine Rupture Table 

Appendix Q Detailed Transfuion/Hemorrhage Table 

Appendix R Detailed Infection Table 

Appendix S Detailed Hopsital Stay Table 

Appendixes and evidence tables cited in this report are available at 

http://www.ahrq.gov/downloads/pub/evidence/pdf/vbacup/vbacup.pdf. 

xi 
 

Executive Summary 

Introduction 

Despite the Healthy People 2010 national goal1 to reduce the cesarean delivery rate to 15 

percent of births each year, this century has set record rates of cesarean deliveries. When the 

national rate of cesarean delivery was first measured in 1965, it was 4.5 percent,2 in 2007, almost 

one in three women in the United States (U.S.) delivered by cesarean (32.8 percent cesarean 

delivery rate in 2007). With almost 1.5 million cesarean surgeries performed every year, 

cesarean is the most common surgical procedure in the U.S. Vaginal birth after cesarean (VBAC) 

emerged from the 1980 National Institutes of Health (NIH) Consensus Conference on Cesarean 

as a mechanism to safely reduce the cesarean delivery rate.3 VBAC proved to be an effective 

contributor to reduce the use of cesarean through the early 1990s. From 1990 through 1996, the 

VBAC rate rose from 19.9 to 28.3 percent and the cesarean rate declined from 22.7 to 20.7 

percent.4

 Since 1996, VBAC rates have declined sharply, to the point where over 90 percent of 

women with a prior cesarean will deliver by repeat cesarean. While primary cesarean accounts 

for the largest number of cesarean deliveries, the largest single indication for cesarean is prior 

cesarean accounting for 534,180 cesareans each year, thus the safety of VBAC remains 

important.1 The degree to which cesarean deliveries and VBACs are improving or adversely 

affecting health remains a subject of continued controversy and uncertainty. This systematic 

review was conducted to inform the 2010 NIH Consensus Development Conference to evaluate 

emerging issues relating to VBAC. 

Key Questions 

The key questions reviewed in this report were assigned by the Agency for Healthcare 

Research and Quality. Questions were based on deliberations of the planning committee for the 

National Institutes of Health Consensus Development Conference on Vaginal Birth After 

Cesarean: New Insights convened by the National Institutes of Health’s Office of Medical 

Applications of Research and further refined by a technical expert panel during the evidence 

report process. Ultimately, four key questions were reviewed for this report: 

1.	 Among women who attempt a trial of labor after prior cesarean, what is the vaginal 

delivery rate and the factors that influence it? 

2.	 What are the short- and long-term benefits and harms to the mother of attempting trial of 

labor after prior cesarean versus elective repeat cesarean delivery, and what factors 

influence benefits and harms? 

3.	 What are the short- and long-term benefits and harms to the baby of maternal attempt at 

trial of labor after prior cesarean versus elective repeat cesarean delivery, and what 

factors influence benefits and harms? 

4.	 What are the critical gaps in the evidence for decision-making, and what are the priority 

investigations needed to address these gaps? 

Methods 

Relevant studies were identified from multiple searches of MEDLINE®; DARE; the 

Cochrane databases (1966 to September 2009); and from recent systematic reviews, reference 

lists, reviews, editorials, Web sites, and experts. Retrieved abstracts were entered into an 

electronic database (EndNote®). 

1 
Of the 3,134 citations reviewed from the searches, 2,171 met exclusion criteria at the abstract 

level and were not reviewed further. After the abstract review process, 963 full-text papers were 

retrieved and reviewed for inclusion. An additional 37 full-text papers were retrieved from peer 

review. A total of 203 full-text papers met inclusion after applying paper inclusion/exclusion 

criteria. Investigators quality rated included studies, and those rated good or fair quality are 

discussed in this report. For the topics presented, 71 studies provided data on trial of labor (TOL) 

and VBAC rate, 27 on induction of labor (IOL) or augmentation, 28 on predictors of TOL and 

VBAC, 14 on scored models for predicting VBAC, 41 on maternal outcomes, 11 on infant 

outcomes, 28 on uterine rupture, 19 on abnormal placentation, seven on obesity, 12 on multiple 

cesarean deliveries, and seven on direction of cesarean delivery scar. 

Results 

Among women who attempt a trial of labor after prior cesarean, what 

is the vaginal delivery rate and the factors that influence it? 

Who attempts a trial of labor? The rates of TOL are highly variable, ranging from 28 to 70 

percent with an overall rate of 58 percent in the U.S. The evidence is largely limited to large 

tertiary teaching hospitals. TOL rates have declined, particularly after 1996, both inside and 

outside of the U.S. In the U.S. studies that initiated enrollment after 1996, less than half (47 

percent) of women had a TOL. TOL is more likely in hospitals with higher delivery volumes, 

tertiary care centers, and teaching hospitals. Women with a prior vaginal delivery or non-white 

women were more likely to have a TOL (odds ratio 1.51 to 6.67 and odds ratio 3.5, respectively). 

What is the vaginal delivery rate? In 43 U.S. based studies, 74 percent of women who had 

a TOL delivered vaginally. While TOL rates reported in observational studies have dropped over 

time, VBAC rates have remained constant for the women who have a TOL. 

What are the factors that influence the vaginal delivery rate? All scored predictive 

models provide reasonable ability to identify women who are good candidates for VBAC, but 

none have discriminating ability to consistently identify women who are at risk for cesarean 

delivery. 

Antepartum factors 

Prior vaginal delivery: A prior history of vaginal delivery was consistently reported to 

increase likelihood of VBAC approximately three fold (range odds ratio 1.83 to 28). Among 

women requiring induction of labor, limited evidence also suggests a higher rate of VBAC 

among those with prior vaginal delivery (OR 6.8; 95 percent CI: 3.04 to 13.9). 

Indication for prior cesarean: Women with prior cesarean delivery for 

malpresentation/breech were more likely to have a VBAC (75 percent, range 60 to 86 percent) 

compared with women with prior cesarean delivery for fetal distress (60 percent, range 49 to 69 

percent) or failure to progress/cephalopelvic disproportion (54 percent, range 48 to 60 percent). 

Race: Hispanic and African American women were more likely to have a TOL but less likely 

to have a VBAC compared with non-Hispanic and white women, respectively (20 to 49 percent). 

Location: Women at rural and private hospitals had a decreased likelihood of TOL and a 

decreased likelihood of VBAC (57 percent versus 66 percent for tertiary care centers). 

Macrosomia: There was decreased likelihood of VBAC in infants weighing 4,000 grams or 

greater (odds ratio 0.62; 95 percent CI: 0.54 to 0.71). Infants weighing 4,500 grams or greater 

were less likely to be delivered via VBAC (1.3 to 5.8 percent) compared with 4,000 to 4,499g 

infants (11.6 to 17.4 percent). 

2 
Body mass index: VBAC rates ranged from 68 to 77 percent in the studies of obese women. 

Women with a body mass index (BMI) of less than 40 had VBAC rates of 52.1 to 70 percent. 

Intrapartum factors 

Progress of labor: A greater progress of labor--as determined by more advanced dilation, 

lower station, and higher Bishop score--predicted a higher likelihood of VBAC. 

Epidural: The effect of epidural use on the likelihood of VBAC is uncertain. 

Augmentation: Augmentation of labor with oxytocin was associated with a rate of 68 percent 

VBAC, although the strength of this evidence was low. 

Induction: Sixty-three percent of women with IOL had a VBAC (PGE2=63 percent, 

oxytocin=62 percent, misoprostol=61 percent). Fifty-four percent of women induced with a 

Foley Catheter had a VBAC. 

What are the short- and long-term benefits and harms to the mother of 

attempting trial of labor after prior cesarean versus elective repeat 

cesarean delivery, and what factors influence benefits and harms? 

What are the short-term benefits and harms to the mother of TOL versus elective repeat 

cesarean delivery (ERCD)? 

Maternal death. While maternal mortality is rare, with an overall rate of 10.1 per 100,000 

for all women with prior cesarean, the risk of maternal mortality is significantly increased with 

ERCD (3.8 per 100,000 for TOL versus 13.4 per 100,000 ERCD). When limited to term studies, 

the maternal mortality was 1.9 per 100,000 for TOL and 9.6 per 100,000 for ERCD. 

Hysterectomy. Hysterectomy was rare, occurring in less than three percent of all women 

with prior cesarean. There was no significant difference between the TOL and ERCD with 

respect to hysterectomy among all studies or when studies were limited to term populations; 

however hysterectomy was more common among women undergoing ERCD among studies that 

were open to all gestational ages (GAs). 

Transfusion/hemorrhage. When limited to term studies, the rate of transfusion for TOL was 

6.6 per 1,000 (95 percent CI: 2.0 to 22.1 per 1,000) and for ERCD was 4.6 per 1,000 (95 percent 

CI: 1.6 to 13.2 per 1,000). In term patients, TOL is associated with increased risk of transfusion. 

When all GAs are evaluated, there is an increased risk of transfusion with ERCD, suggesting a 

risk-modifying effect of preterm delivery on risk of transfusion. In low risk ERCD, there was a 

statistically significant increase in transfusion with TOL compared with ERCD prior to labor. 

Spontaneous labor may be protective against hemorrhage, but data are inconsistent. 

Infection. For any GA cohorts, the risk for any infection with TOL was 46 per 1,000 (95 

percent CI: 15 to 135 per 1,000) and for ERCD was 32 per 1,000 (95 percent CI: 13 to 73 per 

1,000). The rate for fever with TOL was 65 per 1,000 (95 percent CI: 44 to 93 per 1,000) and for 

ERCD was 72 per 1,000 (95 percent CI: 25 to 189 per 1,000). Studies that did not report TOL 

outcome (VBAC or repeat cesarean delivery [RCD] after a TOL) tend to report increased febrile 

morbidity associated with TOL. Cesarean delivery, either ERCD or RCD after a TOL, appears to 

have a higher incidence of any febrile morbidity compared with VBAC but definitive studies are 

lacking. A trend toward increased endometritis was seen with ERCD compared with TOL; in 

contrast, chorioamnionitis was increased in TOL compared with ERCD. Increasing BMI was 

associated with increased fever in patients undergoing TOL. 

Surgical injury. Rate of surgical injury may be increased with TOL, but definitive studies 

are lacking. Vertical skin incision increases risk of surgical injury to the bladder. 

3 
 

Length of stay. Elective repeat cesarean delivery is associated with a longer hospital stay 

compared with TOL. The mean length of stay for TOL was 2.55 days (95 percent CI: 2.34 to 

2.76 days) compared with 3.92 days (95 percent CI: 3.56 to 4.29) for ERCD. 

Uterine rupture. The risk of uterine rupture for all women with a prior cesarean delivery 

regardless of route of delivery is 0.3 percent (95 percent CI: 0.2 to 0.4 percent). The risk of 

uterine rupture for women undergoing a TOL is significantly elevated at 0.47 percent (95 percent 

CI: 0.28 to 0.77 percent); compared with women undergoing an ERCD (0.026 percent; 95 

percent CI: 0.009 to 0.082 percent). 

Maternal morbidity. To date, there have been no maternal deaths reported because of uterine 

rupture. The risk of hysterectomy due to uterine rupture ranged from 14 to 33 percent. 

Neonatal morbidity. The overall risk of perinatal death due to uterine rupture was 6.2 

percent. The two studies of women delivering at term that reported perinatal death rates report 

that 0 to 2.8 percent of all uterine ruptures resulted in a perinatal death. Overall, the literature 

relating to response time between premonitory signs of uterine rupture and perinatal mortality 

are insufficient. However, there is suggestion that fetal bradycardia is an ominous sign for fetal 

extrusion, which is associated with poor perinatal outcomes, and prompt delivery in this setting 

is warranted. 

What factors influence the incidence of uterine rupture? 

Direction of scar. Women with a prior classical incision are at increased risk of uterine 

dehiscence/rupture. Compared with women with prior low transverse cesarean delivery (LTCD), 

women with prior low vertical cesarean delivery (LVCD) or with an unknown scar are not at a 

significantly increased risk of uterine dehiscence or rupture. 

Induction of labor. The risk of rupture with any IOL method at term was 1.5 percent and 1.0 

percent when any GA was considered. At greater than 40 weeks, the rate was highest at 3.2 

percent. 

Gestational age. Relative to women with spontaneous labor, there was no increase in risk of 

rupture among those induced at term. Women induced after 40 weeks GA had an increased risk 

compared with those undergoing spontaneous labor (risk difference 1.8 percent; 95 percent CI: 

0.1 to 3.5 percent, NNH 56). 

Method of induction. The rate of uterine rupture by induction method--oxytocin, PGE2, and 

misoprostol--was 1.1 percent, two percent, six percent, respectively. The risk of uterine rupture 

with mechanical methods of IOL is understudied. 

Can uterine rupture be predicted? Studies of individual factors that may increase or decrease 

a woman’s risk of uterine rupture are largely exploratory. 

Protective factors. Women with prior vaginal delivery have lower risk for uterine rupture. 

Risk factors. Women undergoing IOL have higher risk of uterine rupture compared with 

spontaneously laboring women. Women who are postdate may have a higher risk of uterine 

rupture. Obese and morbidly obese women are more likely to suffer rupture and/or dehiscence. 

Women with a prior classical incision are at increased risk of uterine rupture. 

Predictive measures. No study was able to produce a reliable and robust model to predict 

uterine rupture. This is likely because uterine rupture is a rare event, and although there are 

factors associated with uterine rupture, none are of great magnitude. An accurate and reliable 

tool to predict an individual woman’s risk of uterine rupture has not been found. 

Imaging. The data regarding ultrasound measurements of uterine thickness and uterine 

rupture consistently suggest that there may be value to ultrasound measurements of uterine 

thickness for women with prior cesarean delivery. 

4 
What are the long-term benefits and harms to the mother of TOL versus ERCD? 

Adhesions. Prior cesarean delivery was associated with a statistically significant increase in 

adhesions at subsequent cesarean and hysterectomy. Adhesions were associated with increased 

perioperative complications, time to delivery, and total operative time. It is unclear whether 

adhesions and complications increase with increasing number of prior cesareans. 

General health. No studies evaluated TOL and/or RCD with respect to pelvic pain, risk of 

ectopic pregnancy, and general health risks, such as diabetes or high blood pressure. 

Fertility. Two studies have shown impaired fertility following cesarean delivery. One study 

found a difference in the ability to conceive in subjects undergoing cesarean delivery compared 

with instrumented vaginal delivery (odds ratio 0.33; 95 percent CI: 0.12 to 0.98). Another study 

found a history of cesarean delivery was associated with increased odds of taking greater than 1 

year to conceive (odds ratio 1.53; 95 percent CI: 1.09 to 2.14). 

Menopause. One case-control study found an increased risk of early menopause in women 

with multiple cesarean deliveries compared with no pelvic surgery (odds ratio 2.69; 95 percent 

CI: 1.16 to 6.22). 

What are the long-term benefits and harms to the mother of multiple cesarean? Women 

who do not have a TOL will undergo RCD and, potentially, multiple cesareans. 

Hemorrhage/transfusion. The overall rates of hemorrhage/transfusion with multiple 

cesarean deliveries were less than five percent, but the risk appeared to increase with increasing 

numbers of cesareans. 

Adhesions. The incidence of adhesions increased with increasing numbers of cesareans. 

Surgical injury. Bladder, bowel, and ureteral injury are uncommon occurrences that appear 

to increase with multiple cesareans. 

Infection. The risk of postoperative infection with multiple cesareans remains unclear. 

Wound complications. The risk of wound complications does not appear to increase with 

multiple cesarean deliveries. 

Hysterectomy. There was a strong correlation between multiple cesareans and hysterectomy. 

The odds ratio for hysterectomy with one prior cesarean was 0.7 to 2.14, with one or more was 

1.4 to 7.9, and two or more was 3.8 to 18.6. 

Abnormal placentation 

Abruption. The risk of abruption for women with any prior cesarean was 0.10 to 0.15 

percent. The risk did not appear to increase with prior cesarean or number of prior cesarean 

deliveries. 

Previa. Women with a prior cesarean delivery had a statistically significant increased risk of 

placenta previa compared with women with no prior cesarean at a rate of 12 per 1,000 (95 

percent CI: 8 to 15 per 1,000). The incidence increased with increasing number of prior cesarean 

deliveries. Prior cesarean was a significant risk factor for maternal morbidity in women with 

previa. Compared with previa patients without a prior cesarean delivery, women with one prior 

cesarean and previa had a statistically significant increased risk of blood transfusion (15 versus 

32.2 percent), hysterectomy (0.7 to 4 percent versus 10 percent), and composite maternal 

morbidity (15 versus 23 to 30 percent). For women with three or more prior cesarean deliveries 

and previa, the risk of hysterectomy and composite maternal morbidity rose significantly (0.7-4 

percent versus 50-67 percent and 15 versus 83 percent, respectively). 

Accreta. The incidence of placenta accreta rose with increasing number of prior cesarean 

deliveries. The results were statistically significant for women with two or more prior cesareans 

(odds ratio 8.6 to 29.8). 

5 
Previa and accreta. Women with placenta previa are at increased risk for placenta accreta, 

and the risk increased with increasing number of prior cesareans. Women with more than three 

prior cesareans and previa had a 50-67 percent incidence of accreta. 

What are the short- and long-term benefits and harms to the baby of 

maternal attempt at trial of labor after prior cesarean versus elective 

repeat cesarean delivery, and what factors influence benefits and 

harms? 

What are the short-term benefits and harms to the baby of maternal attempt at TOL versus 

ERCD? 

Perinatal death. Perinatal, fetal, and neonatal mortality rates were low in women with a 

history of prior cesarean delivery. The overall perinatal death rate with TOL was 1.3 per 1,000 

(95 percent CI: 0.59 to 3.04 per 1,000) compared with 0.5 per 1,000 (95 percent CI: 0.07 to 3.82 

per 1,000) for ERCD. The intrapartum death rates were consistently slightly higher in women 

who attempt a TOL (0.1 to 0.4 per 1,000) versus ERCD (0 to 0.04 per 1,000). Women with highrisk conditions and indicated repeat cesarean delivery (IRCD) appear to have higher rates of 

neonatal mortality. 

Sepsis. Three studies measured sepsis in the neonate undergoing a TOL versus ERCD; 

however only one study actually defined and measured “proven” sepsis. This study found no 

differences in proven sepsis in infants born after TOL versus those delivered by ERCD. 

Apgar scores. Four studies found no differences in Apgar scores of less than six and seven at 

5 minutes in infants undergoing a TOL versus ERCD. Three studies examined the differences in 

low Apgars (less than seven) at 5 minutes in VBAC versus RCD after a TOL; two of these 

studies found no difference in Apgar scores of infants born by VBAC versus RCD after a TOL. 

Neonatal intensive care unit (NICU) admission. Six of eight studies found no significant 

differences in frequency of NICU admissions between TOL and ERCD. 

Breastfeeding. No studies were found that explored the effect of a TOL versus an ERCD on 

breastfeeding initiation or continuation. 

Additional short-term outcomes. There was insufficient evidence to determine if rates of 

respiratory distress, neonatal trauma, or asphyxia/hypoxic-ischemic encephalopathy varied 

between TOL and ERCD. 

Factors related to outcomes. There was insufficient data to determine that fetal presentation 

or gestational age in term neonates influences benefits or harms to the neonate undergoing TOL 

versus ERCD. 

What are the long-term benefits and harms to the baby of maternal attempt TOL versus 

ERCD? 

Perinatal outcome in future pregnancies. One study showed that prior cesarean delivery 

increases the risk for unexplained stillbirth in the next pregnancy and another study showed no 

difference in risk for stillbirth. Both studies are limited by their retrospective design and relied on 

large perinatal databases while employing various methodologies to overcome confounding. 

Neurological development. No studies were found that measured the impact of a TOL 

versus ERCD on neonatal neurological development. 

Discussion 

While cesarean deliveries represent a third of all births, they account for almost half of the 

childbirth-related expenses of hospitalization, at $7.8 billion annually.1

 A major contributor to 

the increase in cesareans is the rapid decline in VBACs witnessed over the last decade. 

6 
Therefore, the appropriate and safe use of cesarean and VBAC is not only an individual patientand provider-level concern, but it is also a national health policy concern. 

One of the major findings of this report is that the best evidence suggests that VBAC is a 

reasonable and safe choice for the majority of women with prior cesarean. The occurrence of 

maternal and infant mortality for women with prior cesarean is not significantly elevated when 

compared with national rates overall of mortality in childbirth. The majority of women who have 

TOL will have a VBAC, and they and their infants will be healthy. However, there is a minority 

of women who will suffer serious adverse consequences of both TOL and ERCD. While TOL 

rates have decreased over the last decade, VBAC rates and adverse outcomes have not changed 

suggesting that the reduction is not reflecting improved patient selection. Sophisticated statistical 

models have not been able to predict those women who will do well and those who will be 

harmed. 

The most dramatic change since the 1980 VBAC report is the number of women with 

multiple cesareans. This report found that women with three or more prior cesareans are at 

significantly increased risk of complications, and the risks increase for women with prior 

cesarean delivery and previa. Since we are unable to determine which women will have previa or 

to prevent its occurrence, all pregnant women are at risk, and the risk increases with multiple 

cesareans. 

Studies of VBAC versus ERCD have traditionally reported outcomes based upon actual route 

of delivery rather than intended route, leading to misclassification of patients who intend elective 

repeat cesarean but go into labor prior to their cesarean or women who intended trial of labor but 

who are delivered by cesarean. The evidence from these studies is at best indirect and difficult to 

apply to a woman who plans for either option. Each leaves clinicians and patients uncertain of 

the ramification for their decisionmaking and masks potential adverse effects of desiring one 

route of delivery but having another. 

Mode of delivery for subsequent pregnancies poses a difficult question for women with prior 

cesarean and their providers. Some women have already made their decision prior to leaving the 

hospital after their cesarean, due to factors surrounding that birth. Others will decide early in 

pregnancy, and still others will remain undecided until presenting in labor. Some women will not 

have a choice due to provider, hospital, insurance, or medico-legal factors that mandate repeat 

cesarean. This report suggests that although there are statistically significant differences between 

ERCD and TOL, there are very few clinically significant differences, and the overall mortality 

risk is not significantly elevated between women with prior cesarean delivery and women 

undergoing their first pregnancy. Serious deficiencies were found in the existing literature, 

however, and this report provides a list of research priorities as prioritized by national experts as 

well as potential study designs to advance the field and provide important information to 

patients, clinicians, and policymakers. 

7 
Evidence Report 

1

 1

 

Chapter 1. Introduction 

The effective and safe use of cesarean delivery has been a focus of national attention and 

concern for decades. Thirty years ago the National Institutes of Health (NIH) held a Consensus 

Conference on Cesarean Childbirth in response to concerns about a three-fold increase in the rate 

of cesarean deliveries (from 5 to 15.2 percent).3, 5, 6 As a result of that conference, vaginal birth 

after cesarean (VBAC) was proposed as a mechanism to reduce the use of cesareans. As shown 

in Figure 1, though it took almost a decade following the conference to gain popularity, VBAC 

effectively contributed to the reduction in the cesarean rate. As the VBAC rate rose from 19.9 

percent in 1990 to 28.3 percent in 1996, the cesarean delivery rate decreased from 22.7 percent 

to 20.7 percent over the same time period.4 However, a complex combination of emerging 

studies that suggested that the morbidity associated with VBAC, particularly uterine rupture, was 

higher than initially thought; organizational changes; and liability pressures resulted in a rapid 

reduction in the practice of VBAC and concomitant increases in cesarean delivery. While 

primary cesarean accounts for the largest number of cesarean deliveries, the largest single 

indication for cesarean is prior cesarean, accounting for over a third of all cesareans; thus the 

safety of VBAC remains important.1

 Despite the national goal, as stated by Healthy People 20107 

to reduce the cesarean delivery rate to 15 percent of births, the cesarean delivery rate for 2007 is 

the highest ever recorded, at 32.8 percent of all births.1 This systematic review was conducted to 

inform the 2010 NIH Consensus Development Conference on emerging issues relating to 

VBAC. 

Appendixes and evidence tables cited in this report are available at http://www.ahrq.gov/downloads/pub/evidence/pdf/vbacup/vbacup.pdf. 

1111
 
Figure 1. Rates of vaginal birth after cesarean (VBAC rate), total cesarean deliveries (CD rate), primary cesarean de

and repeat cesarean delivery (RCD)8, 9 

Rate 

95% 85% 75% 65% 55% 45% 35% 25% 15% 

5% 

1989 VBAC data added to birth certificates 

1995 ACOG guideline* 

1996 Landmark paper† 

1999 ACOG guideline‡ 

2001 Landmark paper 

1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 

Year 

VBAC Rate CD Rate Primary CD RCD 

*ACOG guidelines from 1995 states “In the absence of contraindications, a woman with one previous cesarean delivery uterine incision is a candidate for VBAC and should be counseled and encouraged to undergo a trial of labor.” †Landmark paper published by McMahon10 ‡ACOG guidelines from 1999 states “VBAC should be attempted in institutions equipped to respond to emergencies with 

available to provide emergency care.” §Landmark paper published by Lydon-Rochelle, 200111 

12 
 

Structure of Report and Key Questions 

An evidence report focuses attention on the strengths and limits of evidence from published 

studies about the effectiveness and/or harms of a clinical intervention. The development of an 

evidence report begins with a careful formulation of the problem. The Evidence-based Practice 

Center (EPC) systematically reviewed the relevant scientific literature on key questions relating 

to VBAC assigned by the Agency for Healthcare Research and Quality (AHRQ), the Planning 

Committee for the NIH Consensus Development Conference on VBAC: New Insights, the 

National Institutes of Health’s Office of Medical Applications of Research (OMAR), and further 

refined by a technical expert panel (TEP). Ultimately, two background questions and four key 

questions were reviewed for this report: 

Background Questions 

•	 What are the rates and patterns of utilization of trial of labor after prior cesarean, vaginal 

birth after cesarean, and repeat cesarean deliveries in the United States? 

•	 What are the nonmedical factors (provider type, hospital type, etc.) that influence the 

patterns and utilization of trial of labor after prior cesarean? 

Background questions will be addressed in the introduction of the report with information 

from reputable sources; however, these data are not part of the systematic review process. 

Key Questions 

1.	 Among women who attempt a trial of labor after prior cesarean, what is the vaginal 

delivery rate and the factors that influence it? 

2.	 What are the short- and long-term benefits and harms to the mother of attempting trial of 

labor after prior cesarean versus elective repeat cesarean delivery, and what factors 

influence benefits and harms? 

3.	 What are the short- and long-term benefits and harms to the baby of maternal attempt at 

trial of labor after prior cesarean versus elective repeat cesarean delivery, and what 

factors influence benefits and harms? 

4.	 What are the critical gaps in the evidence for decision-making, and what are the priority 

investigations needed to address these gaps? 

Introduction 

The strength and suitability of the evidence regarding the risks of major maternal and infant 

morbidity and mortality associated with VBAC is the focus of this evidence report. In judging 

the suitability of evidence, the perspective taken was what a decisionmaker would want to 

know—that is, whether the risk for complications is higher for women who plan a VBAC versus 

those who plan an elective repeat cesarean delivery (ERCD), under optimal conditions of care. 

Some components of obstetric care, as well as some aspects of the setting of this care, might 

increase the risks of VBAC or ERCD. 

The evidence report emphasizes direct evidence between an intervention (e.g., planned 

VBAC or ERCD) and health outcomes, the quality of individual studies, and the strength of the 

body of evidence, giving weight to studies that are appropriately designed to answer a question 

and meet high methodological standards that reduce the likelihood of biased results. To compare 

two different treatments or management strategies, the results of well-done, randomized 

13 
controlled trials (RCTs) are often regarded as better evidence than are results of cohort, casecontrol, or cross-sectional studies. These designs, in turn, are considered to provide better 

evidence than do uncontrolled trials or case series. However, it is increasingly becoming 

recognized that observational studies may provide important information to aid in understanding 

adverse events when interventions are applied to more heterogeneous populations than are 

typical of RCTs. In addition, studies—particularly trials—of interventions are often conducted in 

narrow populations that are more homogeneous and less generalizable than the intended clinical 

population or they do not include important populations that may be more susceptible to harm. 

Therefore, observational studies that reflect actual clinical effectiveness in more heterogeneous 

populations and community settings can provide information that is more generally applicable. 

Similarly, observational studies can provide quality evidence for assessing diagnostic tests or 

prediction tools. 

Throughout the report, three key comparative effectiveness themes are emphasized: 1) 

understanding whether particular populations have higher likelihood of benefits or harms, 2) 

whether particular settings experience higher benefits or harms, and 3) understanding the role of 

study designs in shaping the understanding of important outcomes or harms from therapies. The 

approach to the evidence not only reports the findings of studies relating to a key question, but 

also looks for information that may illuminate important consequences for the intervention being 

more broadly applied. Sub-questions included in this summary may include: 

•	 Are there important racial, ethnic, socio cultural, genetic, access to healthcare, medical 

utilization, patient values, patient adherence and compliance differences that affect 

response to therapy? 

•	 What populations are particularly susceptible to harm? 

•	 Are the results of effectiveness likely to be retained in populations with more 

heterogeneity, co-morbidities, different age groups, values, preferences, or settings, or 

other characteristics? 

Similarly, this report aims to enhance future research. It is important for researchers to know 

how their choice of study design may affect their results and what elements of study design 

portend higher quality. This report provides these details as a step to informing and improving 

future research. 

Background 

The following were asked as background questions to this evidence report. Information is 

summarized from reputable sources, but did not undergo a systematic review process. 

What are the rates and patterns of utilization of trial of labor after prior 

cesarean, vaginal birth after cesarean, and repeat cesarean delivery in 

the United States? 

Cesarean delivery rates continue to rise in the developed world. A recent report from the 

Organization for Economic Cooperation and Development (OECD) that provides health statistics 

and indicators for 30 countries, reports that the U.S. has one of the highest cesarean delivery 

rates in the world (Figure 2).12 

14 
Figure 2. Cesarean delivery by country - percent for live births (2007)12 

Percent live births 

Note: Data for Norway, Ireland, Australia, United States, and Italy are from 2006 

The cesarean delivery rate in the U.S. reached an all time high of 32.8 percent in 2007, far 

exceeding the national goal of 15 percent.1, 7 Though there are many potential causes, the decline 

in VBACs has certainly contributed to this trend. Cesarean delivery and VBAC rates differ 

considerably by state ranging from 2.5 to 20.9 percent (Figure 3). 

15 
 

Figure 3. Vaginal birth after cesarean rates* by state for 20069 

12.4% 

5.5% 

5.2% 

10.2% 

13.4% 

12% 

18.7% 

8.5% 

17.5% 

10.2% 

4.6% 

7.9% 

10.6% 

2.5% 

9.7% 

7.3% 

9.7% 

14.1% 

2.6% 

16.1% 

9.4% 

5.2% 

5.4% 

4.7% 

8% 5.8% 

6.1% 

7.8% 

3.1% 

7.7% 

12.6% 

10.2% 

11.3% 

5.4% 

12.1% 

4.9% 

5.5% 

13.8% 

13.4% (NH) 

13.1% NYC 

9.8% (no NYC) 

20.9% (VT) 

6.2% (CT) 

6.4% (DC) 

9.8% (DE) 

8.7% (MD) 

8.2% (MA) 

8.8% (NJ) 

8.4% (RI) 

17.7% 

11% 

9.3% 

*Percentage of women with a previous cesarean who then have a subsequent vaginal delivery 

The effects of declining VBAC on cesarean rates are particularly pronounced after 1996. 

When the VBAC rate rapidly began to decline from a high of 28.3 percent in 1996 to its current 

low of 8.7 percent of live births, the cesarean rate climbed by more than 50 percent (from a rate 

of 20.7 percent in 1996, Figure 1).1 Increases in cesarean delivery between 2006 and 2007 were 

reported for all age groups and for the three largest racial groups, white, Black, and Hispanic.8 

The coupling of this trend with a concomitant increase in the primary cesarean delivery rate 

portends a continued escalation in the overall national cesarean delivery rate. 

Both vaginal deliveries and cesareans hold inherent risks. Thus, mothers and clinicians are 

faced with complex decisions and must weigh possible risks and benefits associated with VBAC 

versus ERCD. How these decisions are made could have dramatic effects on the health of 

mothers and their children. 

Patient decisionmaking. Several prior studies reported that up to half (48 percent) of women 

make decisions about a future trial of labor (TOL) before becoming pregnant again.13-17 An 

additional 34 to 39 percent decide to have a TOL by the midpoint of the pregnancy.15, 17, 18 

A prior systematic review13 and several recent studies report that patients’ birth choices are 

complex and are driven by multiple competing factors. Women are balancing perceived health 

risks to themselves and their infants while also processing prior birth experiences and family and 

societal influences.13, 18, 19 Few studies have examined the reasons behind women’s decisions for 

ERCD or VBAC.15, 20 Table 1 lists the reasons behind women’s decisions for ERCD by study. 

16 
 

Table 1. Reasons behind women’s decisions for repeat cesarean delivery 

Study, year Reasons 

Kirk, 199015 Low probability of vaginal delivery 

Avoid pain in labor 

Danger of vaginal birth for mother 

Danger of vaginal birth for infant 

Knew what to expect 

McClain, 199020 Interaction with clinician 

Their reconstruction of the meaning of cesarean 

Personal ideas of motherhood and reproduction 

A woman’s perception of self-efficacy21, 22 and inability to fulfill family obligations22 have 

been cited as reasons for women choosing VBAC. Patient involvement in decisionmaking as 

well as VBAC counseling and educational programs have also been associated with increased 

choice for VBAC, in addition to increased patient satisfaction.23-27 The timing of VBAC 

education seems to be important, with earlier timing of VBAC education in pregnancy being 

associated with higher TOL rates.27, 28 Conversely, two studies, one out of Scotland and one from 

the U.S., found that a lack of education or discussion with their clinician was associated with 

ERCD.23, 29 Interestingly, discussion of uterine rupture does not appear to have undue negative 

influence on patient decisionmaking.29, 30 Studies examining external influences on a woman’s 

choice for VBAC have found that women highly value the opinion of their healthcare provider18, 

23, 29 and to a lesser extent sought input from their partners, family, friends, or other outside 

sources such as the Internet.18, 23 

Decision aids/interventions. Recently, decision aids have emerged to help a woman set 

priorities or understand her childbirth preferences, and ultimately help her make decisions. 

Decision aids are available in several formats: DVDs, paper booklets, and interactive computer 

or Web-based decision aids. Studies of VBAC decision aids have shown that they reduce a 

woman’s decisional conflict and increase knowledge scores; however, their impact on actual 

decisionmaking is uncertain.31-34 

What are the nonmedical factors (provider type, hospital type etc) that 

influence the patterns and utilization of trial of labor after prior 

cesarean? 

Despite increasing evidence to inform women and clinicians about the medical benefits of a 

TOL versus ERCD, the rate of TOL attempts continue to decline.8

 Nonmedical factors that 

influence the patterns and utilization of TOL after cesarean delivery are numerous, yet relatively 

little research has been devoted to acknowledging and understanding their influence on the 

patterns and utilization of TOL after prior cesarean delivery. Nonmedical factors that have been 

suggested to contribute to this decline include professional liability concerns, professional and 

institutional polices, patient insurance type, as well as provider and patient attitudes.35, 36 

Medical liability and provider decisionmaking. Examination of closed malpractice cases 

for obstetricians and midwives indicates that VBAC is an important cause of obstetric lawsuits 

for maternity providers.37-40 According to a recent American College of Obstetricians and 

Gynecologists (ACOG) professional liability survey, 91 percent of obstetric and gynecologic 

physicians responding to the survey reported that they experienced at least one liability claim in 

their career and 62 percent of those claims related to obstetric care.37 More than half of 

17 
respondents reported making changes in their practice due to the availability or affordability of 

malpractice insurance with 19.5 percent reporting increasing their cesarean rate, 19.0 percent 

decreasing their VBAC rate, 21 percent decreasing their number of high-risk pregnant patients, 

and 6 percent stopping obstetric practice entirely. 

Though the studies are few, the literature generally supports the association between 

medical-legal pressures and both increased likelihood to perform cesarean deliveries and reduced 

likelihood to perform VBACs.37, 41-43 Both regional and hospital malpractice claims have been 

associated with higher cesarean delivery rates. One study of hospitals in New York reported that 

the odds of cesarean delivery were three times higher in high premium regions compared with 

low premium regions (95 percent CI: 2.13 to 4.24).41 Similarly, higher hospital-level claims were 

significantly associated with higher cesarean rates after controlling for clinical risk (1.26; 95 

percent CI: 1.10 to 1.43), and physicians’ perceptions of risk of suit was also associated with 

almost a two-fold increased odds of cesarean (1.96; 95 percent CI: 1.53 to 2.93). One study 

demonstrated that for each annual $10,000 increase in medical liability insurance premium, the 

primary cesarean rate increased by 15.7 per 1,000 for term nulliparous women.42 Looking 

specifically at tort reform, caps on noneconomic damages were the leading predictor of delivery 

method, in one study, with VBAC rates being significantly higher and cesarean delivery rates 

significantly lower in states where caps on noneconomic damages existed. A dose response of 

sorts was found among noneconomic tort caps suggesting that noneconomic caps at $250,000 

would be associated with 9,000 additional VBACs and 12,000 fewer cesarean deliveries.43 

Overall the literature supports a connection between malpractice liability and even provider 

perception of risk of liability and use of cesarean. 

Several studies have tried to understand providers’ attitudes toward TOL after a prior 

cesarean delivery.44-49 These studies note disparity in the management approaches of providers in 

women who desire a TOL as well as a perceived increased risk of liability when caring for 

women who attempt a VBAC. Upon examination of 109 closed malpractice claims from a single 

liability insurer, Clark et al concluded that 80 percent of VBAC lawsuits were potentially 

avoidable by a management style that limited VBAC to spontaneously laboring women without 

repetitive moderate to severe variables.39 Some authors have suggested checklists, structured 

guidelines, and simulation of obstetric emergencies to enhance consistency and reduce adverse 

events, but to date, there is insufficient evidence about their effectiveness.50-52 

More recently, reports of limited access to hospitals and providers willing to provide a TOL 

after a previous cesarean have emerged.25 Much of this decline in VBAC services is thought to 

be in response to a shift in professional and hospital guidelines indicating that “VBAC should be 

attempted in institutions equipped to respond to emergencies with physicians immediately 

available to provide emergency care.”53 Smaller hospitals with limited staff and resources have 

difficulty meeting these requirements, interpreted as in-house presence of obstetric surgical 

providers, and many institutions have discontinued offering VBAC services. Declines in rural 

hospitals offering TOL after cesarean have resulted in VBAC services becoming centralized, 

many times far away from where women live and work.54 In a descriptive, comparative study, 

Misra et al found that VBAC attempts had declined in Maryland from 2000 to 2005 (4.65 versus 

3.58 percent, respectively) while the total (primary and repeat) cesarean rate rose from 21.71 

percent in 1995 to 24.03 percent in 2005.55 In a study of all institutions (N=312) providing birth 

services in a four state region, Roberts et al found 30.6 percent of hospitals previously offering 

VBAC services prior to the 1999 ACOG policy recommendation had ceased doing so.56 This 

study also found that access to VBAC services in smaller or more rural hospitals was 

18 
disproportionately affected. The ethical, social, and financial implication of women delivering 

subsequent pregnancies by cesarean because of limited options for a TOL after cesarean delivery 

within their community is unstudied. 

Several studies have explored the relationship between private and public health insurance 

and VBAC.57-59 Wagner et al found that Medicaid insured women were more likely than 

privately insured women to attempt a TOL (64 versus 50 percent, p=0.001) and to have a VBAC 

(62 versus 60 percent, p=not significant [NS]).58 In a recent review of state Medicaid coverage 

and utilization of cesarean delivery, Grant found that an increase in the amount physicians are 

reimbursed for cesarean deliveries versus vaginal delivery does account for a slight increase in 

the number of cesareans being performed.59 Specifically, a $1,000 increase in the reimbursement 

for performing a cesarean increases cesarean delivery rates by 1 percent. A major factor that 

distinguishes VBAC from ERCD is the labor process that could take hours to days and requires 

constant provider supervision. The current structure for provider reimbursement reimburses the 

delivery event (e.g., vaginal versus cesarean delivery) rather than the process. No studies were 

found that addressed the effect of this structure of reimbursement on provider’s willingness to 

offer VBAC. 

In summary, the nonmedical factors that influence the patterns and utilization of TOL after 

prior cesarean delivery are numerous and complex. Studies consistently suggest that these 

nonmedical factors play an important role in decisionmaking and patient access. A better 

understanding of nonmedical issues and the significance of their impact on utilization of VBAC 

is warranted. 

19 
1

 1

 

Chapter 2. Methods 

Topic Development 

Analytic Framework and Key Questions 

The Planning Committee for the National Institutes of Health (NIH) Consensus Development 

Conference on Vaginal Birth After Cesarean (VBAC): New Insights determined the key 

questions for this evidence report. Key questions examine 1) a chain of evidence about factors 

that may influence VBAC, 2) maternal and infant benefits and harms of attempting a VBAC 

versus an elective repeat cesarean delivery (ERCD), and 3) factors that may influence maternal 

and infant outcomes. Figure 4 presents an analytic framework that illustrates the clinical logic 

and contextual factors that underlie the key questions of this report. An analytic framework is 

intended to illustrate relevant clinical logic and other influencing factors, in this case relating to 

VBAC. It is meant to clarify the context in which decisions about route of delivery are made, 

clarify direct and indirect associations, and clarify assumptions and disagreements that underlie 

clinical controversies. Thus, the analytic framework serves as a central conceptual model for 

what information is being sought (key questions), what the literature tells us, and the information 

gaps between the two. 

The framework starts with the population of interest, in this case women with a prior 

cesarean delivery. It explicitly aims to understand a woman’s initial intended route of delivery 

and the factors that influence that initial intention. During this evolving decisionmaking process, 

there may be adverse outcomes that arise from discordance between an initial preference and the 

actual choices available, or there may be unforeseen benefits. The routes of delivery are listed in 

some detail with respect to features that may contribute uniquely to risks and benefits. The 

framework then clarifies the relationship among the route of actual delivery, intermediate 

outcome measures, and maternal and infant health outcomes. This framework represents both 

what might be found in the literature and also important considerations for consumers, clinicians, 

payers, policymakers, and future research. Studies that measure health outcomes, such as 

maternal and infant mortality, are emphasized over studies of intermediate outcomes (e.g., 

nonreassuring fetal tracing). Studies providing evidence of a direct association between an 

intervention (e.g., ERCD) and health outcomes are said to provide direct evidence and are given 

greater weight than are studies that provide indirect evidence. 

Appendixes and evidence tables cited in this report are available at http://www.ahrq.gov/downloads/pub/evidence/pdf/vbacup/vbacup.pdf. 

21
 
Pregnant women 

with a prior CD 

Health Outcomes -Maternal -Inf ant 

Intended delivery route -TOL -ERCD 

Actual delivery route -VBAC -Assisted spontaneous -ERCD, labored -ERCD, unlabored -IRCD, labored -IRCD, unlabored 

Intermediate outcomes -Maternal (e.g. UR, breastfeeding) -Infant (e.g., Apgar) 

Influences 

-Healthcare system/hospital policy -Social (including family) -Environment/setting -Medical/obstetrical condition -Cultural -Legal 

Future Pregnancies 

1 2, 3 2, 3 

1, 2, 3 

1, 2, 3 

Figure 4. Analytic framework 

4 

Key Questions 

1. Among women who attempt a trial of labor after prior cesarean, what is the vaginal delivery rate and the factors that influen2. What are the short- and long-term benefits and harms to the mother of attempting trial of labor after prior cesarean versus ecesarean delivery, and what factors influence benefits and harms? 3. What are the short- and long-term benefits and harms to the baby of maternal attempt at trial of labor after prior cesarean vrepeat cesarean delivery, and what factors influence benefits and harms? 4. What are the critical gaps in the evidence for decision-making, and what are the priority investigations needed to address thAbbreviations CD=cesarean delivery, ERCD=elective repeat cesarean delivery, IRCD=indicated repeat cesarean delivery, TOL=trial of laborupture, VBAC=vaginal birth after cesarean 
Technical Expert Panel and Expert Reviewers 

A technical expert panel (TEP) (Appendix A) was assembled at the start of the evidence 

report process to provide input from experts and clinicians in the field to ensure that the scope of 

the project addressed important clinical questions and issues. The panel included 

obstetrician/gynecologists, internists, pediatricians, family physicians, and researchers. The panel 

convened for periodic conference calls during the course of the project. Expert reviewers 

(Appendix B), including several panel members, provided comments on the draft evidence 

report. 

Literature Search and Strategy 

Relevant studies were identified from searching MEDLINE, Database of Abstracts of 

Reviews of Effectiveness (DARE), and the Cochrane Database of Systematic Reviews and 

Controlled Trials (1966 to September 2009) multiple times over the course of the project 

(Appendix C). Additional articles were obtained from recent systematic reviews, reference lists, 

reviews, editorials, hand searching, Web sites, and by consulting experts. Retrieved abstracts 

were entered into an electronic database (EndNote®). 

A total of 3,134 unique citations were reviewed from the searches. Two investigators 

reviewed a random set of titles and abstracts to select articles for full text review. When an 

appropriate level of reliability was reached for inclusion/exclusion of studies, the remaining titles 

and abstracts were divided up and reviewed by one investigator. A research assistant tracked the 

inclusion status and names of reviewers for each abstract reviewed. The full text articles of 

citations that had original data about maternal and infant outcomes relevant to a key question in 

one or more topic area were retrieved. 

Inclusion and Exclusion Criteria 

The target population includes women of reproductive age in the United States (U.S.) with a 

prior cesarean delivery who are eligible for a trial of labor (TOL) or ERCD. Settings that were 

applicable to a U.S. population were included. Therefore, studies were not limited to the U.S.; 

foreign studies were included if originating from a developed country (Appendix D). This was 

believed to offer the broadest range of information on maternal and infant outcomes applicable to 

the U.S. population. The evidence report emphasizes the patient’s perspective in choice of mode 

of delivery, interventions needed for induction and/or augmentation of labor, and potential 

adverse effects of a specific mode of delivery on maternal and infant outcomes. It also considers 

the generalizability of efficacy studies performed in controlled settings. 

The Planning Committee for the NIH Consensus Development Conference identified their 

ideal population of interest as term infants (greater than or equal to 37 weeks gestational age 

[GA]). However, after initial review of the searches, there was concern about the lack of data on 

term-only infants. Two cohort studies that compared outcomes of term infants with preterm 

infants were reviewed and showed no difference.60, 61 For both of these reasons, general 

population studies of women with a prior cesarean delivery who delivered at any GA (preterm 

and term) were included as were studies that focused exclusively on women delivering at term. 

While this approach was thought to be reasonable for maternal outcomes, infant outcomes are 

affected by prematurity, and the scope of studies for this topic remained limited to term studies, 

except where noted. 

23 
General 

For all key questions, full text studies with data on women with a prior cesarean delivery 

eligible for a TOL or ERCD and maternal and/or infant outcomes were initially reviewed. They 

were subsequently included if they met eligibility criteria: 10 or more subjects, participants 

represented the target population, and data on benefits and harms to the mother or infant given 

either mode of delivery. Exclusions included studies of women without a prior cesarean delivery, 

nulliparous patients, breech delivery, exclusive focus on preterm delivery, low birth weight, 

studies of pregnancies including twins or abortions, studies begun or published before the 1980 

NIH Consensus Conference on VBAC, and studies focusing on patients with particular 

conditions such as gestational diabetes, human immunodeficiency virus, preeclampsia, etc. 

(Appendix E). Non-English language papers, editorials, letters, studies available exclusively in 

abstract form, and studies of animals or cadavers were also excluded. Case-control and case 

series studies meeting similar inclusion/exclusion criteria were examined and included if they 

reported relevant data. Given that the focus of this report is intended for a U.S. obstetric 

population, studies conducted in undeveloped or developing countries were excluded (Appendix 

D). If the authors described their country as “developing” in either the abstract or the article, it 

was excluded. For a full listing of excluded studies, please see the excluded studies list in 

Appendix F. 

Investigators read the full text version of the retrieved papers and re-applied the initial 

eligibility criteria. For all topics, articles were excluded if they did not provide sufficient 

information to determine the methods for selecting subjects and for analyzing data. For some 

topics, additional criteria were applied to select studies that were systematically reviewed. 

For the purposes of this report, the term “rate” is used to describe the proportion of women 

who experienced a given event (i.e., VBAC, ERCD, etc.). Though this is not always technically 

correct when expressing summary statistics, it is a term that is used throughout the literature and 

easily understood by patients and clinicians. 

Among women who attempt a trial of labor after prior cesarean, what 

is the vaginal delivery rate and the factors that influence it? 

For this question, full text randomized controlled trials (RCTs) were reviewed in addition to 

observational studies. This key question was limited to studies with data on women with a prior 

cesarean delivery having a TOL and vaginal delivery rates and/or factors influencing the delivery 

rate. For evaluating the rates of TOL and VBAC, studies were included if they explicitly stated 

the inclusion and exclusion criteria and provided data for computing TOL or VBAC rates. 

To evaluate the effect of induction of labor (IOL) on women with a prior cesarean delivery, 

only studies that reported the number of women who were induced and the corresponding 

number with VBAC, uterine rupture, or other relevant outcome were included. Of particular 

interest were those studies that stratified data by the method of IOL, or whether oxytocin was 

used for IOL or augmentation or both. We included RCTs and observational studies, preferring 

cohort designs with an inception cohort but also including less rigorous designs (case series) 

because data from RCTs and cohort studies were sparse. 

24 
What are the short- and long-term benefits and harms to the mother of 

attempting trial of labor after prior cesarean versus elective repeat 

cesarean delivery, and what factors influence benefits and harms? 

For this question, the ideal comparison group was intended VBAC versus intended ERCD. 

However, as no studies of health outcomes measured intent, the primary comparison groups were 

TOL and ERCD, unless otherwise noted. 

An important concern for patients, providers, hospitals, and policymakers regarding VBAC is 

the potential for uterine rupture, which can have severe maternal and infant morbidity and 

mortality. To determine how frequently uterine rupture occurs, it is important to have a clear 

definition for uterine rupture. A prior systematic review of VBAC and uterine rupture found that 

studies varied widely in their definition and use of terminology surrounding uterine rupture.62 

This report uses the anatomic definition of uterine rupture that was proposed by the prior 

evidence report and restated by the TEP for this project. For the purposes of this report, uterine 

rupture is defined as: 

•	 Complete Uterine Rupture – separation through the entire thickness of the wall including 

visceral serosa (with or without extrusion of part of all of fetal-placental unit) 

•	 Incomplete Uterine Rupture – separation that was not completely through all layers of the 

uterine wall (e.g., serosa intact)62 

To evaluate the effect of IOL on the outcome of uterine rupture, the definitions given above 

were used in the primary analysis. Because the number of studies using these definitions was 

small, the scope of literature was expanded to enable examination of individual factors predicting 

uterine rupture, predictive tools, and imaging to predict uterine rupture. 

What are the short- and long-term benefits and harms to the baby of 

maternal attempt at trial of labor after prior cesarean versus elective 

repeat cesarean delivery, and what factors influence benefits and 

harms? 

For this question, all studies were limited to term infants (greater than or equal to 37 weeks 

GA), with the exception of fetal macrosomia and perinatal mortality. Studies addressing the 

influence of fetal macrosomia used fetal weight (greater than or equal to 4,000 grams) for the 

inclusion criteria instead of GA. 

To measure the frequency of perinatal mortality and the corresponding subsets of perinatal 

death, we used the definitions accepted by the National Center for Vital Statistics.63 The 

definition of perinatal death (perinatal II) included infants less than 28 days of age and fetal 

deaths of 20 weeks or more GA. To study the frequency of stillbirth (antepartum and 

intrapartum) we used both the intermediate and late fetal definitions of fetal death. Intermediate 

(20-27 weeks GA) and late fetal death (greater than or equal to 28 weeks GA) referred to the 

intrauterine death of a fetus before delivery. Although most fetal deaths occur early in pregnancy 

(less than 20 weeks GA), most countries, and in particular the U.S., only report intermediate and 

late fetal death. Neonatal (infant) mortality was defined as death in the first 28 days of life.63 

Rates for perinatal, fetal, and neonatal mortality were reported per 1,000 live births. 

25 
To better understand the relationship between perinatal morbidity and mortality with fetuses 

or infants born to women with a prior cesarean delivery, we excluded studies that did not exclude 

cases with congenital or lethal anomalies (before or after analyses). If it could be determined in 

the analysis or discussion section of a study which perinatal deaths were owed to congenital 

anomalies, we retained the study for inclusion (excluding the deaths attributed to anomalies). To 

reduce the effects of prematurity on the neonatal mortality rate, we limited our analyses of 

neonatal mortality to term infants. 

What are the critical gaps in the evidence for decisionmaking, and 

what are the priority investigations needed to address these gaps? 

For this question, investigators reviewed the synthesis of their results and compiled a list of 

relevant areas that were lacking in evidence. During the expert review process, reviewers were 

asked to prioritize the gaps identified by the investigators. Specifically, experts were asked if 

stated topic areas were of low, medium, or high priority for future research and to provide 

additional clarification on their positions. Areas rated as highest priority, meaning 50 percent of 

the experts rated the domain as high, are discussed in this section. 

Special Considerations 

There are topics of interest that do not easily fall into the key questions, these include: effect 

of maternal obesity, multiple cesarean deliveries, and direction of cesarean scar on outcomes. For 

the effect of maternal obesity on outcomes, full text papers were excluded if the prior cesarean 

delivery group was not broken out in TOL analysis, VBAC rates were not provided by body 

mass index (BMI) or weight categories, or if BMI or weight were used as one of many predictors 

(e.g., regression model, modeling study) without other usable analysis. For the multiple cesarean 

deliveries, studies were included that specified maternal outcome by number of cesareans. 

Outcome by exact number of prior cesareans were identified when possible. For the direction of 

cesarean scar, studies were limited to those that identified direction of scar and specified 

outcomes by scar direction. 

Data Extraction and Synthesis 

All eligible studies were reviewed and a “best evidence” approach was applied, in which 

studies with the highest quality and most rigorous design are emphasized.64 Data were extracted 

from each study, entered directly into evidence tables, and summarized descriptively. Benefits 

and adverse effects of mode of delivery were considered equally important and both types of 

outcomes were abstracted. 

Studies were included in the synthesis of the evidence report if they achieved a good or fair 

quality rating as determined by study design, methods, and analysis. When possible, original data 

were used as presented in the article. When necessary, raw numbers were calculated from given 

percentages. Data were pooled from studies evaluating the same outcomes of interest. All results 

are reported as percentages to allow the reader to make direct comparisons of frequency. 

Because many of the adverse outcomes are rare, percentages were also translated into rates 

consistent with those reported in vital statistics, for example maternal death is reported per 

100,000, while hysterectomy, infection, fever, transfusion, incidence of placenta previa by 

number of prior cesareans, neonatal mortality, and perinatal mortality are reported per 1,000. 

26 
Several included studies came from the National Institute of Child Health and Human 

Development Maternal-Fetal Medicine Units Network (MFMU) cohort (Appendix G). For 

synthesis, the most appropriate study is included for the outcome being discussed. 

Studies that did not use an anatomic definition for uterine rupture were excluded from 

analysis of rates of uterine rupture. For other topic areas where studies that used an anatomic 

definition were not available (predictors, imaging to predict uterine rupture, and timing from 

symptom to delivery as a predictor of infant outcome), information was provided from existing 

studies. 

Quality Rating of Individual Studies 

Reviewers rated the quality of RCTs, cohort, case-control, and case series studies using 

criteria specific to different study designs developed by the U.S. Preventive Services Task Force 

(U.S.PSTF) and additional criteria developed by the National Health Service Centre for Reviews 

and Dissemination, based at the University of York in England (Appendix H).65, 66 Two 

reviewers independently reviewed a small portion of the studies. When reviewers disagreed, a 

final rating was reached through consensus. When a Kappa of at least 0.60 was met between 

reviewers, a single reviewer rated the remaining studies.67 The Kappa between reviewers for this 

evidence report was 0.743 (95 percent CI: 0.537 to 0.949). Studies reporting several different 

outcomes may have different quality ratings for each outcome depending on how accurate the 

measure used was and how completely it controlled for potential confounders in multi-variable 

models (Appendix I). Studies determined to be poor quality were not included in the analyses, 

unless no studies of better quality were available for a given topic. 

In addition to the quality criteria for each study design, the evaluation of prediction modeling 

studies required that they provided a clear definition of prognostic factors. The most important 

criteria for these studies were comparable groups that included clear inclusion and exclusion 

criteria; clear definitions of the prognostic factors; and adjustment (as needed, for studies without 

comparable groups) for confounders. To achieve a rating of good, minimally, the study had to 

meet these three ratings. A study with comparable groups and no need for adjustment could still 

meet this standard. For studies that only met two of these three criteria, the highest quality rating 

they could achieve was fair. 

Development of Evidence Tables and Data Abstraction Process 

The following information about the patient population, study design, study outcomes, and 

study quality was extracted from full text, published studies of VBAC and TOL, IOL, ERCD, or 

uterine rupture and was used to construct evidence tables showing: identifying information 

(study name, years of observation); setting (population-based, referral clinic-based, other); study 

design (randomized trial, prospective, etc.); interventions (induction, augmentation medications); 

outcomes studied (infant, maternal, cost, etc.); length of followup; statistical methods for 

handling confounders (statistical adjustment, stratification, none) and attrition; numbers of 

subjects recruited, included, and completing study; and characteristics of the sample 

(demographic variables, number of previous births, other risk factors). Data were abstracted by 

one reviewer and verified by a second. 

For prediction studies, odds ratios are routinely presented unless noted by another measure of 

risk (relative risk [RR]). When possible all results are presented using the same reference and 

outcome. In the prediction sections, the results are presented for predicting TOL and for 

27 
predicting VBAC. If a study, for example, predicted repeat cesarean delivery after a TOL, the 

odds ratios were inverted so that all studies predicted VBAC. 

Strength of Available Evidence 

We assessed the overall strength of the body of evidence for each key question using the 

methods described in the Methods Reference Guide for Effectiveness and Comparative 

Effectiveness Reviews used by the Evidence-based Practice Centers.65 The purpose of grading 

the strength of the whole body of evidence is to provide information beyond study design 

hierarchy and internal validity assessment to other factors that are important to the application of 

information for clinical practice and policy. Parameters thought important to policymakers 

include quantity of evidence, assessment of risk of bias, precision, directness, and consistency. 

Risk of bias was assessed in two ways: first by describing the study designs used and assuming a 

hierarchy of designs in terms of risk of bias (randomized controlled trials inherently having 

lower risk of bias than do observational study designs) and secondly by reporting the cumulative 

internal quality rating of the included studies. In order to have low risk of bias, the studies would 

be both RCTs and also have good internal quality ratings overall, and bodies of evidence that are 

based on observational studies with poor internal quality ratings would be determined to have a 

high risk of bias. Moderate risk of bias would be the many combinations of factors that would 

fall in between these two extremes. Consistency was evaluated by determining if the majority of 

study results were trending in a similar direction, such that their point estimates and confidence 

intervals (CI) may vary, but the overall conclusions are similarly evaluable. The directness of the 

evidence was assessed by whether there was a direct link between the interventions studied and 

the outcomes of interest; for example if mortality due to uterine rupture is the outcome of 

interest, did the studies evaluate these in the same study or were separate bodies of evidence 

required to answer the question. Precision refers to how sure one can be of the point estimate of 

effect and was assessed by examining the narrowness of CIs of studies or CI of the point 

estimate resulting from pooled analysis. The body of evidence was graded for the evidence 

surrounding the most important outcomes in the report. A table was created presenting the 

ratings for each of these domains for the following maternal outcomes: VBAC rate, IOL rate 

(with subcategories of VBAC rate, uterine rupture rate, and other harms–stratified by 

intervention), maternal mortality, rate of uterine rupture, hysterectomy, transfusion, hemorrhage 

and blood loss, effect of IOL on hemorrhage, infection, and long-term sequelae (adhesions, 

pelvic pain, and reproductive health). The following infant outcomes are also captured on the 

table: perinatal, fetal, and neonatal mortality; transient tachypnea of the newborn (TTN); 

respiratory morbidity with bag-and-mask ventilation; respiratory morbidity with intubation for 

meconium; hypoxic-ischemic encephalopathy/asphyxia; neonatal intensive care unit (NICU) 

admissions; neurologic sequelae (short- and long-term); sepsis; trauma; and breastfeeding 

(Appendix J). From the assessments of the domains described above, an overall grade of the 

strength of the body of evidence was determined (high, medium, low, or insufficient). A high 

strength of evidence reflects a high degree of confidence that the body of evidence presents the 

true effect and suggests that additional studies and future research would have a low likelihood 

of changing the estimate. A moderate strength of evidence suggests that the confidence in the 

body of evidence is moderate and that additional studies may change the estimate. A low 

strength of evidence suggests that the confidence that the body of evidence is reflecting the true 

estimate is low and that it is likely that new studies may change the estimate. An insufficient 

28 
strength of evidence suggests that there is either no evidence or that the body of evidence does 

not permit estimating the true effect. 

Data Synthesis 

In addition to discussion of the findings of the studies overall, meta-analyses were conducted 

to summarize data and obtain more precise estimates on main outcomes for which studies were 

homogeneous enough to provide a meaningful combined estimate. Otherwise, the data are 

summarized qualitatively. 

For common events, e.g., TOL and VBAC, where normal approximation applies, estimates 

of rates and their standard errors were calculated from each study and directly combined. A 

random effects model68 was used to combine the studies while incorporating variations among 

studies. Statistical heterogeneity was assessed by using the standard Q-test and the I

2

 statistic 

(the proportion of variation in study estimates due to heterogeneity rather than sampling error).69 

Based on the Cochrane handbook, a rough guide to interpret I

2

 is as follows: 

0 to 40 percent: might not be important; 

30 to 60 percent: may represent moderate heterogeneity; 

50 to 90 percent: may represent substantial heterogeneity; 

75 to 100 percent: considerable heterogeneity. 

Furthermore, the importance of the observed value of I

2

 depends on (i) magnitude and 

direction of effects and (ii) strength of evidence for heterogeneity (e.g., P value from the chisquared test).69 The proportion of women in the induced groups who achieved VBAC or who had 

a uterine rupture was combined using MetaAnalyst (Beta 3.13; Tufts Medical Center).70 For the 

other outcomes, the rates were combined using STATA 10.1® (StataCorp, College Station, 

Texas, 2009). 

For rare or relatively rare events—e.g., the number of ruptures, maternal deaths and infant 

deaths, etc.—normal approximation does not apply well to estimates of rates directly, and we 

used two slightly different methods to combine them. When studies did not report zero events in 

the group, we first logit-transformed the rates before combining the studies as the distribution for 

the logits of rates were usually approximately normal. The studies were then combined using a 

random effects model,68 and the combined rates were obtained by transforming the combined 

logit-rates to its original scale. Statistical heterogeneity (Q-test and I

2

 statistic) was assessed 

based on the logits of rates for these outcomes. These analyses were performed by using STATA 

10.1® (StataCorp, College Station, Texas, 2009). When there are studies that reported zero 

events, a logistic random effects model71, 72 was used to include studies without events. This 

model also applies the logit-transformation of the rates to achieve better statistical property. In 

this case, statistical heterogeneity was assessed using Fisher’s exact test, and analyses were 

performed using the NLMIXED procedure in SAS v9.2 (SAS Institute Inc., Cary, NC, USA). 

Risk ratio and/or risk difference were used to compare various rates between TOL and ERCD 

groups. Again the studies were combined by using a random effects model68 and statistical 

heterogeneity was assessed using Q-test and I

2

 statistic. 

Forest plots were presented to graphically summarize the study results and the pooled 

results.73 To explore heterogeneity, we performed subgroup analyses and meta-regression74, 75 to 

evaluate whether the summary estimates differ by study level characteristics. 

29 
Size of Literature 

Of the 3,134 citations reviewed from the searches, 2,171 met exclusion criteria at the abstract 

level and were not reviewed further. After the abstract review process, 963 full text papers were 

retrieved and reviewed for inclusion. An additional 37 full text papers were retrieved during the 

peer review process. After applying inclusion/exclusion criteria, a total of 203 full text papers 

met inclusion. Investigators quality rated included studies, and those rated good or fair quality 

are discussed in this report. As mentioned previously, poor quality studies are not discussed 

unless no studies of better quality were available for a given topic. For the topics presented, 71 

studies provided data on TOL and VBAC rate, 27 on IOL or augmentation, 28 on predictors of 

TOL and VBAC, 14 on scored models for predicting VBAC, 41 on maternal outcomes, 28 on 

uterine rupture, 11 on infant outcomes, 19 on abnormal placentation, seven on obesity, 12 on 

multiple cesarean deliveries, and seven on direction of cesarean delivery scar (Figure 5). 

30 
Review titles/abstracts 

with eligibility criteria 

Database searches* 

downloaded citations 

3,134 

2,171 abstracts excluded 

963 Total full text papers retrieved and 

reviewed with refined eligibility criteria† 

797 full text papers excluded because: - Published <1980 - <10 subjects - From developing or undeveloped cou- No prior CD - Twins or abortions 

37 papers suggested by reviewers and other sources 

Studies that meet all 203

inclusion criteria 

Study meets all inclusion 

criteria, is of good or fair 

quality and is included in 

71 27 28 14 41 28 11 19 

results, stratified by topic ‡ TOL & I/A Predictors Scored Maternal Uterine Infant Abnormal Spe

VBAC of TOL & Models for Outcomes rupture Outcomes Placentation Conside

Rate VBAC Predicting 

VBAC 

* Databases searched include MEDLINE, Cochrane and DARE (see Appendix C for search strategies) 7 1

Figure 5. Search and selection of literature 

† See Appendix E for details on inclusion and exclusion criteria Obesity Mult‡ Many studies are included in more than one topic area 

CD=cesarean delivery; TOL=trial of l CD

abor; VBAC=vaginal birth after cesarean; 

I/A=Induction/Augmentation of Labor 
1

 1

 

Chapter 3. Results 

Among women who attempt a trial of labor after prior 

cesarean delivery, what is the vaginal delivery rate and the 

factors that influence it? 

In the sections that follow for this question, the rate of trial of labor (TOL) and its predictors 

are presented followed by the rate of vaginal birth after cesarean (VBAC) with special focus on 

induction and spontaneous labor. The section closes with a summary of the many factors 

associated with VBAC and a review of tools that attempt to predict VBAC for women who have 

a TOL. 

Trial of Labor Rate 

In order to understand the proportion of women who have a VBAC, the first searches were 

for studies to estimate the proportion of women attempting a TOL in the United States (U.S.). To 

be included studies had to be at least fair quality, clearly define eligibility for TOL, as well as 

provide the number of women eligible for TOL and the number of women who had a TOL. 

Thirty-five observational studies consisting of 10 prospective cohort studies76-85 and 25 

retrospective cohort studies,10, 27, 86-108 were combined providing a TOL rate of 61 percent (95 

percent CI: 57 to 65 percent). This analysis (and all meta-analyses) was conducted using a 

random effects model that considers heterogeneity. In this analysis of 35 observational studies 

that included 661,765 TOL-eligible women, the Q-statistic for heterogeneity was high, with an I

2 

for between-heterogeneity of greater than 99 percent. The full range for TOL rates across the 

studies inside and outside the U.S. was 28 to 82 percent, Figure 6. Further stratification of study 

subgroups were conducted to assess differences that could explain the heterogeneity. Considered 

factors included study design (prospective versus retrospective), U.S. versus non-U.S. 

population, gestational age of the population (term versus any gestational age), and year of study. 

Among these, gestational age, country of origin, and year of study demonstrated statistically 

significant differences. Stratification by the study designs (retrospective and prospective) of all 

35 studies revealed no significant association with TOL rates. 

As shown in Figure 6, the overall TOL rate in studies conducted in the U.S. was 58 percent 

(95 percent CI: 52 to 65 percent), with a range of 28 to 70 percent, compared with 64 percent (95 

percent CI: 59 to 70 percent) among women in studies conducted outside the U.S. 

Appendixes and evidence tables cited in this report are available at http://www.ahrq.gov/downloads/pub/evidence/pdf/vbacup/vbacup.pdf. 

33
 
C 

Interval) Any gestational age 

0.68 (( 0.66, 00 .70) McMahon, 1996 6138 

0.69 (( 0.64, 00 .73) Rozenberg, 1996 642 

0.66 (( 0.62, 00 .71) Strong, 1996 239 

0.69 (( 0.68, 00 .71) Obara, 1998 310 

0.58 (( 0.55, 00 .61) McNally, 1999 888 

0.58 (( 0.58, 00 .59) Rozenberg, 1999 246 

0.69 (( 0.68, 00 .71) Bais, 2001 252 0.68 (( 0.65, 00 .71) Spaans, 2002 214 

0.56 (( 0.56, 00 .57) Cameron, 2004 14350 

0.39 (( 0.38, 00 .39) Locatelli, 2004 1767 

0.55 (( 0.54, 00 .55) Gonen, 2006 1308 

0.61 (( 0.55, 00 .68) Kugler, 2008 1102 

Subtotal 

0.47 (( 0.42, 00 .51) Term
 0.50 (( 0.47, 00 .53) Smith, 2002 24529 

0.68 (( 0.62, 00 .75) Wen, 2004 308755 

0.70 (( 0.65, 00 .74) Smith, 2005 44963 

0.66 (( 0.63, 00 .68) Selo-Ojeme, 2008 215 

0.49 (( 0.48, 00 .49) Pang, 2009 787 

0.28 (( 0.27, 00 .28) Subtotal 

0.54 (( 0.42, 00 .65) 

(Total) overall 

0.58 (( 0.52, 00 .65) 

.2 .4 .6 .8 1 0 .2 .4 .6 

(95% onfidence Study Name N

Figure 6. Trial of labor in studies conducted in the United States and outside the United States 

Trial of Labor in United Trial of Labor in NonStates Studies United States Studies 

Trial of Labor Rate 

Study Name N 

Any gestational age 

Phelan 1987 2643 

Stovall 1987 396 

Pickhardt 1992 471 

Flamm 1994 7229 

Hueston 1994 1001 

Gregory1999 66856 

Socol 1999 3002 

Durnw ald 2004 768 Macones 2005 24175 

Landon 2006 45988 

DeFranco 2007 25065 

Subtotal 

Term
 

Troyer 1992 567
 Hook 1997 989
 

DiMaio 2002 204 

Fisler 2003 449 Loebel 2004 1408 

Hibbard 2006 32399 

Gregory 2008 41450 

Subtotal 

(Total) overall 

0

Trial of labor rate (95%co nfidence interval) Trial of labor rate (95% confidenc
 

 

 

Similarly, fewer women in studies conducted exclusively in term populations both inside and 

outside the U.S. had a TOL, 53 percent (95 percent CI: 47 to 59 percent) compared with 66 

percent (95 percent CI: 61 to 70 percent) for studies that included any gestational age (GA, 

p=0.002). Further stratification by country and by GA (shown in Figure 6) revealed that this 

relationship was present in both U.S. and non-U.S. studies but was only statistically significant in 

studies conducted outside the U.S. (p=0.001). 

Because VBAC rates have changed over time109 with dramatic decreases after 1996 when 

new evidence about uterine rupture was published,10 the studies were grouped by the years when 

the data were collected: completed before 1996; included 1996; started after 1996. Before 1996, 

the summary estimate of the TOL rate in the U.S. was 62 percent (95 percent CI: 58 to 67 

percent).77, 79, 81, 84, 90, 92, 94, 102, 105, 107 The summary estimate for the TOL rate in studies that were 

started before 1996 but completed during or after 1996 was 63 percent (95 percent CI: 55 to 72 

percent).97, 98, 110 Finally, the summary estimate for the TOL rate for studies started and 

completed after 1996 was 47 percent (95 percent CI: 37 to 58 percent).78, 80, 87, 88, 93 Thus TOL 

rates among studies conducted after 1996 were significantly lower than studies conducted prior 

to 1996 (p=0.009) or that included 1996, p=0.036). This pattern was also observed among 

studies conducted outside the U.S., see Figure 7. 

Figure 7. Global trial of labor rates have dropped over time 

United States Studies 

Non-United States Studies 

N Studies 

*

† 

95% Confidence Interval 

*US studies started after 1996 reported lower rates of TOL than studies that included 1996 (p=0.036) or 

were completed by 1996 (p=0.009) 

†Non-US studies started after 1996 reported lower rates of TOL than studies that were completed by 1996 

Trial of labor rate (95% confidence interval) 

(p=0.009). 

Almost all of the TOL studies were conducted in tertiary care centers, teaching hospitals with 

residents and 24-hour anesthesia teams available; therefore, findings have limited applicability to 

rural settings. Because stratification by setting was not feasible, studies that reported rates across 

settings were examined to find information for rural settings. Three retrospective studies10, 86, 94 

reported reduced attempts (TOL rates ranging from 36 to 47 percent) for rural settings compared 

with urban and/or teaching settings (TOL rates ranged from 53 to 64 percent). Consistent with 

35 
this finding, one retrospective study reported that 70 percent of repeat cesarean deliveries (RCD) 

in rural settings were potentially unnecessary compared with 61 percent in urban teaching 

settings.111 

Summary of trial of labor rates. The rates of TOL are highly variable ranging from 28 to 

70 percent in the U.S. The evidence is largely limited to large tertiary teaching hospitals. TOL 

rates have declined, particularly after 1996, both inside and outside of the U.S. In the U.S. 

studies launched after 1996, less than half (47 percent) of women in the studies had a TOL. 

Predictors of Trial of Labor 

Eight good or fair quality retrospective cohort studies,10, 27, 86, 94, 101, 112-114 and one fair quality 

retrospective cross sectional study111 looked for factors known in the prenatal setting that may 

predict TOL. Three themes emerged from these studies related to site of delivery, history of prior 

vaginal delivery, and race. TOL was more likely in hospitals with higher delivery volumes, 

tertiary care centers, and teaching hospitals.10, 86, 94, 111 Women with a prior vaginal delivery had 

more than double the likelihood of a TOL (odds ratio 1.51 to 6.67).10, 86, 101 Finally, non-white 

women were more likely to have a TOL than white women (odds ratio 3.5).27 Further details and 

discussion of predictors of TOL can be found in Appendix K. 

Vaginal Birth After Cesarean Rate 

As the TOL rate is decreasing, it is certainly important to examine what affect, if any, this 

has on the VBAC rate and what factors are contributing to vaginal delivery. Sixty-seven studies, 

14 fair quality prospective cohort studies76-85, 115-118 and 53 retrospective cohort studies60, 86-93, 110, 

119-128 10, 27, 95-98, 100-108, 129-146 provided an overall summary estimate for VBAC of 74 percent (95 

percent CI: 72 to 75 percent). The heterogeneity of this meta-analysis of 67 observational studies 

that included 368,304 women was high, I

2

 greater than 98 percent. The range in VBAC rates 

across studies inside and outside the US was 49 to 87 percent, Appendix L. To examine this 

heterogeneity, these studies were stratified and analyzed by study design (prospective versus 

retrospective; true cohort that included TOL and ERCD versus studies of TOL only), country 

(U.S. versus non-U.S.), GA (term only versus any GAs) and by years when the data were 

collected (completed before 1996, during 1996, and started after 1996). None of these factors 

were found to result in statistically significant differences (see Appendix L for detailed 

evaluation). 

Summary and strength of evidence on vaginal birth after cesarean rates. The overall 

strength of the body of evidence is moderate. The rates of VBAC are highly variable in these 

studies. Most evidence of VBAC rates are from studies based in large tertiary care centers. While 

TOL rates have dropped over time, VBAC rates reported in observational studies have remained 

constant for the women who have a TOL. In studies based in the U.S., 74 percent (95 percent CI: 

72 to 76 percent) of women who had a TOL delivered vaginally. 

Induction of Labor 

A major area of interest is whether clinical antepartum and intrapartum management 

strategies such as induction of labor (IOL) influence VBAC rates. Women with a history of a 

prior cesarean delivery who undergo a TOL may require cervical ripening, induction and/or 

augmentation of labor. Multiple approaches can be taken including mechanical, pharmacological 

or combinations. The potential impact of each method on the ultimate VBAC rate, as well as any 

36 
 

harm or benefit to the mother or infant is important to understand. It is particularly important 

when reviewing medications to consider the impact of type of drug, dose and regimen as well as 

important characteristics of the mother, the labor, and the fetus. Cervical ripening, which is used 

when the cervix is determined to be “unfavorable” for induction (generally a Bishop’s score of 

less than 6), can be accomplished using various mechanical methods including artificial rupture 

of membranes and the introduction of a Foley catheter into the cervix. The pharmacological 

approach to cervical ripening is generally accomplished using a prostaglandin—misoprostol 

(prostaglandin E1 analog) or prostaglandin E2—although the progestin blocker, mifepristone, has 

also been studied. Prostaglandins and oxytocin are used for labor induction, and oxytocin is 

frequently used to augment labor that is not progressing as expected. 

While comparisons are sometimes made between women undergoing IOL to those with 

spontaneous labor, the reasons that induction is necessary may confound any effect of the drug or 

mechanical method of induction. However, the realistic comparison group for women 

undergoing IOL is expectant management as women who present in spontaneous labor are no 

longer candidates for IOL. Women who are induced may have different risk factors for VBAC 

and other outcomes; therefore, the proportion of women with VBAC associated with each 

method of induction is presented as the primary outcome, with comparison to spontaneous labor 

presented as a secondary outcome. Other maternal outcomes were reported inconsistently such 

that meaningful analysis of an association with use of oxytocin was not possible. 

Of 328 studies screened for inclusion relating to intrapartum and antepartum factors, 27 

studies were included in the IOL analysis. The others were not included due to not reporting data 

on induction or augmentation, reporting data on the proportion induced or augmented in the 

overall study population but not stratifying the results on these factors, or because they were 

found to be poor quality. 

Any induction method. Twenty-seven fair quality studies involving 11,938 women report 

on the rate of VBAC among women receiving any type of IOL.60, 96, 118, 125, 130, 131, 139, 141, 145, 147-164 

Combining these data results in a pooled estimate of VBAC with any method of IOL of 63 

percent (95 percent CI: 59 to 67 percent, Table 2, see Appendix M for additional figures). Unlike 

other datasets in this review, these observational studies found very similar proportions of VBAC 

whether or not the population was limited to women with term pregnancies. Table 2 also shows 

the pooled estimates for the individual methods of induction, whose estimates range from a low 

of 54 percent with mechanical methods to a high of 69 percent with mifepristone. 

Table 2. Vaginal birth after cesarean rates by types of induction 

Any 

Induction 

Method Oxytocin PGE2 Misoprostol Mifepristone Mechanical 

% VBAC 63% 62% 63% 61% 69% 54% 

95% CI 58% to 67% 53% to 70% 58% to 69% 27% to 90% 41% to 89% 49% to 59% 

Abbreviations: CI=confidence interval; VBAC=vaginal birth after cesarean 

Prostaglandins. Prostaglandins are used to ripen the cervix and to initiate labor. The two 

prostaglandins that can be used for this purpose are prostaglandin E2, which is available in two 

formulations in the U.S. (Prepidil® gel and Cervidil® insert, both as dinoprostone), and 

misoprostol, which is an analog of prostaglandin E1. In general, the prostaglandins are 

administered cervically or vaginally, with re-application after several hours if cervical ripening 

has not progressed adequately. Oxytocin may be used following cervical ripening, to augment 

37 
 

labor, if the strength or frequency of contractions is not considered adequate to maintain 

sufficient labor. 

Prostaglandin E2. Nineteen studies reported the rates of women with a VBAC after receiving 

prostaglandin E2 for cervical ripening for a TOL. These were a single trial in term pregnancies, 

one case control study, seven cohort studies including women delivering at less than 37 weeks 

GA, four case series of term gestations, and six case series of open GA.139, 145, 147-149, 151, 152, 155, 

157-159, 161, 163, 165-170 Two were poor quality169, 170-- inadequate reporting of numbers of women 

included in analyses and lack of control for potential confounding factors--while the rest were 

fair quality. Also, a nested case-control study did not report data adequately to determine the 

proportion who received PGE2 and had a VBAC.166 Some of these studies compared the women 

with induction with women experiencing spontaneous labor63, 139, 145, 149, 157, 158, 161, 163, 165-169 and 

others made only comparisons among induction groups.147, 148, 151, 152, 155, 159, 170 

Pooling studies with similar design indicates that 63 percent (95 percent CI: 58 to 69 percent) 

of women undergoing a TOL with IOL with PGE2 had a VBAC. One outlier is a very small 

study (N=17)163 that reported a low rate of VBAC for spontaneous labor (33 percent), but 

removing this study does not materially alter the results (Appendix M). 

Examining the pooled analysis (Appendix M), it can be seen that including women induced 

prior to 37 weeks gestation (any GA) appears to reduce the rate of VBAC from 77 percent in 

term patients to 61 percent and 65 percent in any GA (case series and cohort studies); however 

the data on term gestations is limited to two case series studies. What role, if any, study design 

played in vaginal delivery rates was also considered. For this reasons studies are grouped in the 

plot according to study design. As demonstrated by the figure, vaginal delivery rates did not vary 

by study design. 

Additional data on induction with PGE2 come from a trial that compared weekly 

administration of PGE2 (up to three doses) to expectant management. The VBAC rate with this 

weekly regimen was 57 percent compared to 55 percent with expectant management. Because 

this does not reflect usual practice with PGE2, it may not reflect the VBAC rate found with the 

more traditional administration.161 

Dose of prostaglandin was sporadically reported, and when reported was not consistent in the 

reporting metric (e.g., mean number of doses versus the number of women receiving two or three 

doses). Similarly, the number of prior cesarean delivery and the rate of prior vaginal births may 

have influenced the rate of VBAC with PGE2 induction, but these covariates were not reported 

adequately for analysis. A small number of studies did report these variables, but either did not 

stratify the results by specific induction method156 or had too few numbers to allow analysis.157 

Augmentation of labor with oxytocin may be an important confounder for VBAC and might 

be expected to result in improved VBAC rates. The use of oxytocin for augmentation of labor 

after induction with PGE2 ranged widely in the 11 studies reporting these data, from 16 to 77 

percent (Table 3). Examining the rigorousness of the study design, the inclusion of only term or 

any GA labors, or the size of the study does not provide further understanding of any potential 

relationship between these variables. 

38 
Table 3. Vaginal birth after cesarean and proportion with augmented labor in women induced 

with prostaglandin E2 

Study, year Study Design Gestation 

# 

Induced 

with 

PGE2 

% 

VBAC 

% 

Augmented 

Rayburn, 1999161 RCT 

Multicenter 

women desiring VBAC 

Term 143 57 32 

Norman, 1992159 Case series 

Women with 1 prior CD 

Term 30 73 37 

Goldberger, 1989155 Case series 

women with 1 prior CD 

Term 19 84 21 

Yogev, 2004145 Cohort 

women with 1 prior CD 

with IOL 

Any GA 97 64 25 

Ben-Aroya, 2002148 Cohort 

University hospital 

women in 2nd delivery 

following a CD 

Any GA 55 55 16 

Flamm, 1997167 Case series 

Kaiser hospitals 

women with a history of 

CD undergoing TOL 

Any GA 453 51 77 

Locatelli, 2006168 Case series 

University hospital 

women with a previous 

LTCS 

Any GA 310 71 40 

Chilaka, 2004151 Case series 

University hospital, 

women with prior CD, 

who had IOL 

Any GA 130 61 27 

Kayani, 2005157 Case series 

Larger inner city 

teaching hospital, 

women with IOL after 1 

prior CD 

Any GA 149 46 35 

Meehan, 1989158 Case series 

University teaching 

hospital 

women with 1 prior CD, 

nominated for TOL 

Any GA 52 79 44 

Blanco, 1992149 Case series 

University hospital 

women attempting TOL 

Any GA 25 72 20 

Abbreviations: CD=cesarean delivery; GA=gestational age; IOL=induction of labor; LTCS=low transverse 

cesarean scar; TOL=trial of labor; PGE2=prostaglandin E2; RCT=randomized controlled trial; 

VBAC=vaginal birth after cesarean 

Misoprostol. Evidence on the VBAC rate with cervical ripening and induction using 

misoprostol in women with history of prior cesarean delivery is extremely limited. The 

39 
 

contributing evidence comes from two small (N=96 combined) fair quality retrospective cohort 

studies that included women with any GAs. These two studies report widely different 

proportions of women with VBAC, 78 percent171 and 44 percent,172 with a pooled estimate of 61 

percent (95 percent CI: 27 to 90 percent). Although these are fair quality studies in general, they 

may not represent similar populations, or because they are small may not have included enough 

women to be able to prevent sampling error. 

Mifepristone. Mifepristone is a progestin blocker that has been studied for use in cervical 

ripening. A small (N=32), fair quality trial compared mifepristone 200 mg and placebo, each 

given orally for 2 days to women with a Bishop score of three or less, followed 2 days later by 

induction with prostaglandins, oxytocin, and/or artificial rupture of membranes as needed. 

Eligible women were scheduled for IOL due to post-date pregnancy, pre-eclampsia, or severe 

fetal growth retardation. Although the rate of onset of spontaneous labor was higher in the 

mifepristone group than in the placebo group (69 versus 12 percent), the rates of vaginal delivery 

were not statistically significantly different (69 versus 50 percent) although the study may have 

not had adequate statistical power to determine a difference at a p<0.05 level.173 Other findings 

that were different between the groups were the time between first dose and start of labor (60 

hours and 30 minutes versus 82 hours and 50 minutes; p<0.01), and the amount of oxytocin 

required (2.11 international unit [IU] versus 4.67 IU; p<0.01) for mifepristone and placebo, 

respectively. 

Oxytocin. Oxytocin is used for both IOL as well as augmentation of labor when contractions 

are inadequate to maintain progression of labor. Seventeen studies reported on the use of 

oxytocin in women with a prior cesarean delivery (one good quality cohort, nine fair quality 

cohorts, and five fair quality case series).11, 118, 125, 129-131, 141, 154, 156-158, 162, 164, 168, 169, 174, 175 While 

oxytocin can be used in combination with a prostaglandin, the focus here is on the use of 

oxytocin alone. Five studies reported VBAC rates with oxytocin alone used only for IOL (not 

augmentation),125, 141, 157, 162, 175 The pooled estimate of VBAC is 62 percent (95 percent CI: 53 to 

70 percent). From the forest plot (Figure 8) it can be seen that the studies with lower quality 

design and including any GA report higher VBAC rates than either better studies (cohort design) 

or the single case series in term gestations. Additionally, the best quality study in this group 

reported an odds ratio for VBAC of 1.19 (95 percent CI: 0.93 to 1.53) for women who had IOL 

with a favorable cervix compared with women with spontaneous labor.156 It is not clear that this 

includes only oxytocin induction, however. A fair quality study reported a VBAC rate of 74 

percent, but includes oxytocin and/or amniotomy.169 

40 
 

 

(Total) overall

 

 

Figure 8. Vaginal birth after cesarean rates with oxytocin induction 

Study Name N	 VBAC Rate (95%
 

Confidence Interval)
 Any gestational age:
 

case series studies
 

Kayani, 2005 45	 0.756 (0.610, 0.859) 

Paul, 1989 32	 0.719 (0.542, 0.847) 

Overall 77	 0.740 (0.631, 0.826) 

Any gestational age:
 

cohort studies
 

Flamm, 1987 149	 0.557 (0.477, 0.635) 

Sakala, 1990 48	 0.583 (0.441, 0.713) 

Overall 197	 0.563 (0.493, 0.631) 

Term:
 

case series studies
 

0.529 (0.365, 0.688) Silver, 1987 34
 

NaN (NaN, NaN)
 Overall 34 

0.619 (0.531, 0.701) (Total) overall 

1.0 0.1 

VBAC rate (95% confidence interval) 

Abbreviation: VBAC= vaginal birth after cesarean 

Seven studies reported the rate of VBAC with oxytocin used only for augmentation.118, 125, 129, 

131, 141, 154, 162 A fair quality case series reported the odds of a VBAC with oxytocin augmentation 

to be 0.83 (95 percent CI: 0.67 to 1.02) compared with no augmentation.129 The other six studies 

reported data that could be pooled, resulting in a VBAC rate of 68 percent (95 percent CI: 64 to 

72 percent, Appendix M). 

Among studies reporting data on VBAC rate among women receiving oxytocin for induction 

separately from those who received oxytocin for augmentation of labor, three of four found 

higher proportions with VBAC when oxytocin is used for augmentation rather than induction 

(Table 4). Pooling these data indicates a 12 percent increase in absolute risk of VBAC when 

augmentation rather than induction is the reason for oxytocin use. 

41 
 

Table 4. Vaginal birth after cesarean rate with oxytocin used for induction versus augmentation 

Study Study Design Induction Augmentation 

Silver, 1987162 Cohort 

Medical center hospital, women at term with a history 

of one prior CD, who received intrapartum oxytocin 

53% 63% 

Sakala, 1990141 Cohort 

University hospital, women who underwent TOL and 

had > 1 prior CD 

58% 88% 

Flamm, 1987125 Cohort 

Kaiser hospitals, women with prior CD who were 

administered oxytocin 

56% 69% 

Paul/Horenstein, 

1985131 

Cohort 

University hospital, women with prior CD offered TOL 

72% 69% 

Pooled absolute difference in proportion with VBAC 12% (95% CI 0.3% to 24%) 

Abbreviations: CD=cesarean delivery; CI=confidence interval; TOL=trial of labor; VBAC=vaginal birth 

after cesarean 

Dose of oxytocin (cumulative, maximum rate of infusion) was sporadically reported, and 

when reported was not consistent in the reporting metric. Similarly, while the number of prior 

cesarean deliveries may have influenced the rate of VBAC with PGE2 induction, these covariates 

were not reported adequately for analysis. 

Prostaglandin E2 versus oxytocin. While the conditions that may lead to using PGE2 for 

IOL may differ from those for choosing oxytocin, there may be some value in comparing the 

benefits and harms of these two drugs, particularly if the reason for induction and underlying 

obstetric characteristics also can be compared. The best evidence comparing the effect of these 

two drugs on VBAC rates comes from a good quality cohort study of women at term who had 

one prior cesarean delivery.156 In this study of 11,778 women, 3,259 underwent IOL. An analysis 

of women induced with an unfavorable cervix compared with those experiencing spontaneous 

labor showed a significantly lower rate of VBAC in the induced group; odds ratio 0.46 (95 

percent CI: 0.39 to 0.53). A similar analysis of women induced with a favorable cervix found no 

significant difference between groups; odds ratio 1.19 (95 percent CI: 0.93 to 1.53). Assuming 

that PGE2 (+ oxytocin) was used in those with unfavorable cervixes, and oxytocin used without 

PGE2 in those with favorable cervixes, this indicates a higher rate of VBAC with oxytocin alone. 

However, a small proportion of women were induced without either drug and direct comparisons 

were not undertaken. A poor quality trial enrolled 42 women and found a higher rate of VBAC 

with PGE2 (81 percent) compared with oxytocin (71percent); however the study was too small to 

find a statistically significant difference and methodological concerns indicate the need to 

interpret these findings with caution.176 Two other studies (from three publications) did not 

report data in a way that would allow comparison of VBAC between PGE2 and oxytocin

164, 177, 178 groups.

Mechanical methods of induction. The evidence on the risk or benefits of mechanical 

methods of cervical ripening in women with a prior cesarean delivery is limited to five 

studies.148, 150, 169, 179, 180 The best of these are two small retrospective cohort studies evaluating 

the use of a Foley catheter for cervical ripening compared with spontaneous labor.148, 150 The 

proportion of women with VBAC after Foley catheter IOL were 56 percent150 and 51 percent148 

with a pooled proportion of 54 percent (95 percent CI: 49 to 59 percent). 

The first is a good quality study (N=2,479), that also included a group of women with 

favorable cervixes who received amniotomy. Logistic regression controlling for several factors 

found that cervical ripening with a transcervical Foley catheter resulted in a slightly lower 

proportion with VBAC than with spontaneous labor (odds ratio 0.68; 95 percent CI: 0.41 to 

42 
 

1.15), while amniotomy resulted in a slightly higher rate (odds ratio 1.19; 95 percent CI: 0.84 to 

1.69); neither was statistically significantly different from spontaneous labor.150 

The other study (N=1,648) included women who received PGE2 tablets or Foley catheter for 

cervical ripening compared with spontaneous labor.148 This study has more flaws than the first, 

in that the baseline characteristics, such as number or prior cesarean deliveries, previous vaginal 

deliveries, inter-delivery interval, etc., are not as well described; neither was the dosing of PGE2 

taken into account nor did the analysis control for confounding variables. This study found the 

rate of VBAC to be significantly lower in the Foley catheter group compared with the 

spontaneous labor group (51 versus 65 percent, p< 0.01). 

In the first study, crude rates of VBAC were also lower in the Foley catheter group, but 

analysis controlling for confounding factors resulted in a non-significant difference.150 The 

authors of both studies note that for the outcome of uterine rupture, the studies were most likely 

underpowered to find differences between the groups; they estimate that it would require a 

sample size of greater than 10,000 patients to find a difference. Additional evidence on Foley 

catheter, a double-balloon device, and breast stimulation were inadequate to make 

determinations of VBAC rate, risk of uterine rupture, or other outcomes.169, 179, 180 No studies of 

other mechanical methods, e.g., acupuncture, were found. 

Influence of prior vaginal delivery and indication for prior cesarean on vaginal birth 

after cesarean induction. A small case series of women requiring oxytocin induction or 

augmentation (N=98) did not find a significant difference in the rate of VBAC among those with 

prior vaginal deliveries compared with those with none among the group induced with oxytocin, 

but did find that prior vaginal delivery resulted in a higher rate of VBAC among those with 

oxytocin augmentation compared to those with no prior vaginal deliveries (86 and 56 percent, 

p<0.05).162 In this study, a recurrent indication for induction or augmentation resulted in 

significantly lower rates of VBAC compared with the groups without recurrent indications (38 

versus 90 percent, p<0.01 and 81 versus 50 percent, p<0.05, respectively). Comparing the birth 

weights of current and previous deliveries in the induced and augmented groups resulted in a 

non-significant difference with those induced, but a difference favoring smaller fetuses among 

those augmented (84 versus 49 percent, p<0.01). Because this is a small case series, these data 

should be interpreted as suggestive, rather than conclusive. 

In a fair quality study of 205 women with a prior cesarean delivery and who required 

induction, 41 percent of those with no prior vaginal deliveries had a VBAC, while 82 percent of 

those who did have prior vaginal delivery had a VBAC (odds ratio 6.8; 95 percent CI: 3.04 to 

13.9).157 

The relationship between the reason for the prior cesarean delivery and VBAC when 

oxytocin is used was examined in three studies (total N=595).118, 125, 130 The most commonly 

reported indications and pooled proportions with VBAC are listed in Table 5 below. 

Table 5. Most commonly reported indications and pooled proportions 

Indication for Prior cesarean delivery VBAC Rate 

Failure to progress/cephalopelvic Disproportion 54% (48% to 60%) 

Fetal Distress 60% (49% to 69%) 

Malpresentation/breech 75% (60% to 86%) 

Abbreviations: VBAC=vaginal birth after cesarean 

Summary and strength of the evidence on induction of labor. Overall, evidence regarding 

the rate of VBAC among women with IOL is low to moderate strength, indicating that 63 

percent of these women will have a VBAC (PGE2=63 percent, oxytocin=62 percent, 

43 
 

misoprostol=61 percent). Augmentation of labor with oxytocin was associated with a rate of 68 

percent VBAC, although the strength of this evidence is low. Evidence was inadequate to make a 

comparison of VBAC resulting from induction with oxytocin or prostaglandin E2. Fifty-four 

percent of women induced with a Foley Catheter had a VBAC, based on moderate strength 

evidence. Other mechanical methods were not reported adequately to make comparisons or 

conclusions. Approximately 60 percent of the studies were conducted in university hospital 

settings, with the smaller studies also including community hospital settings such that the 

evidence is weighted towards the larger, tertiary care setting. Less than half of these studies were 

conducted in the U.S., with most of the others being conducted in Canada, Britain, Ireland, 

Sweden and Israel. For induction, the results were not stratified by age, race, ethnicity, or 

baseline risk. 

Predictors of Vaginal Birth After Cesarean 

The impact of individual factors on VBAC discussed above can overlap and interact with 

each other such that a factor found to have statistically significant influence on VBAC rate may 

no longer be significant when other key factors are taken into account. Studies that evaluate these 

factors in concert, using regression analyses for example, can provide a higher level of evidence 

on the residual influence of individual factors. Four prospective cohort studies,85, 167, 181, 182 18 

retrospective cohort studies,27, 61, 86, 99, 104, 106, 113, 119, 127, 136, 143, 146, 183-188 and one case-control 

study189 addressed predictive factors for VBAC. The key factors considered by these studies 

were demographic factors that included maternal age, ethnicity, race, and marital status; 

nonclinical factors that included insurance status, site of delivery, and volume of VBACs; past 

obstetric factors that included prior vaginal delivery and prior indications for cesarean delivery; 

pre-existing and current factors that included maternal height, body mass index (BMI), substance 

abuse, and pre-existing maternal disease; and current obstetric factors related to the infant 

gender, age and size. In this section, only the strongest predictors (supported by several good or 

fair cohort studies) that had an overall trend are presented. Full discussion of all predictors can 

be found in Appendix K. 

Demographic factors. Of all demographic predictors that were evaluated, the strongest 

evidence was found for ethnicity and race. In all four cohort studies reporting on ethnicity and 

race, Hispanic women had a reduced likelihood of VBAC (by 31 to 49 percent, Appendix K) 

than non-Hispanic women.181, 182, 185, 187 In these same studies, African American women had a 

reduced likelihood of VBAC (by 20 to 49 percent) compared with white women.181, 182, 185, 187 It 

is interesting to note that non-white women were more likely to have a TOL but less likely to 

have a VBAC.27 While not included in the meta analysis of VBAC rates because the cohort 

included twin deliveries, one retrospective cohort study reported that African American women 

were more likely to fail at VBAC, were more likely to be hypertensive and have diabetes.190 

Nonclinical factors. The site of delivery can play an important role in deciding what kind of 

birthing options are pursued, (Appendix K). Women at rural and private hospitals that provide 

obstetric care for lower risk deliveries had a decreased likelihood of VBAC.86, 111 This finding is 

consistent with another finding by the same investigators86 that women at rural and private 

hospitals were less likely to attempt a TOL. Private hospitals in this study had an average VBAC 

rate of 57 percent compared with a VBAC rate of 66 percent for perinatal centers.86 

Past obstetric factors. There is particular interest in whether demographic factors, 

nonclinical and past obstetric factors may predict VBAC since these factors are known prenatally 

and would allow clinicians to provide information on prognosis early in pregnancy. Investigators 

from studies have explored prior vaginal delivery, years since prior cesarean delivery, prior labor 

44 
 

experience and prior baby weight as potential factors for predicting VBAC. A prior history of 

vaginal delivery was consistently reported to increase likelihood of VBAC in all 13 cohort 

studies86, 99, 104, 127, 136, 143, 167, 181-184, 187, 191 and one case-control study (Appendix K).189 Women 

with a vaginal delivery after their prior cesarean (prior VBAC) were three to seven times more 

likely to have a VBAC for their current delivery127, 167, 181-184, 189, 191 compared with women with 

no prior vaginal deliveries. Women who had a vaginal delivery before their cesarean deliveries 

also had an increased likelihood to have a VBAC.143, 167 

One secondary analysis of a retrospective cohort study98 of 16 community and university 

hospitals123 specifically examined the effect of prior vaginal delivery before a cesarean and of a 

prior VBAC on the current TOL. The VBAC rate for women with no history of vaginal delivery 

was 65 percent, 83 percent for women with a prior vaginal delivery before a cesarean, and 94 

percent for women with a prior VBAC.123 Finally, a secondary analysis of the National Institute 

of Child Health and Human Development Maternal-Fetal Medicine Units Network (MFMU) 

cohort data reported that the likelihood of a VBAC increased with each prior VBAC.192 Women 

with zero, one, two, three, and four or more prior VBACs had likelihoods of VBAC of 63.3, 

87.6, 90.9, 90.6, and 91.6 percent (p<0.001), respectively. 

Pre-existing and current obstetric factors. Many pre-existing factors (maternal height, 

BMI, smoking and substance use, and maternal disease) appear to change the likelihood of 

VBAC (Appendix K) but were only supported by single or two studies and are discussed in the 

appendix. Several investigators examined the effect of pre-existing disease on VBAC. In three of 

four cohort studies, women with a maternal disease (hypertension, diabetes, asthma, seizures, 

renal disease, thyroid disease, or collagen vascular disease) had a decreased likelihood (by 17 to 

58 percent) of VBAC.127, 182, 187 By contrast, in a large prospective study by Grobman et al,181 the 

presence of diabetes, asthma, chronic hypertension, renal disease or heart disease, was not 

significant in the study’s multivariable logistic model. 

Many current obstetric factors related to the infant (GA, birth weight and infant gender) 

predicted VBAC or TOL followed by a cesarean delivery. Of these, the most consistent finding 

is that as infant weight increases the likelihood of VBAC decreases. Four of five studies reported 

that women delivering infants weighing more than 4 kilograms (kg) had a reduced likelihood of 

VBAC (by 41 to 51 percent) than women who delivered smaller infants.86, 127, 143, 146, 182 The 

oldest of these studies143 found no relationship between a birth weight over 4 kg and likelihood 

of VBAC. 

Obstetric factors related to the labor itself (dilation, effacement, station, Bishop score, cervix 

position) consistently predicted VBAC. Three prospective cohort studies,167, 182, 184 one 

retrospective study136 and one case-control study189 provided consistent evidence that women 

who were more dilated at admission or at rupture of membranes (ROM) were more likely to 

deliver vaginally. All three studies that examined effacement reported increased likelihood as 

effacement reached 75 to 100 percent.99, 167, 184 Similarly, all three studies that examined head 

position reported that as the baby’s position was vertex, engaged or at a lower station, the 

likelihood of VBAC increased.85, 136, 185 Both studies that examined Bishop’s score showed that 

as the score increased, the likelihood of VBAC increased two183 to six times.143 

Overall impression of prediction studies. With the exception of three studies,104, 167, 181 

these prognostic studies of VBAC could be described as exploratory.193 According to Simon and 

Altman, studies that report association and identify patients at risk but that have not yet had 

results confirmed in followup studies with pre-stated hypotheses, do not yet provide sufficient 

evidence to change clinical practice.193 The three studies104, 167, 181 that provided this cross45 
validation evidence also proposed screening tools for VBAC and are discussed in detail in 

Appendix N. 

Summary of predictors of vaginal birth after cesarean rate. Hispanic and African 

American women were more likely to have a TOL but less likely to have a VBAC compared 

with non-Hispanic and white women, respectively. Women at rural and private hospitals had a 

decreased likelihood of TOL and a decreased likelihood of VBAC. A prior history of vaginal 

birth was consistently reported to increase likelihood of VBAC. Women delivering infants over 4 

kg have a reduced likelihood of VBAC. Greater progress of labor--measured as greater dilation, 

lower station and higher Bishop score--predicted a higher likelihood of VBAC. 

Screening Tools for Predicting Vaginal Birth After Cesarean

The purpose of a screening tool is to help providers and patients to better identify who will 

have a VBAC (and who is more likely to have a RCD). Currently, most women are told they 

have a likelihood of 60 to 80 percent for a VBAC.194 Screening tools are most helpful for women 

who have an estimate of VBAC outside this range either to discourage or to encourage a TOL. 

Two prospective cohort studies,167, 181 10 retrospective cohort studies104, 107, 116, 120, 122, 128, 142, 143, 

183, 184 and two case-control studies102, 189 that presented screening tools were identified 

(Appendix N). These studies combined individual factors to predict the likelihood of VBAC (or 

RCD) when certain thresholds were reached. Predictive variables (historic, intrapartum or 

perinatal) of delivery route were first identified by univariate analyses. Significant variables 

(p<0.05) were included in multiple logistic regression models and/or scored models. 

In the strongest studies, the resulting models or scoring systems were then evaluated with a 

separate validation dataset.195 Three of the scored models had one or more external validation 

studies that tested the models with independent cohort datasets. The scored model by Flamm167 

was externally validated by one retrospective cohort study.122 The scored model by Grobman 

2007181 was externally evaluated with a retrospective study.120 The Troyer107 model was 

externally validated by two retrospective studies.122, 142 In all validation studies, the scored 

model’s performance was similar to the originally reported performance (see shaded rows of 

Table N-1 in Appendix N). In a retrospective cohort study that evaluated three scored models 

using the same dataset,107, 167, 196, Dinsmoor et al reported that all three models were accurate at 

predicting which women would have a VBAC but were not accurate at predicting who would 

have a RCD after a TOL.122 Using the three models, 50 percent of women with unfavorable risk 

factors had vaginal deliveries, suggesting that other factors may be needed to identify women at 

risk for cesarean delivery. A previous decision analysis of VBAC197 suggested that a scored 

model would be most useful clinically if it achieved a sensitivity and specificity greater than 85 

percent,122 which none of these tools achieved. All scored models are presented and discussed in 

detail in Appendix N. 

Summary of screening tools. Since the VBAC evidence report published in 200362, 194 five 

scored models have been created and evaluated to identify women for VBAC (or for RCD).104, 

128, 181, 183, 184 Two of the studies created scored tools that can be used in the prenatal setting.128, 181 

All scored models provide reasonable ability to identify women who are good candidates for 

VBAC but none have discriminating ability to consistently identify women who are at risk for 

RCD. 

46 
What are the short- and long-term benefits and harms to the 

mother of attempting trial of labor after prior cesarean versus 

elective repeat cesarean delivery, and what factors influence 

benefits and harms? 

This section reviews the maternal benefits and harms associated with VBAC compared with 

ERCD. The goal of this endeavor is not only to describe the current knowledge of risks of each 

type of delivery, but to highlight important gaps in the literature. As part of this report, the 

following outcomes were examined: maternal death, uterine rupture, hysterectomy, transfusion 

and/or hemorrhage, infection, length of hospital stay, surgical injury, and composite morbidity. 

In addition, factors that may modify the outcomes associated with mode of delivery such as IOL, 

number of prior cesarean, deliveries and direction of scar are also discussed. 

Maternal Death 

Maternal mortality rose in the U.S. after the dawn of the 21st century from seven to nine per 

100,000 in the 80s and 90s to 12 to 15 per 100,000 since 2003.198-200 Although these rates are 

still very low, understanding whether choices patients and providers make about route of 

delivery and clinical management contribute to maternal mortality is critically important. 

There were 12 good or fair quality cohort studies totaling 26 maternal deaths among 402,883 

patients that reported maternal mortality associated with TOL and ERCD (Appendix O).76, 77, 81, 

93, 97, 100, 108, 164, 201-204 The absolute risk of maternal death associated with TOL was 0.0038 

percent (95 percent CI: 0.009 to 0.0155 percent) and with ERCD was 0.0134 percent (95 percent 

CI: 0.0043 to 0.0416 percent). Four studies focused exclusively on women delivering at term.93, 

97, 108, 204 Among these four studies the maternal mortality was similarly lower for TOL (0.0019 

percent; 95 percent CI: 0.0004 to 0.0095 percent) compared with ERCD (0.0096 percent; 95 

percent CI: 0.0021 to 0.0432 percent, Figures 9 and 10). 

One study from Canada reported differences in maternal mortality with TOL relative to 

ERCD for low and high volume maternity units. This study deserves mention because it was one 

of the only studies to evaluate maternal death in a range of institution types. This study evaluated 

both large tertiary centers as well as community hospitals, demarcating types by the number of 

deliveries per year.108 In low volume maternity wards defined as less than 500 deliveries a year, 

the odds ratio was 2.68 (0.16 to 45.5) for maternal mortality with TOL compared with RCD. 

High volume maternity wards, defined by greater than 500 deliveries per year, were noted to 

have an odds ratio of 0.16 (0.02 to 1.29) of mortality with TOL compared with RCD.108 No other 

studies stratified maternal death rates by institution size or delivery volume. 

Summary and strength of evidence on maternal death. Overall, the strength of evidence 

regarding the rate of mortality for women with a prior cesarean delivery is high with good 

consistency and precision. While maternal mortality is rare with an overall rate of 10.1 per 

100,000 for all women with prior cesarean, the risk of maternal mortality is significantly 

increased with ERCD. When combining the TOL group across all studies, the risk of maternal 

mortality is found to be 0.0038 percent (95 percent CI: 0.0009 to 0.0155 percent). The combined 

risk for ERCD group across all studies is 0.0134 percent (95 percent CI: 0.0043 to 0.0416 

percent). This translates to 3.8 per 100,000 for TOL (95 percent CI: 0.9 to 15.5 per 100,000) and 

13.4 per 100,000 for ERCD (95 percent CI: 4.3 to 41.6 per 100,000). When the analysis is 

limited to term studies, the combined risk of maternal deaths for TOL is 0.0019 percent for TOL 

47 
(95 percent CI: 0.0004 to 0.0095 percent) and 0.0096 percent for ERCD (95 percent CI: 0.0021 

to 0.0432 percent); translating to 1.9 per 100,000 for TOL (95 percent CI: 0.4 to 9.5 per 100,000) 

and 9.6 per 100,000 for ERCD (95 percent CI: 2.1 to 43.2 per 100,000). In addition, metaregression showed that among TOL studies, maternal mortality was significantly lower among 

studies of term populations compared with studies of any gestational age (p=0.027) but there was 

no significant difference based upon gestational age among ERCD studies (p=0.141) (Figures 9 

and 10). 

While rare for both TOL and ERCD, compared to ERCD, the overall risk of maternal death 

associated with TOL is significantly lower (RR, 0.33, 95 percent CI: 0.13 to 0.88; p=0.027). 

Using 0.0134 percent as the baseline risk for ERCD, the calculated risk difference is -0.0090 

percent (95 percent CI: -0.0117 to 0.0016 percent), translating to 9.0 less deaths per 100,000 (95 

percent CI: 1.6 to 11.7 less deaths per 10,000) from the TOL group. Among the four studies 

focused exclusively on women delivering at term, the maternal mortality risk was similarly lower 

for TOL (RR: 0.27, 95 percent CI: 0.09 to 0.85; p=0.025). Using 0.0096 percent as the baseline 

risk for ERCD, the calculated risk difference is -0.0070 percent (95 percent CI: -0.0087 to 

0.0014 percent), translating to 7.0 less deaths per 100,000 (95 percent CI: 1.4 to 8.7 less deaths 

per 10,000) from the TOL group, as compared to the ERCD group. 

48 
Dea

(95% 

0 000 

Figure 9. Rates of maternal death for trial of labor among all studies 

N Total 

TOL 

D th t (95% C fid I t l) 

D(

N Maternal 

Deaths 

Loebel, 2004 Wen, 2004 Spong, 2007 Gregory, 2008 

Study Name Term studies 

Martin, 1983 Eglington, 1984 Phelan, 1987 Eriksen, 1989 Flamm, 1994 Obara, 1998 Zelop, 1999 Bais, 2001 

Any gestational age studies 

0 0 1 0 1 0 0 0 0 2 1 0 

927 

128,960 

15,323 11,480 

Combined (Test for heterogeneity is based on Fisher’s exact text P=0.443) 

Combined (Test for heterogeneity is based on Fisher’s exact text P=0.521) 

162 308 

1,796 

70 

5,022 

214 

2,774 

184 

0 0 00 00 0 0 0 000 00

All studies combined (Test for heterogeneity is based on Fisher’s exact text P=0.037) 0

0.000 0.002 0.004 0.006 

Death rate (95% confidence interval) 

*95% confidence intervals are exact Abbreviation: TOL= trial of labor 
Figure 10. Rates of maternal death for elective repeat cesarean delivery among all studies 

Any gestational age studies 

N Total 

ERCD 

N Maternal 

Deaths 

Loebel, 2004 Wen, 2004 Spong, 2007 Gregory, 2008 

Study Name Term studies 

0 

10 

5 2 

481 

179,795 

14,993 29,970 

Combined (Test for heterogeneity is based on Fisher’s exact text P=0.013) 

All studies combined (Test for heterogeneity is based on Fisher’s exact text P=0.002) 

Combined (Test for heterogeneity is based on Fisher’s exact text P=0.301) 

Martin, 1983 Eglington, 1984 Phelan, 1987 Eriksen, 1989 Flamm, 1994 Obara, 1998 Bais, 2001 

0 1 1 0 0 0 0 

547 563 847 

68 

2,207 

96 68 

De(950 (00.00.00 (00(00 (00 (00 (00.00.00.00.00.00.0

0.000 0.002 0.004 0.006 

Death rate (95% confidence interval) 

*95% confidence intervals are exact Abbreviation: ERCD= elective repeat cesarean delivery 
Uterine Rupture 

Uterine rupture is a potentially life-threatening complication that has been directly attributed 

to VBAC. By itself, uterine rupture – defined as complete separation through the entire thickness 

of the uterine wall (including serosa) – is a visible or palpable anatomic finding rather than a 

health outcome. However, its association with perinatal and maternal morbidity and mortality 

raises substantial concerns among patients, clinicians, hospitals, and policymakers. Given this, 

there is considerable interest in what populations and conditions make VBAC a reasonable 

option and what if any management factors may reduce either the occurrence of uterine rupture 

or the severity of consequences. This section summarizes studies reporting on the risk of uterine 

rupture for women with TOL and ERCD, the risk of perinatal morbidity and mortality associated 

with uterine rupture, management factors that may contribute to the development of uterine 

rupture or severity of morbidity or mortality associated with uterine rupture, and techniques and 

tools proposed to stratify populations of women with prior cesarean for risk of uterine rupture. 

Risk of uterine rupture. Estimating the risk of uterine rupture for women with a prior 

cesarean has been challenging not only because studies report on actual rather than intended 

route of delivery but also because studies often mixed true anatomic ruptures with asymptomatic 

dehiscences. While numerous studies have been published relating to uterine rupture and/or 

dehiscence (393 articles), only eight cohort studies10, 97, 119, 204-208 were good or fair quality, 

included the population of interest, and used the anatomic definition for uterine rupture contained 

in this report (See Appendix F for a table of excluded studies). Details of the eight included 

studies that included cohorts of either TOL alone or TOL and ERCD together are presented in 

Table 6. 

Table 6. Uterine rupture: trial of labor versus elective repeat cesarean delivery among any 

gestational age studies 

Author Year 

Design/ 

population 

Direction/Number 

Scar N Uterine rupture 

Cahill, 2006205 Retrospective 

Cohort 

17 Community & 

University Centers 

Any number 

LTCD 

Total: 6,619 

TOL: 5,041 

 ERCD: 1,578 

TOL: 20/5,041 (0.40%) 

ERCD: 1/1,578 (0.06%) 

Caughey, 

1999*119 

Retrospective 

Cohort 

1 University 

Hospital 

1 prior 

Any Direction 

TOL: 3,891 TOL: 36/3,891 (0.9%) 

Cowan, 1994206 Prospective Cohort 

TOL only 

Any Number 

Any Direction 

TOL 593 TOL: 5/593 (0.8%) 

Flamm 1988207 Prospective Cohort Any Number 

LTCD or unknown 

scar 

TOL: 1,776 TOL: 3/1,776 (.17%) 

Flamm, 1990208 Prospective Cohort Any Number 

LTCD or unknown 

scar 

TOL: 3,957 TOL: 7/3,957 (.18%) 

Loebel, 2004*97 Retrospective 

Cohort 

1 Community 

Hospital 

1 prior 

LTCD 

Total: 1,408 

TOL: 927 

 ERCD: 481 

TOL: 4/927 (0.4%) 

ERCD: 0 

McMahon, 

199610 Retrospective 

Cohort 

Population based 

Longitudinal study 

1 prior 

LTCD 

Total: 6,138 

TOL: 3,249 

 ERCD: 2,889 

TOL: 10/3,249 (0.31%) 

ERCD: 1/2,889 (0.03%) 

51 
 

 

 

Table 6. Uterine rupture: trial of labor versus elective repeat cesarean delivery among any 

gestational age studies 

Author Year 

Design/ 

population 

Direction/Number 

Scar N Uterine rupture 

Spong, 2007*204 Prospective Cohort 

MFMU 

19 University 

Hospitals 

Any Number 

Any Direction 

Total: 33,037

 TOL: 15,323

 ERCD:17,714 

TOL: 114/15,323 

(0.74%) 

ERCD: 4/17,714 

(0.02%) 

Total 57,419 205 (0.36%) 

* Studies limited to term population 

Abbreviations: ERCD=elective repeat cesarean delivery; LTCD=low transverse cesarean delivery; 

TOL=trial of labor 

Four studies reported uterine rupture outcomes for both TOL and ERCD.10, 97, 204, 205 Among 

these four studies totaling 47,202 patients, there were 154 uterine ruptures; 96 percent (N=148) 

of which were incurred by the TOL group. As shown in Figure 11, these four studies indicate 

that the risk of uterine rupture for all women with a prior cesarean delivery regardless of route of 

delivery is 0.3 percent (95 percent CI: 0.23 to 0.40 percent). 

52 
Figure 11. Uterine rupture among studies including both trial of labor and elective repeat cesarean delivery 

4 

118 

1,408 

33,037 

Term studies 

Loebel, 2004 Spong, 2007 Combined 

Any gestational age studies 

McMahon, 1996 Cahill, 2006 Combined 

11 21 

6,138 6,669 

All studies combined (Test for heterogeneity: Q=4.98, I2=39.8%, P=0.173)† 

TOL + ERCD 

N Ruptures N TOL N Ruptures N TOL + ERCD 

114 

4 

15,323 

927 

10 20 

3,249 5,091 

0.0020.0030.0030.0010.0030.0020.003UterinConf0.0070.0040.0070.0030.0030.0030.004

Term studies 

Spong, 2007 Loebel, 2004 Combined 

Any gestational age studies 

McMahon, 1996 Cahill, 2006 Combined 

TOL 

All studies combined (Test for heterogeneity: Q=13.39, I2=77.6%, P=0.004)† 

0 4 

481 

17,714 

Term studies 

Loebel, 2004 Spong, 2007 Combined 

Any gestational age studies 

McMahon, 1996 Cahill, 2006 Combined 

1 1 

2,889 1,578 

ERCD 

N Ruptures N ERCD 

0 (0, 00.0000.0000.0000.0000.000

All studies combined (Test for heterogeneity is based on Fisher’s exact test: P=0.421) 0.000

*95% confidence intervals are exact † Test for heterogeneity is based on logits of rates 

Abbreviations: ERCD= elective repeat cesarean delivery; TOL= trial of labor 

0.000 0.005 0.010 0.

Rupture rate (95% confidence inte
Within these four studies, the combined risk of uterine rupture for women undergoing a TOL 

is 0.47 percent (95 percent CI: 0.28 to 0.77 percent) and 0.026 percent (95 percent CI: 0.009 to 

0.082 percent) for women undergoing an ERCD. The increased risk for uterine rupture among 

the TOL group is largely affected by the Spong et al study, which reports an occurrence of 

uterine rupture that is double that reported for the other three studies (0.7 percent versus 0.03 to 

0.4 percent).10, 97, 204, 205 Table 7 presents details regarding the four studies that report uterine 

ruptures related to both TOL and ERCD to understand factors that may explain the increased 

risk. The Spong study is the only one to include women with incisional types other than low 

transverse cesarean delivery (LTCD). However, given the small contribution of these other scar 

types to the overall dataset, and the fact that the uterine rupture occurrence among women with 

LTCD in this study was also higher than the other studies (0.75 percent) it is unlikely that this 

alone explains the difference. Fewer women with a prior cesarean delivery elected TOL in this 

study at 39 percent. It is difficult to assess whether the years that studies were conducted affected 

the occurrence of uterine rupture because the two studies conducted after 1996 have very 

different populations.204, 205 Unfortunately, none of the four studies provided details on the 

proportion of women in the study who underwent IOL, a factor that is known to have large 

variation and to increase the occurrence of uterine rupture. The effect of IOL upon uterine 

rupture is considered in detail later in this section. Overall, there is no clear factor that is 

associated with higher versus lower occurrence of uterine rupture among the four studies 

providing comparative data. 

Table 7. Characteristics of uterine rupture studies of trial of labor and elective repeat cesarean 

delivery
 

Author, 

year 

Study 

Population 

Study 

Years GA 

Uterine 

Rupture 

TOL/ 

VBAC 

Direction/ 

# prior 

Prior 

Vaginal 

Delivery IOL 

Cahill, 

2006205 

17 Community 

& University 

Centers 

approximately 

50% 

University 

1996­

2000 

Any TOL 0.4% 

ERCD 0.06% 

77% / 

92% 

8% 

>1prior 

LTCD 

100% NR 

Loebel, 

2004*97 

100% 

Community 

0% University 

1995­

1998 

Term TOL 0.4% 

ERCD 0% 

66% / 

81% 

1 prior 

LTCD 

36-38% NR 

McMahon, 

199610 

7% 

community 

60% tertiary 

1980­

1992 

Any TOL 0.3% 

ERCD 0% 

53% / 

60% 

1 prior 

LTCD 

17% NR 

Spong, 

2007*204 

100% 

University 

1999­

2002 

Term TOL 0.74% 

ERCD 0.02% 

39% / 

73% 

4% >1 

prior 

any 

direction 

49% NR 

Abbreviations: ERCD=elective repeat cesarean delivery; GA=gestational age; IOL=induction of labor; 

LTCD=low transverse cesarean delivery; NR=not reported; TOL=trial of labor; VBAC=vaginal birth after 

cesarean 

Four additional studies reported on uterine rupture exclusively in women undergoing 

TOL.119, 206-208 A sensitivity analysis was performed to examine whether this difference in cohort 

assembly (TOL only versus TOL plus ERCD) affected the results for uterine rupture and there 

was not a statistically significant difference. The increased number of studies available for TOL 

allows a more detailed examination of factors such as gestational age, direction of scar, year of 

study, etc., that may be associated with higher risks of uterine rupture. 

54 
Figure 12. Uterine rupture among all trial of labor studies 

Term studies 

Caughey, 1999 Loebel, 2004 Spong, 2007 

Study Name 

Any gestational age studies 

Flamm, 1988 Flamm, 1990 Cowan, 1994 McMahon, 1996 Cahill, 2006 

36 

4 

114 

N Ruptures 

TOL only 

TOL + ERCD TOL + ERCD 

3,891 

927 

15,323 

N TOL Cohort 

Combined (Test for heterogeneity Q= 2.71, I2= 26.2%, P= 0.258)† 

All studies combined (Test for heterogeneity Q= 36.25, I2= 80.7%, P< 0.001)† 

Combined (Test for heterogeneity Q= 9.12, I2= 56.2%, P= 0.058)† 

3 7 5 

10 20 

1,776 3,957 

593 

3,249 5,091 

TOL only TOL only TOL only 

TOL + ERCD TOL + ERCD 

TOL only studies combined (Test for heterogeneity Q= 22.24, I2= 86.5%, P< 0.001)† TOL + ERCD studies combined (Test for heterogeneity Q= 13.39, I2= 77.6%, P= 0.004)† 

0.000 0.005 0.010 0.015 0.

*95% confidence intervals are exact †All tests for heterogeneity are based on logits of rates 

Abbreviations: ERCD= elective repeat cesarean delivery; TOL= trial of labor 

Rupture rate (95% confidence interval) 
 

As shown in Figure 12, the occurrence of uterine rupture for TOL remains relatively 

unchanged at 0.46 percent. Among TOL studies, the occurrence of uterine rupture is significantly 

higher for studies limited to term patients compared with studies including patients of any GA 

(0.78 versus 0.32 percent, p=0.033). Looking across all eight studies, the highest occurrence of 

uterine rupture among TOL patients were reported by studies that included women with any 

direction of cesarean scar.119, 204, 206 Among these, only Spong et al presented details for uterine 

rupture occurrence according to the direction of incision, with the lowest rate reported in the 

unknown incision group 0.63 followed by LTCD 0.75, classical T or J 1.59 and low vertical 

2.47. There were no uterine ruptures among women who experienced ERCD without labor for 

any direction of incision. This study also provides additional information relative to presence or 

absence of labor and indication for cesarean delivery among the groups because of its unique 

study design. Because it is clinically important to understand the additional risk for uterine 

rupture given both the number and direction of prior cesareans, studies that specifically 

addressed this question are presented in further detail later in this report under the section 

entitled “Special Considerations.” 

Morbidity and mortality related to uterine rupture. As shown in Table 8, there were no 

maternal deaths due to uterine rupture in any of the eight studies.10, 97, 119, 204-208 The risk for 

perinatal death in the event of uterine rupture ranged from 0 to 20 percent with a pooled risk of 

6.2 percent and the highest risk experienced by the TOL group. For perinatal death, it is useful to 

limit to term studies to remove the effect of gestational age. Among the three term studies,97, 119, 

204 two provided data for the risk of perinatal death given uterine rupture.97, 119 They report that 0 

to 2.8 percent of all uterine ruptures resulted in a perinatal death. Figure 13 presents uterine 

rupture related perinatal death among the six studies reporting uterine rupture for populations of 

women delivering at any gestational age.10, 97, 119, 206-208 Four of the eight studies reported the risk 

of hysterectomy given uterine rupture;10, 207-209 only one of which provided comparative data 

between TOL and ERCD groups.10 They reported an occurrence of hysterectomy give uterine 

rupture of 14 to 33 percent. 

Table 8. Rupture associated morbidity 

Author, Year 

Rupture associated 

neonatal deaths 

(% of ruptures) 

Rupture 

associated 

maternal deaths 

Rupture 

associated 

hysterectomy 

Cahill, 2006205 Not reported Not reported Not reported 

Caughey, 1999*119 1/36 (2.8%) 

1 prior CD TOL [timing not 

detailed] 

0 8/36 (22%) 

Cowan, 1994206 0 Not reported Not reported 

Flamm,1988207 0 0 1/3 (33.3%) 

Flamm, 1990208 1/7 (14%) 

Labored at home without 

monitoring; 2 prior CD 

unknown scar FHR 55 at 

admission 

0 1/7 (14%) 

Loebel, 2004*97 TOL: 0 

ERCD: 0 

TOL: 0 

ERCD: 0 

Not reported 

McMahon, 199610 TOL: 2/10 (20%) (no details 

provided) 

ERCD: 0/1 

NR TOL: 2/10 (20%) 

ERCD: 0/1 (0%) 

Spong, 2007*204 Not reported TOL: 0 

ERCD: 0 

Not reported 

*Term studies Abbreviations: CD=cesarean delivery; ERCD=elective repeat cesarean delivery; FHR=fetal heart rate; 

TOL=trial of labor 

56 
Figure 13. Risk for perinatal death given uterine rupture 

Study Name N Perinatal Death N Ruptures Term 

Flamm, 1988 0 3 0 

Flamm, 1990 1 7 0 Cowan, 1994 0 5 0 

2 10 0 

Caughey, 1999 1 36 1 Loebel, 2004 0 4 1 

McMahon, 1996 

All studies combined (Test for heterogeneity is based on Fisher’s exact text P=0.254) 

*95% confidence intervals are exact 

0.0 0.1 0.2 0.3 0.4 Uterine rupture rates (95% confidence interval) 
Summary and strength of the evidence on risk of uterine rupture. Overall, evidence regarding 

the rate of uterine rupture for women with a prior cesarean delivery is moderate in strength, 

indicating that the risk of uterine rupture for women with prior cesarean is 0.3 percent. 

Compared with women undergoing an ERCD, women undergoing a TOL have a significantly 

higher risk of uterine rupture (RR 20.74, 95 percent CI: 9.77 to 44.02; p<0.0010). Using 0.026 

percent as the baseline risk for ERCD, the calculated risk difference is 0.51 percent (95 percent 

CI: 0.23 to 1.12 percent) translating to 5.1 additional ruptures per 1,000 (95 percent CI: 2.3 to 

11.2 per 1,000) women undergoing TOL. Though the studies are limited in number, there does 

not appear to be a reduction in the occurrence of uterine rupture in recent years (e.g., after 1996). 

Overall, studies focused on providing rates of uterine rupture but did not provide important 

details that would provide insights for management—such as the relationship between length of 

labor and uterine rupture—to establish whether there is a dose response for labor. To date, there 

have been no maternal deaths reported because of uterine rupture, and the risk of perinatal death 

due to uterine rupture is similarly low at 6.2 percent. However, the risk of hysterectomy due to 

uterine rupture is an important consideration for women planning VBAC, with rates ranging 

from 14 to 33 percent. There appears to be an increased risk for uterine rupture among women 

who undergo a TOL at term. Because term may also include postdates and inductions, the 

section that follows provides further details on the impact of management and GA upon risk for 

uterine rupture. 

Effect of induction of labor on uterine rupture. Women often need interventions such as 

induction and/or augmentation of labor that may affect a woman’s risk for uterine rupture. Seven 

fair quality studies (four cohort, three case series) including 5,276 women with a prior cesarean 

delivery who had IOL report uterine rupture using the definition of separation through the entire 

thickness of the wall including visceral serosa (with or without extrusion of part of all of fetalplacental unit); two studies of PGE2,

145, 151 one of foley catheter used for cervical ripening,150 and 

four of any IOL method.60, 96, 156, 164 However, one of the studies60 used a definition of rupture of 

extrusion of the uterine contents into the peritoneal cavity, and thus likely underestimates the rate 

of rupture as defined in this report. 

These studies indicate that the risk of uterine rupture is 1.5 percent in women receiving IOL 

and delivering at term and 1.0 percent when women with any GA and receiving IOL are 

included. These rates are two times greater compared with all women with a prior cesarean 

delivering at term (1.5 versus 0.7 percent), and three times greater when considering women with 

any GA (1.0 versus 0.3 percent). Further stratification of the data indicates that there is increased 

risk of rupture in women delivering at greater than 40 weeks GA (Figure 14) compared with 

women delivering at term (3.2 versus 1.5 percent). The reason for induction, the dose of 

induction agents needed, etc., need to be examined more fully to determine the cause of this 

increased risk. The pooled risk of uterine rupture in the spontaneous labor groups in these studies 

is 0.8 percent (95 percent CI 0.7 to 1.1), which is higher than the pooled estimate from all TOL 

studies (0.47 percent; 95 percent CI 0.28 to 0.77 percent), indicating that the baseline risk of 

rupture is higher in the induction studies overall. This is an important factor, suggesting that 

indirect comparisons from these studies to the general TOL studies is not possible. 

58 
 

Figure 14. Uterine rupture with induction of a trial of labor 

Rupture Rate Study Name N (95% Confidence Interval)* < 37 weeks gestational age 

Hammoud 2004 63 0 (0, 0.113) 

Overall 63 NaN (NaN, NaN) 

37 to 40 weeks gestational age 

0.007 (0.002. 0.021) Hammoud, 2004 441 

0.021 (0.009, 0.045) Zelop, 1999 290 

0.013 (0.004, 0.037) Overall 731 

Any gestational age 

Bujold, 2004 672 0.013 (0.007, 0.026) 

Locatelli, 2006 310 0.003 (0, 0.023) 

Yogev, 2004 97 0 (0, 0.076) 

Overall 1,079 0.010 (0.005, 0.021) 

> 40 weeks gestational age 

Hammoud, 2004 181 0.039 (0.019, 0.79) 

Zelop, 1999 270 0.026 (0.012, 0.053) 

Overall 451 0.032 (0.019, 0.053) 

Term 

Grobman, 2007 3,239 0.011 (0.008, 0.015) 

Hammoud, 2004 685 0.015 (0.008, 0.027) 

Zelop, 1999 590 0.023 (0.014, 0.040) 

Overall 4,484 0.015 (0.009, 0.024) 

(Total) overall 0.016 (0.011, 0.022) 

0.001 0.01 0.1 

Uterine rupture rate (95% confidence interval) 

In women delivering at term, the risk of rupture is not statistically significantly greater in 

women undergoing IOL compared with those with spontaneous labor (odds ratio 1.42; 95 

percent CI: 0.57 to 3.52). In examining these studies further, it appears that women at greater 

than 40 weeks GA have increased risk of rupture while those at term or less than 37 weeks GA 

do not (Figure 15). Because there were no ruptures in either group in one study60 an odds ratio 

could not be calculated, but the absolute difference in risk shows that only women delivering at 

greater than 40 weeks GA have an increased risk with IOL over spontaneous labor (risk 

59 
 

 

difference 1.8 percent; 95 percent CI: 0.1 to 3.5 percent). The number needed to harm (NNH) in 

this group is 56 (for every 56 women greater than 40 weeks GA whose labor is induced during a 

TOL, one additional rupture will occur compared with those having spontaneous labor). 

However, for women with indication for induction of labor at 40 weeks gestation and beyond, 

clinicians are faced with the option of induction or ERCD and not spontaneous labor. A better, 

more useful, comparator for induction of labor would be expectant management. These findings 

should be interpreted with caution, as one study found similarly increased rates of rupture with 

induction regardless of GA, while the other found increased risk in the group with greater than 

40 weeks GA only. 

Figure 15. Risk of rupture: induction versus spontaneous labor 

Study Name N 95% Confidence Interval 

< 37 weeks gestational age 

Hammoud 2004 253 0 (-0.023, 0.023 

Overall 253 NaN (Nan, Nan) 

> 40 weeks gestational age 

Hammoud, 2004 329 0.025 (-0.009, 0.059) 

Zelop, 1999 1,271 0.016 (-0.004, 0.036) 

Overall 1,600 0.018 (-0.001, 0.035) 

37 to 40 weeks gestational age 

Zelop, 1999 1,503 0.016 (-0.001, 0.033) 

Hammoud, 2004 1,911 -0.005 (-0.014, 0.005) 

Overall 3,414 0.004 (-0.016, 0.024) 

Any gestational age 

0.002 (-0.008, 0.012) Bujold, 2004 2,479 0.001 (-0.014, 0.016) Yogev, 2004 1,028 0 (-0.004, 0.006) Locatelli, 2006 1,321 0.001 (-0.004, 0.006) Overall 4,828 

Term 

Hammoud, 2004 2,493 0.004 (-0.006, 0.014) 

Zelop, 1999 2,774 0.016 (0.003, 0.029) 

Grobman, 2007 9,228 0.002 (-0.003, 0.006) 

Overall 14,495 0.005 (-0.002, 0.013) 

0.003 (0, 0.007) (Total) overall 

-0.010 -0.005 0.000 0.005 0.010 0.015 0.020 0.025 0.030 

Risk Difference (95% Confidence Interval) 

60 
Given that there is such limited evidence regarding the risk of uterine rupture with various 

methods of IOL, it was decided to evaluate studies that used a broader definition of uterine 

rupture. While these cannot be compared with those evaluated for the risk of uterine rupture in 

spontaneous labor, they can be used to make indirect comparisons across IOL methods. The 

studies included below report that uterine rupture was a primary outcome measure of the study 

and report clear methods for ascertaining rupture, e.g., individual chart review. Because the 

definitions used are not limited to the anatomical description of rupture used in the above, these 

analyses should be considered exploratory only. 

Prostaglandin E2. The risk of uterine rupture with PGE2 use for cervical ripening and IOL 

was reported as a main of outcome interest in 14 studies (six good or fair quality cohort studies, 

and eight fair quality case series). Two of which included only women at term gestation,156, 164 

while the rest included women with any GA.11, 145, 148, 149, 151, 157, 158, 163, 165, 168-170 Pooled analysis 

of the proportion of women experiencing a uterine rupture after PGE2 induction provides a point 

estimate of 2.0 percent (95 percent CI: 1.1 to 3.5 percent, see Figure 16). It is important to note 

however, that these studies did not define uterine rupture according to the anatomic definition in 

this report. Therefore, understanding these rates in comparison with other VBAC studies is not 

possible. The two studies restricting to women with term GA found very different rates; 3.9 

percent164 compared with 0.8 percent.156 The study with the lower rate was methodologically 

superior. The studies with more rigorous design report a higher rate of uterine rupture. One study 

included in this analysis used ICD-9 codes to identify uterine rupture11 – a method that has 

subsequently been shown to overestimate true rupture rates.210 The study reporting the highest 

rate, 10.3 percent,170 identified cases by discharge diagnosis of uterine rupture, another method 

that may overestimate the proportion with true rupture. The validity and reliability of the method 

used was not tested or reported, and similar to the use of ICD-9 codes, could overestimate true 

rupture. Additionally, baseline obstetric characteristics of women induced, mean total dose of 

prostaglandin, and percent receiving oxytocin for augmentation (except for the uterine rupture 

cases) were not reported such that comparisons to other study populations cannot be made. 

61 
       

N

Figure 16. Uterine rupture with prostaglandin E2 induction 

Study Name Uterine Rupture Rate N Case series studies	 (95% Confidence Interval)* 

Blanco, 1992 25 0 (0, 0.244)
 

Chilaka, 2004 130 0 (0, 0.058)
 

Kayani, 2005 149 0.007 (0.001, 0.046)
 

Locatelli, 2006 310 0.003 (0, 0.023)
 

Meehan, 1989 52 0.019 (0.003, 0.124)
 

Umeadi, 2007 17 0.059 (0.008, 0.320)
 

Ardiet, 2005 144 0.021 (0.007, 0.063)
 

Taylor, 2002 58 0.103 (0.047, 0.212)
 

Overall 885 0.019 (0.007, 0.052)
 

Cohort studies 

Ben-Aroya, 2002 55 0 (0, 0.127)
 

Yogev, 2004 97 0 (0, 0.076)
 

Ravasia, 2000 (poor) 172 0.029 (0.012, 0.068)
 

Lydon-Rochelle, 2001 366 0.025 (0.013, 0.047)
 

Overall 690 0.024 (0.014, 0.039)
 

Cohort, term studies 

Zelop, 1999 102 0.039 (0.015, 0.100) 

Grobman, 2007 754 0.008 (0.004, 0.018) 

Overall 856 0.017 (0.004, 0.080) 

0.020 (0.011, 0.035) (Total) overall 

0.001	 0.01 0.1 1.0 

Uterine rupture rate (95% confidence interval) 

*95% confidence intervals are exact

Dose of PGE2 was sporadically reported, and when reported was not consistent in the 

reporting metric (e.g., mean number of doses versus the number of women receiving two or three 

doses). Similarly, while the number of prior cesarean delivery and the rate of prior vaginal 

deliveries may have influenced the rate of VBAC with PGE2 induction, these covariates were not 

reported adequately for analysis. A small number of studies did report these variables, but either 

did not stratify the results by specific induction method,156 or had too few numbers to allow 

analysis.157 

Misoprostol. Evidence for maternal harms with misoprostol is limited to three fair quality 

cohort studies, including women with any GA.11, 172, 211 The largest of these,11 used ICD-9 codes 

to identify uterine ruptures, a procedure now known to overestimate rupture rates. Additionally, 

although the study is large (N=20,525), only 366 received prostaglandins of any kind. The data 

were collected between 1987 and 1996, and it is noted that misoprostol was not used regularly 

62 
until 1996, indicating that few of the women described as receiving a prostaglandin had 

misoprostol. While the actual numbers of women receiving misoprostol are not reported, the 

relative risk for a uterine rupture in women who received a prostaglandin during 1996 was 12.2 

(95 percent CI: 3.4 to 39.6). This compares with a separate analysis of uterine rupture among 

women who received a prostaglandin during the years 1987 to 1995, relative risk 14.1 (95 

percent CI: 6.1 to 33.0; both compared with ERCD). 

The other two studies are much smaller, but do report misoprostol data separately. In a small, 

fair quality, cohort study (N=226) comparing PGE2 (administered as a gel or pessary) with 

misoprostol (25 to 50 mcg),211 only 16 of 145 women in the misoprostol group and nine of 81 in 

the PGE2 group had a prior cesarean delivery. Additionally, the data for PGE2 was obtained 

retrospectively while the data for misoprostol were obtained prospectively. The results for 

uterine rupture were stratified by history of a prior cesarean delivery with two of 16 in the 

misoprostol group (13 percent) and zero of nine in the PGE2 group having what is described only 

as a low transverse rupture. One additional patient in the misoprostol group had a scar 

dehiscence. In both cases of rupture, hysterectomy was performed, with no blood transfusions. 

The second study of misoprostol made comparisons among women with a history of prior 

cesarean delivery to those without prior cesarean delivery, a comparison that is not relevant to 

this review.172 There were no uterine ruptures, and 2.0 percent were reported as having 

“complications,” including abruption placenta, retained placenta, uterine atony, and blood 

transfusion. 

Mifepristone. In a small (N=32), fair quality trial of mifepristone and placebo, each given for 

2 days followed 2 days later by IOL with prostaglandins, oxytocin, and/or artificial rupture of 

membranes as needed in term GAs,173 one uterine scar separation occurred in each group (6.25 

percent). Maternal outcomes were not different between groups, except that two patients in the 

mifepristone group developed fever, compared with none in the placebo group. One wound 

infection was found in each group. 

Oxytocin. The risk of uterine rupture following induction or augmentation of labor with 

oxytocin was reported as a main outcome measure in eight studies (one good quality cohort 

study, four fair quality cohort studies, and three fair quality case series).11, 125, 156-158, 164, 168, 169 

The risk of uterine rupture is 1.1 percent (95 percent CI: 0.9 to 1.5 percent) when data from these 

studies are pooled (Figure 17). 

63 
 

 

 

 

 

 

 

 

 

Figure 17. Uterine rupture with oxytocin 

Grobman, 2007 

(term cohort study) 

Zelop, 1999 

(term cohort study) 

Flamm, 1987 

(any GA cohort study) 

Lydon-Rochelle, 2001 

(any GA cohort study) 

Ravasia, 2000 

(any GA cohort study) 

Kayani, 2005 

(any GA case series study) 

Locatelli, 2006 

(any GA case series study) 

Meehan, 1989 

(any GA case series study) 

Overall 

2,421 

458 

149 

1,960 

274 

45 

124 

162 

Study Name N Uterine Rupture Rate 

(95% Confidence Interval)* 

0.012 (0.008, 0.017) 

0.020 (0.010, 0.037) 

0.013 (0.003, 0.052) 

0.008 (0.005, 0.013) 

0.007 (0.002, 0.029) 

0.022 (0.003, 0.142) 

0 (0, 0.061) 

0.006 (0.001, 0.042) 

0.011 (0.009, 0.015) 

0.000 0.005 0.010 0.015 0.020 0.025 

Uterine rupture rate (95% confidence interval) 

*95% confidence intervals are exact 

Abbreviation: GA= gestational age 

A case control study of 24 cases of uterine rupture where oxytocin had been given during 

TOL after prior cesarean delivery and 96 controls that also received oxytocin but had no uterine 

rupture examined the relationship of oxytocin dose to rupture.174 The study was powered to find 

a difference of 40 percent in the duration of oxytocin or a 65 percent increase in total dose. None 

of the multiple analyses found a statistically significant difference, although the difference in 

duration of oxytocin (530 minutes in the uterine rupture group compared with 476 in the nonrupture group) achieved a p value of 0.08. The study was small, and the large differences of 40 

percent for duration and 65 percent for dose appear to have been set arbitrarily. Further analysis 

of the impact of dose on uterine rupture rate may be warranted. 

Oxytocin augmentation of labor. Augmentation of labor with oxytocin may be an important 

confounder for uterine rupture; among the 12 studies reporting uterine rupture as a main outcome 

measure, eight reported the proportion of women receiving augmentation of labor ranging from 

16 to 81 percent (Table 9).145, 148, 149, 151, 156-158, 168 Meta-regression of these data did not result in 

oxytocin augmentation to be a statistically significant covariate for uterine rupture with PGE2 

induction (p=0.22). While this evidence may be too limited to make conclusions about an 

association between proportions of women having both PGE2 induction and oxytocin 

64 
 

augmentation of labor and increasing uterine rupture rates, there is at least a trend towards 

increased risk when both drugs are used. 

Table 9. Effect of oxytocin augmentation on rate of uterine rupture in women receiving 

prostaglandin E2 for induction 

Study, year Study design GA 

N 

induced 

with PGE2 

% Uterine 

rupture 

% 

Augmented 

with 

oxytocin 

Grobman, 

2007156 

Cohort 

MFMU 

Term 754 0.8 0.81 

Yogev, 2004145 Cohort 

women with 1 prior CD with 

IOL 

Any 

GA 

97 0 0.25 

Ben-Aroya, 

2002148 

Cohort 

University hospital 

women in 2nd delivery, 

following a CD 

Any 

GA 

55 0 0.16 

Meehan, 1989158 Case series 

University teaching hospital 

women with 1 prior CD, 

nominated for TOL 

Any 

GA 

52 1.9 0.44 

Locatelli, 2006168 Case series 

University hospital 

women with a previous CD 

Any 

GA 

310 0.3 0.4 

Kayani, 2005157 Case series 

Larger inner city teaching 

hospital women with IOL 

after 1 prior CD 

Any 

GA 

149 0.7 0.35 

Chilaka, 2004151 Case series 

University hospital 

women with prior CD, who 

had IOL 

Any 

GA 

130 0 0.27 

Blanco, 1992149 Case series 

University hospital 

women attempting TOL 

Any 

GA 

25 0 0.2 

Abbreviations: CD=cesarean delivery; GA=gestational age; IOL=induction of labor; MFMU=MaternalFetal Medicine Units Network; PGE2=prostaglandin E2; TOL=trial of labor 

Prostaglandin E2 versus oxytocin. The best evidence on the risk of uterine rupture with PGE2 

compared with oxytocin when used for IOL comes from a large good quality cohort study of 

women with term gestations and one prior cesarean delivery.156 In this study there were no 

uterine ruptures in the prostaglandin only group, 29 out of 2,421 (1.2 percent) in the oxytocin 

only group, and six out of 614 in the prostaglandin plus oxytocin group (1 percent). Statistical 

comparisons were made only with the spontaneous labor group and stratified by prior vaginal 

delivery or no prior vaginal delivery. The group with no prior vaginal delivery and receiving 

oxytocin only resulted in a statistically significantly greater risk of uterine rupture (odds ratio 

2.19; 95 percent CI: 1.28 to 3.76). Analysis of the other groups compared with spontaneous 

labor, including PGE2 only, did not result in significantly increased risk. A second, lower quality 

cohort study similarly found the risk of uterine rupture to be significantly increased with 

oxytocin induction (odds ratio 4.6; 95 percent CI: 1.5 to 14.1) but not with PGE2.

164 The pooled 

analysis of these results in an odds ratio of 2.7 (95 percent CI: 1.4 to 5.1) compared with 

65 
 

spontaneous labor. Direct comparisons are not available, and the number of women in the 

prostaglandin only groups is much smaller than in the oxytocin only groups. Using the data 

presented in the large cohort study for uterine rupture in the oxytocin only group (prior and no 

prior vaginal delivery combined) compared with prostaglandin only (prior and no prior vaginal 

delivery combined) yielded an unadjusted odds ratio of 0.29 (95 percent CI: 0.04 to 2.09) 

indicating no statistically significant difference in risk. However, this is an exploratory analysis 

and should be interpreted with caution. 

Mechanical methods of induction. The evidence on the risk or benefits of mechanical 

methods of cervical ripening in women with a prior cesarean delivery is very limited.148, 150, 169, 

179, 180 The best of these are two small retrospective cohort studies evaluating the use of a foley 

catheter for cervical ripening compared to spontaneous labor.148, 150 No cases of uterine rupture 

occurred in the groups who had foley catheter cervical ripening, although the numbers of patients 

in the foley catheter groups may have been too small to identify a rupture (N=416). Additionally, 

while one study was rated good quality and defined uterine rupture clearly, it is not clear that 

evidence of uterine rupture was routinely sought in all women,150 and the other study provided 

no definition for uterine rupture.148 

Any induction method. The risk of uterine rupture associated with a TOL and IOL using any 

method was assessed using 14 fair quality studies, involving 12,659 women.11, 60, 96, 121, 125, 150, 154, 

156-158, 160, 164, 167, 169 Combining these data results in a risk of 1.2 percent (95 percent CI: 0.9 to 1.6 

percent) as shown below, with one small study reporting no uterine ruptures (0 percent) (Figure 

18). 

66 
 

 

 

 

 

 

 

 

 

 

Figure 18. Risk of uterine rupture with any induction method 

Study Name N Uterine Rupture Rate (95% 

Confidence Interval)* 

Gibson, 1988 (term cohort study) 10 0 (0, 0.448) 

Grobman, 2007 (term cohort study) 3,259 0.011 (0.008, 0.015) 

Zelop, 1999 (term cohort study) 290 0.021 (0.009, 0.045) 

Bujold, 2004 (any GA cohort study) 672 0.013 (0.007, 0.026) 

Delaney, 2003 (any GA cohort study) 803 0.007 (0.003, 0.017) 

Flamm, 1987 (any GA cohort study) 485 0.004 (0.001, 0.016) 

Flamm, 1997 (any GA cohort study) 453 0.013 (0.006, 0.029) 

Hammoud, 2004 (Any GA cohort study) 685 0.015 (0.008, 0.027) 

Locatelli, 2004 (any GA cohort study) 310 0.003 (0, 0.023) 

Lydon-Rochelle, 2001 (any GA cohort study) 2,326 0.010 (0.007, 0.015) 

Rageth, 1999 (any GA cohort study) 2,459 0.007 (0.004, 0.011) 

Ravasia, 2000 (any GA cohort study) 575 0.026 (0.016, 0.043) 

Kayani, 2005 (any GA case series study) 205 0.020 (0.007, 0.051) 

Meehan, 1989 (any GA case series study) 127 0.008 (0.001, 0.054) 

Overall 0.012 (0.009, 0.016) 

0.0 0.2 

Uterine rupture rate (95% confidence interval) 

*95% confidence intervals are exact
 

Abbreviation: GA= gestational age
 

Unfortunately, studies that reported the proportion of women with induced or augmented 

labors reported other maternal outcomes too infrequently to be meaningfully assessed. 

Amnioinfusion. One small cohort study of women with prior cesarean delivery compared the 

rate of uterine rupture, defined as “full thickness separation of scar requiring operative 

intervention”, in women who underwent amnioinfusion during labor and those who did not.138 

However, exploration of the uterus was only undertaken among those with VBAC. The total 

number of women studied was1,436, with 122 having received amnioinfusion. The rate of 

rupture was 0.8 percent in the amnioinfusion group and 1.1 percent in the group without 

amnioinfusion. There was no statistically significant difference in the rate of rupture between the 

groups, RR 0.72 (0.10 to 5.39). A smaller study reported no ruptures, but the definition and 

ascertainment of rupture was unclear.212 

Summary and strength of the evidence on effect of induction of labor on uterine rupture. The 

strength of evidence on the risk of uterine rupture with pharmacologic IOL methods was low due 

to lack of precision in estimates and inconsistency in findings. The overall risk of rupture with 

any IOL method at term was 1.5 percent and 1.0 percent when any GA is considered. Among 

women with GA greater than 40 weeks, the rate was highest at 3.2 percent. Evaluation of the 

evidence on specific methods of IOL reveal that the lowest rate occurs with oxytocin at 1.1 

percent, then PGE2 at 2 percent, and the highest rate with misoprostol at 6 percent. These 

67 
findings should be interpreted with caution as there was imprecision and inconsistency in the 

results among these studies. The risk of uterine rupture with mechanical methods of IOL is 

understudied. Other harms were inadequately reported to make conclusions. Relative to women 

with spontaneous labor, there was no increase in risk of rupture among those induced at term. 

However, the available evidence on women with induced labor after 40 weeks GA indicates an 

increased risk compared with spontaneous labor (risk difference 1.8 percent; 95 percent CI: 0.1 

to 3.5 percent). The NNH in this group is 56 (for every 56 women greater than 40 weeks GA 

with IOL during a TOL, one additional rupture will occur compared with having spontaneous 

labor). 

Individual factors associated with uterine rupture. The impact of individual factors on 

uterine rupture can overlap and interact with each other such that a factor found to have 

statistically significant influence may no longer be significant when other key factors are taken 

into account. Studies that evaluate these factors in concert, using regression analyses for 

example, can provide a higher level of evidence on the residual influence of individual factors. 

Table 10 presents odds ratios reported by 11 good or fair quality studies that examined the 

relationship between individual factors and uterine rupture using the anatomic definition for 

uterine rupture.60, 80, 119, 150, 213-219 Individual factors associated with uterine rupture were grouped 

into four general categories: 1) demographic, 2) past obstetric factors, and 3) current obstetric 

factors. Nonclinical factors such as hospital type, VBAC volume, hospital delivery volume, 

maternal substance use or maternal medical conditions were only presented in studies that did 

not use the anatomical definition for uterine rupture or did not present a definition of uterine 

rupture and are therefore left off the table. 

Table 10. The odds of uterine rupture after cesarean delivery by factor 

Studies using 

anatomical uterine 

rupture definition 

Adjusted odds ratio for uterine 

rupture† 

(95% CI or p value) 

Demographic 

Maternal Age 

Bujold, 2002214

Shipp 2003*218 

Shipp 2008*219 

 0.95 (> 35y): (0.31-2.92) 

13.78 (>30y): (1.56-122.05) 

2.6 (30-39 y): (1.1-6.0) 

5.8 (> 40y): (1.6-20.3) 

Past obstetric factors 

Prior vaginal delivery 

Grobman,2008*215

Shipp, 2008219

Bujold 2002213

Caughey, 1999119

Landon, 2006*80

 0.44: (0.27-0.71) 

 0.3: (0.1-0.9) 

 0.42: (0.05-3.17) 

 0.26: (0.08-0.88) 

 0.62: (0.43-0.82) 

Current obstetric factors 

Prior vaginal birth after 

cesarean 

Landon, 200680 0.52: (0.34-0.82) 

Number of prior cesarean 

deliveries 

Caughey, 1999119 

Landon, 200680 

4.8 (2 versus 1): (1.8-13.2) 

1.36 (multiple): (0.69-2.69) 

68 
Table 10. The odds of uterine rupture after cesarean delivery by factor 

Studies using 

anatomical uterine 

rupture definition 

Adjusted odds ratio for uterine 

rupture† 

(95% CI or p value) 

Shipp, 2008219 5.3 (2 or more): (2.1-12.9) 

Gestational age Hammoud, 200460

Sciscione, 2008217 

Shipp, 2003218 

 2.8 (>41 versus 37-40): (1.27-6.42) 

2.05 (preterm versus term with 

ERCD): (1.39-2.55) 

1.73 (preterm versus term excl 

ERCD): (1.17-2.55) 

0.24 (>40wks): (0.04-1.43) 

Birth weight Bujold, 2002214

Bujold, 2002213 

Landon, 200680

Shipp,2003218

 1.02(>3500g): (0.42-2.47) 

2.10 (>4,000g): (0.76-5.88) 

 1.09 (> 4,000g): (0.60-1.97) 

 2.26 (> 4,000g): (0.47-10.82) 

Inter-delivery interval Bujold, 2002*214

Bujold, 2002*213

Landon, 200680

Shipp, 2008219 

 2.65 (<24 mos): (1.08-5.46) 

 2.31 (<24 mos): (0.97-5.52) 

 2.05 (<24 mos): (1.41-2.96) 

2.4 (<18 mos): (1.0-5.6) 

Induction Bujold, 2002214

Bujold, 2004150 

Grobman,2007*220

Kieser, 2002216 

 1.82: (0.66-5.04) 

0.75(use of oxytoxcin): (0.26-2.21) 

1.81 (foley): (0.59-5.56) 

0.47 (foley): (0.06-3.59) 

 1.39: (0.62-3.13) 

0.71: (0.12-3.81) 

0.53 (oxytocin): (0.04-4.38) 

0.56 (PG): (0.01-11.81) 

Landon, 2004*221 2.86: (1.49-3.93) 

3.01 (oxytocin alone): (1.66-5.46) 

3.95 (PG +oxytocin): (2.01-7.79) 

Landon, 2006*80 1.78: (1.24-2.56) 

Augmentation Landon, 200680 2.41: (1.49-3.93) 

Epidural Bujold, 2002*214 1.83: (0.50-6.67) 

69 
Table 10. The odds of uterine rupture after cesarean delivery by factor 

Studies using 

anatomical uterine 

rupture definition 

Adjusted odds ratio for uterine 

rupture† 

(95% CI or p value) 

Bujold, 2002*213 2.10: (0.76-5.84) 

Landon, 200680 1.76: (1.13-2.75) 

Layers of closure Bujold, 2002*214 4.33 (single): (1.70-10.98) 

Bujold, 2002*213 3.95 (single): (1.35-11.49) 

* Uses same data source 

†

Odds ratio considered significant if confidence interval does not include 1.0 or p<0.05 

Abbreviations: CI=confidence interval; ERCD=elective repeat cesarean delivery; g=grams; mos=months; 

PG=prostaglandin; VBAC=vaginal birth after cesarean; wks=weeks; y=year(s) 

As shown, prior vaginal delivery and prior VBAC consistently appear to significantly reduce 

the risk of uterine rupture with odds ratios of 0.26 to 0.62 for prior vaginal delivery and 0.52 for 

prior VBAC. Inter-delivery interval less than 18 to 24 months and single layer closure appear to 

increase risk of uterine rupture with odds ratios of 2.05 to 2.65, and 3.95 to 4.33, respectively. 

However, caution should be used in interpreting the finding for layers of closure as this is based 

upon one study and the same study reports an increased risk for uterine rupture among preterm 

births, which is contrary to the reports of TOL and ERCD cohort studies. 

Use of imaging to predict uterine rupture. The evidence on the use of various imaging 

modalities such as ultrasound, X-ray pelvimetry and endoscopy to predict uterine rupture risk is 

limited and consists of four fair quality cohort studies and six poor quality case series.82, 83, 222-229 

The best evidence comes from three fair quality prospective cohort studies that measured full 

thickness lower uterine segment using ultrasound measurements between 35 and 38 6/7 weeks 

gestation.82, 83, 223 The first study conducted in France from 1989 to 199483 provides the most 

robust study design of the three to test the value of ultrasound as neither women nor their 

clinicians were informed of the results prior to delivery, thus removing the potential bias that 

could result from clinicians directing their patients towards or away from VBAC due to imaging 

results. In this study, women underwent ultrasound measurements of the lower uterine segment 

using a standardized method between 36 and 38 weeks and patients were divided into four 

groups according to full lower uterine segment thickness greater than 4.5 millimeters (mm), 3.6 

to 4.5mm, 2.6 to 3.5mm and 1.6 to 2.5mm. There was a significant association between uterine 

wall thinning and uterine scar defects, defined as uterine rupture or dehiscence. Overall, the 

relative risk of a defect was 20.1 percent (95 percent CI: 8.3 to 48.9 percent) for lower uterine 

segment less than or equal to 3.5mm and 6.3 percent (95 percent CI: 2.8 to 13.9 percent) for 

measurements less than or equal to 2.5mm. While measurements greater than 4.5mm had a 

negative predictive value of 100 percent given no cases of defect in this group, the positive 

predictive value for a thickness less than 3.5mm was not good at 11.8 percent (negative 

predictive value 99.3 percent). Of note, this population included women with multiple prior 

cesarean deliveries and there was no clear association between number of prior cesareans and 

uterine thickness measurements. This study did not adjust for other factors that might also 

contribute to risk such as direction of prior cesarean scar, estimated fetal weight, co-morbidities, 

indication for prior cesarean delivery, history of prior vaginal delivery etc. While the two 

additional studies that follow, Rozenberg 199982 and Bujold 2009,223 have higher risk of bias as 

70 
clinicians were informed of the imaging results prior to delivery, both support the association 

between uterine thickness and uterine rupture (Table 11). 

Table 11. Lower uterine segment thickness and uterine defect 

Author, 

year 

Study 

years/Population 

LUS Thickness (mm) and 

Uterine Defect Additional Results 

Rozenberg, Prospective Cohort 1.6-2.5mm – 8/51 (16%) Cut off 3.5mm 

199683 1989-1994 2.6-3.5mm 14/136 (10%) Sensitivity 88% 

Single University 3.6-4.5mm – 3/177 (2%) Specificity 73.2% 

hospital 4.5mm – 0/278 (0%) PPV 11.8% 

Paris, France NPV 99.3% 

Bujold, Prospective Cohort < 2.0mm – 4/35 (11%) Single layer closure & inter2009223 2004-2006 

Single University 

institution Montreal 

Canada 

2.0-2.4 – 2/52 (3.8%) 

2.5-2.9 – 1/40 (2.5%) 

3.0-3.4 – 1/50 (2%) 

>3.5 - 1/59 (1.7%) 

delivery interval <24 

months associated with 

defect (not rupture) 

In TOL group LUS 

thickness of <2.3mm & UR 

results in 

Sensitivity 100% 

Specificity 75% 

9.1% UR in TOL 

Abbreviations: LUS=lower uterine segment; mm=millimeter; NPV=negative predictive value; PPV=positive 

predictive value; TOL=trial of labor; UR=uterine rupture 

Strength of evidence for individual factors as predictors of uterine rupture. Studies of 

individual factors that may increase or decrease a woman’s risk of uterine rupture are largely 

exploratory, as few factors have been confirmed in prospective studies as suggested by Simon 

and Altman, 1994.193 There is cross validating evidence to suggest that women with prior vaginal 

delivery have lower risk for uterine rupture and women undergoing IOL have higher risk of 

uterine rupture compared with spontaneously laboring women. Similarly, evidence from IOL 

studies suggest that women who are postdates may have a higher risk of uterine rupture. The 

evidence on the role of imaging to predict uterine rupture is low due to limited studies with highrisk for bias; however, the existing data suggest that there may be value to ultrasound 

measurements of uterine thickness for women with prior cesarean delivery. 

Predictive models for uterine rupture. Because uterine rupture is such an important 

consideration for women with prior cesarean delivery, several investigators have attempted to 

build predictive tools that would combine the individual predictors to estimate a woman’s risk 

for uterine rupture. Four studies attempted to develop predictive models for uterine rupture (see 

Appendix P for study details).104, 215, 219, 230 Only two tested their predictive model in a validation 

group.104, 215 No study was able to produce a reliable and robust model to predict uterine rupture. 

Signs of uterine rupture and management to reduce uterine rupture related mortality. 

Given the serious potential consequences for morbidity and mortality given uterine rupture, it 

would be ideal to understand signs and symptoms of uterine rupture and what, if any 

interventions might reduce the likelihood of morbidity or mortality in the event that a uterine 

rupture does occur. As stated in a prior VBAC evidence report, and echoed in studies contained 

in this report, there is no single sign for the occurrence of uterine rupture; however, fetal heart 

tracing abnormalities, particularly fetal bradycardia (reported in 33 to 100 percent of all studies) 

is the most frequently reported sign of uterine rupture.62, 206-208 Other signs reported in uterine 

rupture studies in descending order are maternal vaginal bleeding, maternal pain, and uterine 

contraction disturbances. 62 

71 
The next important question is whether there are any management or system factors that 

might reduce the likelihood for an adverse outcome in the event of uterine rupture. Two fair 

quality case series231, 232 have specifically studied whether time from signal of uterine rupture to 

delivery predicts perinatal outcomes. Leung et al were the first to perform an exploratory 

analysis to study risk factors for poor neonatal and maternal outcome; particularly fetal heart rate 

(FHR) and uterine contraction patterns.233 They identified 106 cases of symptomatic uterine 

rupture from 11,179 TOLs in women with prior cesarean delivery at Los Angeles County 

University of Southern California Women’s Hospital, from which they were able to review 99 

records. The scar type was unknown in 99 percent of their population. They categorized cases of 

uterine rupture based on complete, partial, or no extrusion of the fetus. Combining death, 

asphyxia, and respiratory distress, they concluded that perinatal morbidity and mortality was 

significantly greater in cases where the fetus was extruded. Looking for premonitory signs of 

uterine rupture, they found that prolonged decelerations occurred in 17/41 (41.5 percent) patients 

with extrusion and 15/58 (25.9 percent) without and that no patient who had prolonged 

deceleration only as their sign of rupture had significant clinical morbidity when delivery 

occurred within 17 minutes of the onset of deceleration. Four of six infants (67 percent) who 

died due to uterine rupture presented to labor and delivery in “fetal distress” and two of six 

occurred in women undergoing TOL. It is important to note that 57 percent of uterine ruptures 

with fetal extrusions occurred in women with two or more prior cesarean deliveries; 21 percent 

in classical or vertical incisions, 21 percent in unknown incisional type, and 58 percent in LTCD. 

A second case series of 23 uterine ruptures out of Canada found no relation between time 

from FHR deceleration and infant outcome.231 As above, the study was conducted in a tertiary 

care hospital with in-house anesthesia and obstetrics. Fetal heart rate abnormalities—which 

included tachycardia and late, variable, or prolonged (not defined) decelerations—were the 

initial sign of uterine rupture in 20/23 (87 percent) of cases (four had pain, one vaginal bleeding, 

and one hematuria). Prolonged deceleration was the first sign of uterine rupture in 6/6 (100 

percent) of the extruded patients versus 8/17 (47 percent) without extrusion. There was one 

perinatal death that occurred in the non-extruded group (late decelerations more than 25 minutes 

before delivery, failed vacuum extraction, then cesarean delivery), and three cases of impaired 

motor development diagnosed as hypoxic-ischemic encephalopathy (HIE), occurring in the 

extruded group; delivery occurred 15, 16, and 23 minutes from onset of prolonged deceleration. 

When they looked at metabolic acidosis (their primary outcome, defined as umbilical artery pH 

less than 7.0 with base deficit greater than 12mMol/L), they found a non-significant trend 

towards less time between first sign to delivery (18 versus 24 minutes) and decision to delivery 

(13 versus 17 minutes) in the group with metabolic acidosis compared with those without 

acidosis (p=0.11). In this case, the greater time delays in the group without metabolic acidosis 

could reflect less concern by the physician and thus a slower overall movement, rather than 

programmatic delays. 

Summary and strength of the evidence on uterine rupture. Overall, the literature relating 

to response time between premonitory signs of uterine rupture and perinatal mortality are 

insufficient. This is due to study designs that are more prone to bias, inconsistent findings, 

imprecision and difficulty accounting for time among women who presented with concerning 

fetal tracings (e.g. whether the patient had concerning tracing at arrival to the hospital). 

However, there is suggestion that fetal bradycardia is an ominous sign for fetal extrusion, which 

is associated with poor perinatal outcomes, and prompt delivery in this setting is warranted. 

72 
Hysterectomy 

Overall there were 16 cohort studies reporting hysterectomy as a complication of ERCD, 

VBAC, and RCD after a TOL;10, 77, 78, 80, 81, 93, 100, 108, 137, 164, 201, 204, 228, 234-236 eight provided 

information comparing risks for hysterectomy between TOL and ERCD (Table 12).10, 77, 81, 93, 108, 

201, 204, 234 As shown in Figures 19 and 20, while the occurrence of hysterectomy was higher for 

ERCD at 0.28 percent (95 percent CI: 0.12 percent to 0.67 percent) compared to 0.17 percent (95 

percent CI: 0.12 to 0.26 percent) for TOL but the difference was not statistically significant. 

Three of the eight studies focused exclusively on women delivering at term.93, 108, 204 Among 

these studies, the combined risk of hysterectomy was 0.14 percent (95 percent CI: 0.08 to 0.22 

percent) in the TOL group and 0.16 percent (95 percent CI: 0.07 to 0.36 percent) in the ERCD 

group. The risk was not significantly different between the two groups (p=0.672). Among the 

five studies including women delivering at any gestational age, the combined risk of 

hysterectomy was 0.22 percent (95 percent CI: 0.13 to 0.38 percent) for TOL and 0.43 percent 

(95 percent CI: 0.11 to 0.17 percent) for ERCD. Compared with ERCD, TOL had a significantly 

lower risk of hysterectomy (RR, 0.40; 95 percent CI: 0.18 to 0.92, p=0.03). Using 0.43 percent 

as the baseline risk for ERCD, the calculated risk difference was -0.26 percent (95 percent CI: ­

0.35 to -0.04 percent), translating to 2.6 fewer hysterectomies per 1,000 for TOL. 

There was significant heterogeneity among the studies. In particular, Phelan and Eglinton 

appeared to be outliers for ERCD among term studies and because of its size, Wen is exerting 

significant effect on all analyses and particularly for ERCD; this study has a low occurrence of 

hysterectomy. Studies were explored for factors that might explain the observed heterogeneity. 

Considered factors included setting (university versus community), gestational age, number, and 

direction of scar, and no clear pattern was observed across the eight studies. 

Individual studies looked for factors that may affect the occurrence of hysterectomy among 

women with prior cesarean. In particular, several publications from the MFMU study, report 

interesting potential contributors. Grobman et al examined the influence of induction of labor 

and reported that induction was associated with almost a 4-fold increase in the occurrence of 

hysterectomy (odds ratio 3.92; 95 percent CI: 1.10 to 13.9) among women without a history of 

prior vaginal delivery. Mercer et al evaluated the risk of hysterectomy with increasing number of 

VBACs found a non-significant decrease in the rate of hysterectomy from 0.23 percent with no 

prior VBAC to 0.016 percent in subjects with two or more previous VBACs (p=0.15).192 Perhaps 

the most intriguing factors reported from this group is in regards to the influence of multiple 

prior cesarean deliveries and prior vaginal delivery. In subjects undergoing multiple cesarean 

deliveries, there was a decrease in hysterectomy rate between the first and second cesarean 

delivery, followed by an increase from 0.42 percent after two cesarean deliveries to 9.0 percent 

after six or more previous cesarean deliveries.236 Only one study evaluating this cohort compared 

hysterectomy rate among VBAC after one cesarean delivery, VBAC after greater than one 

cesarean delivery, and ERCD. This study found the lowest proportion of hysterectomy among 

those with VBAC after a single cesarean delivery (0.2 percent), intermediate levels after ERCD 

(0.4 percent), and the highest among those with VBAC after multiple previous cesarean 

deliveries (0.6 percent).80 These two studies suggest multiple cesarean deliveries increase risk for 

hysterectomy at the time of delivery; VBAC may be protective against hysterectomy after 

multiple cesarean deliveries. However, this comparison is limited by a lack of information about 

the actual number of previous cesarean deliveries and TOL in the latter article, and therefore a 

dose–dependent effect of increasing number of cesarean deliveries with TOL and VBAC cannot 

be determined. Furthermore, the inclusion criteria for ERCD limited its applicability, as only low 

73 
risk ERCD candidates were included. Using data from a California state database, Gregory et al 

found that underlying medical and obstetrical risk may increase a woman’s chance for 

hysterectomy reporting a two-fold increase in hysterectomy for ERCD compared with TOL 

among women with high-risk pregnancies (0.41 versus 0.22 percent).93 

74 
Table 12. Hysterectomy for trial of labor versus elective repeat cesarean delivery 

Author, Year Study description N Hysterectomy proportion P

Term Gregory,20089 3 Retrospective cohort Low-risk = absence of maternal 

complications High-risk = any maternal condition ICD9 codes 

41,450 Hysterectomy (rates) 

Low-risk TOL: 9/8,292 (0.10%) ERCD: 21/20,834 (0.10%) High-risk TOL: 7/3,188 (0.22%) ERCD: 38/9,136 (0.41%) 

LTRHTR

Spong, 2007204 

MFMU Cohort 19 university hospitals 

39,117 TOL 31/15,323 (0.2%) 

ERCD (no labor): 40/14,993 (0.27%) ERCD (labor): 9/2,721 (0.33%) IRCD (no labor): 43/5,002 (0.86%) IRCD (labor): 3/1,078 (0.28%) 

TEEII

Wen,2004108 Retrospective cohort 

Canadian Registry ICD9 codes 

308,755 TOL: 127/128,960 (0.10%) 

RCD: 140/179,795 (0.08%), Adjusted odds ratio 1.26 (0.99-1.61) 

TR

Any gestational age Eglinton,19842 01 Retrospective cohort University Hospital 871 TOL:1/376 0.3% RCD: 6/495 1.2% T

R

Flamm, 199477 Prospective cohort 

10 Kaiser Hospital in CA 

7,229 TOL: 6/5,022 (0.12%) 

RCD: 6/2,208 (0.27%) p= Not significant 

TR

Hibbard, 2001234 Prospective Cohort University Hospital 2,450 TOL: 6/1,324 (0.5%) VBAC: 4/908 (0.44%) TOL-CD: 2/416 (0.93%) 

RCD: 0/431 (0%) 

TV TR

McMahon,199 610 Retrospective cohort Population based 

Longitudinal study 

6,138 TOL: 5/3429 (0.15%) 

RCD: 6/2,889 (0.2%) 

TR

Phelan, 198781 Prospective Cohort University hospital 

>2 prior CD only 

2,643 TOL: 5/1796 (0.3%) 

RCD: 14/847 (1.7%) 

TR

Abbreviations: CA=California; CD=cesarean delivery; ERCD=elective repeat cesarean delivery; IRCD=indicated repeat cesMFMU=Maternal-Fetal Medicine Units Network; RCD=repeat cesarean delivery; TOL=trial of labor; TOL-CD=trial of labor f

delivery; VBAC=vaginal birth after cesarean 
 

 

 

(95%Confidence Interval) 

Overall(I-squared = 75.4%, p < 0.001) 

Gregory, 2008 

Any gestational age 

Combined (I-squared = 38.9%, p = 0.162) 

Flamm,1994 

Phelan,1987 

Eglinton,1984 

Spong, 2007 

Wen, 2004 

Combined (I-squared = 85.2%, p = 0.001) 

Hibbard, 2001 

McMahon, 1996 

Term only 

11480 

5022 

1796 

376 

15323 

128960 

1324 

3429 

16 

6 

5 

1 

31 

127 

6 

5 

0.0017 (0.0012, 0.0026) 

0.0014 (0.0008, 0.0023) 

0.0022 (0.0013, 0.0038) 

0.0012 (0.0004, 0.0026) 

0.0028 (0.0009, 0.0065) 

0.0027 (0.00007,0.0147) 

0.0020 (0.0014, 0.0029) 

0.0010 (0.0008, 0.0012) 

0.0014 (0.0008, 0.0022) 

0.0045 (0.0017, 0.0098) 

0.0015 (0.0005, 0.0034) 

0 .005 .01 .015 .02 

Figure 19. Hysterectomy occurrence for trial of labor 

Hysterectomy Rates Study Total Event 

76 
 

 

 

 

 

Figure 20. Hysterectomy occurrence for elective repeat cesarean delivery 

Study Total Event Hysterectomy Rates 

(95%Confidence Interval) 

Term only 

Wen,2004 179795 140 0.0008 (0.0007, 0.0009) 

Spong, 2007 17714 49 0.0028 (0.0020, 0.0037) 

Gregory, 2008 29970 59 0.0020 (0.0015, 0.0025) 

Combined (I-squared = 97.3%, p < 0.001) 0.0016 (0.0007, 0.0036) 

Any gestational age 

Eglinton,1984 495 6 0.0121 (0.0045, 0.0262) 

Phelan,1987 847 14 0.0165 (0.0091, 0.0276) 

Flamm,1994 2208 6 0.0027 (0.0010, 0.0059) 

McMahon, 1996 2889 6 0.0021 (0.0008, 0.0045) 

Hibbard, 2001 431 0 0 (0, 0.0085) 

Combined (Test of heterogeneitybased on 0.0043 (0.0011, 0.0170) 

Fisher’s exacttest: p < 0.001.) 

Overall(Test of heterogeneitybased on 0.0028 (0.0012, 0.0067) 

Fisher’s exacttest: p < 0.001.) 

0 .005 .01 .015 .02 .025 .03 

Summary of hysterectomy. Hysterectomy is rare with either ERCD or TOL, occurring in 

less than 3 percent of deliveries for women with a prior cesarean delivery. There was no 

significant difference in the occurrence of hysterectomy based upon route of delivery overall or 

among women delivering at term; however there was a lower occurrence of hysterectomy among 

women undergoing a TOL among studies enrolling women of any gestational age. 

Transfusion/Hemorrhage 

Transfusion. Nine cohort studies of good or fair quality totaling 401,307 patients evaluated 

the occurrence of transfusion between ERCD and TOL10, 76, 77, 93, 95, 97, 108, 204, 234 (see Appendix Q 

for a detailed description of studies). As shown in Figure 21, the occurrence of transfusion was 

not significantly different between TOL and ERCD (0.9 versus 1.2 percent, this translates to nine 

versus 12 per 1,000). There was significant heterogeneity among the studies however with 

studies varying widely on the frequency of transfusion, with transfusion rates ranging from 0.5 to 

4.3 percent for TOL and 0.1 to 5.5 percent for ERCD. Studies were also conflicting on which 

group had the highest rate of transfusion with five studies reporting greater transfusions with 

ERCD,10, 76, 77, 95, 234 and four reporting greater transfusions in TOL.93, 97, 108, 204 The studies were 

examined for potential factors that may explain the difference. Factors that were reported among 

studies included gestational age, accuracy of group assignment, maternal conditions particularly 

underlying high-risk medical conditions, hospital setting, and the influence of prior vaginal 

delivery. 

77 
 

 

Total Event (95%Confidence Interval) Trial of labor 

Flamm, 1994 5022 25 0.005(0.003, 0.007) 

McMahon, 1996 3429 36 0.010 (0.007, 0.015) 

Hibbard, 2001 1324 11 0.008 (0.004, 0.015) 

Bais, 2001 184 8 0.043 (0.019, 0.084) 

Wen, 2004 128960 245 0.002 (0.002, 0.002) 

Loebel,2004 927 12 0.013 (0.007, 0.023) 

Spong, 2007 15323 227 0.015 (0.013, 0.017) 

Gregory, 2008 11480 63 0.005 (0.004, 0.007) 

Kugler, 2008 774 14 0.018 (0.010, 0.030) 

Combined (I-squared = 98.6%, p < 0.001) 0.009 (0.004, 0.020) 

Elective repeat cesarean delivery 

Flamm, 1994 2208 38 0.017 (0.012, 0.024) 

McMahon, 1996 2889 39 0.013 (0.010, 0.018) 

Hibbard, 2001 431 6 0.014 (0.005, 0.030) 

Bais, 2001 68 4 0.059 (0.016, 0.144) 

Wen, 2004 179795 268 0.001 (0.001, 0.002) 

Loebel,2004 481 3 0.006 (0.001, 0.018) 

Spong, 2007 17714 183 0.010 (0.009, 0.012) 

Kugler, 2008 328 18 0.055 (0.033, 0.085) 

Gregory, 2008 29970 153 0.005 (0.004, 0.006) 

Combined (I-squared = 98.9%, p < 0.001) 0.012 (0.005, 0.026) 

0 .02 .04 .06 .08 .1 

Transfusionrate 

(95%confidence interval) 

Figure 21. Transfusion rates for trial of labor versus elective repeat cesarean among all studies 

Study Name N N Transfusion Rate 

Term studies. Four, of the nine studies focused exclusively on women delivering at term 

(Figure 22).93, 97, 108, 204 All four term studies reported higher rates of transfusion among women 

who had a TOL, with two reaching statistical significance.97, 204 The combined risk of transfusion 

was 0.7 percent (95 percent CI: 0.2 to 2.2 percent) for TOL and 0.5 percent (95 percent CI: 0.2 to 

1.3 percent) for ERCD, translating to seven per 1,000 and five transfusions per 1,000, 

respectively. When these studies were combined there was a significantly increased risk of 

transfusion for TOL compared with ERCD (RR, 1.30; 95 percent CI: 1.15-1.47; p<0.001). Using 

0.5 percent as the baseline risk for ERCD, the calculated risk difference was 0.14 percent (95 

percent CI: 0.07 to 0.22 percent), which is equivalent to 1.4 more transfusion per 1,000 for TOL. 

78 
 

Transfusion Rate 

Study Total Event (95% Confidence Interval) 

Trial of labor 

Loebel, 2004 927 12 

Wen, 2004 128960 245 

Spong, 2007 15323 227 

Gregory, 2008 11480 63 

Combined (I-squared = 99.4%, p< 0.001) 

Elective repeat cesarean delivery 

Loebel, 2004 481 3 

Wen, 2004 179795 268 

Spong, 2007 17714 183 

Gregory, 2008 29970 153 

Combined (I-squared = 99.3%, p < 0.001) 

0.0129 (0.0067, 0.0225) 

0.0019(0.0067, 0.0022) 

0.0148 (0.0130, 0.0169) 

0.0055 (0.0042, 0.0070) 

0.0066 (0.0020, 0.0221) 

0.0062 (0.0013, 0.0181) 

0.0015 (0.0013, 0.0017) 

0.0103 (0.0089, 0.0119) 

0.0051 (0.0043, 0.0060) 

0.0046 (0.0016, 0.0132) 

0 .005 .01 .015 .02 .025 .03 

Figure 22. Transfusion rates for trial of labor versus elective repeat cesarean delivery among term 

studies 

Transfusion rate (95% confidence interval) 

When looking at the five studies of women delivering at any gestational age, the combined 

risk of transfusion was 1.2 percent (95 percent CI: 0.7 to 2.3 percent) for TOL and 2.4 percent 

(95 percent CI: 1.3 to 4.3 percent) for ERCD, translating to 12 per 1,000 and 24 transfusions per 

1,000 respectively. There was a significantly reduced risk of transfusion for TOL compared with 

ERCD (RR, 0.48; 95 percent CI: 0.30 to 0.79; p=0.003). Using 2.4 percent as the baseline risk 

for ERCD, the calculated risk difference was -1.26 percent (95 percent CI: -1.71 to -0.52 

percent), which is equivalent to 12.6 fewer transfusions per 1,000 for TOL. 

Group assignment. The disparities among the pooled analyses raise questions about whether 

other factors may be playing a role. Two studies provided separate results for VBAC, ERCD, 

and cesarean after TOL.95, 234 In both studies, VBAC had the lowest rate of transfusion, followed 

by cesarean after TOL, while ERCD had the highest rate of transfusion. This suggests the 

influence of term gestational ages may be related to increased transfusions with cesarean after 

TOL; however, the term gestation delivery studies did not report these outcomes. 

Maternal factors. The pooled risk is strongly influenced by the largest study, which included 

all levels of care as well as relied on ICD-9 codes for data gathering. This study found opposing 

results to the general trends seen with the other studies in this group, and is likely strongly 

79 
 

contributing to the effect seem with the pooled data.108 Two studies examined the affect of 

medical conditions upon transfusion rates.93, 204 Both studies found an association between highrisk pregnancies with medical conditions and increased transfusion. Gregory found that among 

high-risk patients, women who delivered by ERCD had more transfusions than those who had a 

TOL (0.92 versus 0.78 percent, p=NS) and that the overall rate of transfusions was greater 

among higher risk pregnancies compared with the low-risk group (0.46 versus 0.33 percent, 

p=NS).93 Similarly, using data from the MFMU cohort, Spong et al divided the type of cesarean 

delivery into ERCD and indicated repeat cesarean (IRCD) with and without labor, and found the 

highest proportion of transfusion with IRCD in the absence of labor, again suggesting an 

influence of maternal co-morbid conditions contributing to increased transfusion risk.204 An 

analysis of the MFMU cohort focusing only on low-risk ERCD found a statistically significant 

increase in transfusion with TOL compared with ERCD prior to labor (one versus 1.7 percent, 

p<0.001), further supporting the idea that maternal co-morbid conditions influence the risk of 

transfusion.221 In this same cohort, however, increasing maternal BMI and morbid obesity were 

not found to be associated with increased risk of transfusion in the MFMU cohort.78 

Hospital setting. One study evaluated the impact of hospital delivery volume on the risk of 

transfusion.108 In low volume hospitals (less than 500 deliveries per year) the odds of transfusion 

with TOL was 1.39 (1.02 to 1.88) compared with ERCD. In high volume centers (greater than 

500 deliveries per year) the odds ratio was 1.66 (1.32 to 2.08) for transfusion with TOL 

compared with ERCD.108 This study differs in its findings from other studies as described 

previously; confounding factors that may contribute to this difference is that this review of a 

birth registry was based on ICD-9 codes; also, unlike the other studies, this study does report 

only on Canadian hospitals, and includes multiple different levels of hospital acuity. 

Influence of prior deliveries. Within the MFMU cohort, multiple studies evaluated the impact 

of previous deliveries on the risk of transfusion.80, 181, 192, 236 Subjects with only one prior 

cesarean delivery undergoing TOL had a rate comparable with ERCD (1.6 versus 1.5 percent), 

while those with multiple prior cesareans undergoing TOL had a higher transfusion rate 

compared with ERCD (3.2 versus 1.5 percent).80 This study did not distinguish those with ERCD 

undergoing multiple cesareans versus first RCD. However, increasing number of cesareans was 

found to be a risk factor for transfusion.236 The MFMU cohort had a decreasing rate of 

transfusion with increasing number of previous VBACs, implying a protective role for prior 

vaginal delivery against transfusion (zero prior VBAC: 1.89 percent; one prior VBAC: 0.24 

percent; two or more prior VBAC: 0.99 percent; p=0.002).192 One study of this cohort found no 

difference in women with a prior vaginal delivery when comparing those who were induced with 

those who went into spontaneous labor (odds ratio 1.13; 95 percent CI: 0.66 to 1.95). However, 

in those women without a previous vaginal delivery, there was a higher rate of transfusion in the 

induced group compared with the spontaneous labor group, suggesting a role of induction as a 

risk for transfusion in women with no prior vaginal delivery only (odds ratio 1.65; 95 percent CI: 

1.10 to 2.48).156 

Hemorrhage. Six fair quality cohort studies report on the occurrence of hemorrhage for TOL 

versus ERCD.76, 93, 95, 100, 203, 234 Among the six studies the rates of hemorrhage with ERCD 

ranged from 0.3 percent to as high as 29 percent. In general, studies reported increased 

occurrence of hemorrhage associated with ERCD compared to TOL. However, studies were 

inconsistent regarding the definition of hemorrhage. Several studies did not report the process by 

which this outcome was measured; studies that quantified blood loss used different amounts of 

blood loss to qualify as hemorrhage. The highest rate of hemorrhage was from a study that 

defined hemorrhage as greater than 500mL blood loss.76 Further complicating evaluation of these 

80 
data is the known difficulty in recording blood loss. Multiple studies demonstrate physician 

perception of blood loss differs from actual blood loss, impeding accurate recording of this 

measure.237, 238 All studies found a trend toward increased blood loss with ERCD. However, none 

of the studies found a statistically significant difference between hemorrhage rates for TOL and 

ERCD. Because these studies did not define hemorrhage similarly, these data were not pooled 

for analysis. Interesting findings from individual studies are discussed below. 

Term studies. Only one of the six studies,93 provided data regarding hemorrhage specifically 

in term pregnancies. In this study, low-risk patients were separated from high-risk patients based 

on antenatal conditions. The low-risk group had a lower rate of hemorrhage with TOL compared 

with ERCD (2.36 versus 6.82 percent, p=NS); however in the high-risk group, there was an 

increase in hemorrhage with TOL compared with ERCD (3.26 versus 1.57 percent). In the one 

study that reported both, the rates of transfusion are in direct opposition to the rates of 

hemorrhage for every subset, such that in groups with higher rates of hemorrhage, there were 

overall fewer transfusions given.93 This was a study that used an administrative database and 

demonstrates the difficulty in reporting and interpreting a subjective term such as hemorrhage. 

Group assignment. Three studies separated the TOL data by VBAC and cesarean after a 

TOL.95, 203, 234 Rates of hemorrhage for VBAC ranged from 0.3 to 6 percent, compared with 

cesarean after TOL which ranged from 0.86 to 14.8 percent. In three of these studies, cesarean 

after a TOL had the highest rate of hemorrhage compared to VBAC and ERCD. One study found 

a statistically significant increase in hemorrhage with ERCD compared to cesarean after a TOL 

and VBAC (0.91 versus 0.64 versus 0.81 percent, p<0.001).95 This study did not define 

hemorrhage; in addition, this university-based Israeli study focused on a grand multiparous 

subgroup, possibly confounding the results given the global increased risk of hemorrhage. One 

database study from Norway described the incidence of postpartum hemorrhage. Though it did 

not specifically evaluate women undergoing TOL or ERCD, it did find 333 cases of hemorrhage 

in women with a history of previous cesarean delivery. This study found an increased risk of 

hemorrhage with both vaginal delivery (odds ratio 1.63; 95 percent CI: 1.34 to 1.98) and 

emergency cesarean (1.41; 95 percent CI: 1.12 to 1.78) in women with a previous history of 

cesarean compared to women without a history of cesarean.239 This study found no difference in 

hemorrhage between these two groups for pre-labor cesarean; however, for women with prior 

cesarean, pre-labor cesarean carried a 28 percent higher risk of hemorrhage compared to 

spontaneous labor delivery.239 

Summary and strength of evidence on transfusion/hemorrhage. Overall, evidence 

regarding the rate of hemorrhage for TOL and ERCD is low due to inconsistency in definitions 

and subjectivity in measurement. In general, studies reported increased occurrence of 

hemorrhage associated with ERCD compared to TOL. There was only one study that provided 

data for term populations. This study suggested that medical complications may modify the 

effect of route of delivery upon hemorrhage with low-risk patients similarly having higher 

hemorrhage rates for ERCD but with high-risk patients experiencing higher rates of hemorrhage 

for TOL. Further studies are needed to understand the true relationship. 

Infection 

Twenty-two studies of good or fair quality evaluated infectious morbidity (e.g., fever, infection, 

endometritis, or chorioamnionitis) in TOL compared with ERCD (see Appendix R for study 

details).10, 76-79, 81, 89, 95, 97, 108, 114, 201-205, 221, 234, 240-243 Ten studies 10, 89, 95, 97, 108, 202-204, 234, 240 report 

on infection in some manner. As shown in Figure 23, there was no significant difference in 

infection between TOL and ERCD. ). The I

2

 statistic for heterogeneity was 89 percent. However, 

81 
 

the confidence in the magnitude and direction of the estimates from this body of literature is low 

due to inconsistencies in definitions, indirect evidence, and high risk of bias. Details in the 

specific infections reported in these studies are described below. 

Figure 23. Rates of infection for trial of labor versus elective repeat cesarean delivery among all 

studies 

Infection rates 

Study Total Event (95% Confidence interval) 

Trial of labor 

Martin, 1983 162 11 0.068 (0.034, 0.118)

Eriksen, 1989 71 2 0.028 (0.003, 0.098)

McMahon, 1996 3429 43 0.013 (0.090, 0.017)

Chauhan, 2001 30 17 0.567 (0.374, 0.745)

Hibbard, 2001 1324 277 0.209 (0.188, 0.232)

Durnwald, 2004 522 55 0.105 (0.080, 0.135)

Loebel, 2004 927 23 0.025(0.016, 0.037)

Wen, 2004 128960 487 0.004 (0.003, 0.004)

Spong, 2007 15323 442 0.029 (0.026, 0.032)

Kugler, 2008 774 19 0.025 (0.015, 0.038)

Combined (I-squared = 99.7%, p < 0.001) 0.046 (0.015, 0.135)

Elective repeat cesarean delivery 

Martin, 1983 547 54 0.098 (0.075, 0.127)

Eriksen, 1989 68 1 0.015 (0.0003, 0.079)

McMahon, 1996 2889 63 0.022 (0.017, 0.028)

Chauhan, 2001 39 10 0.256 (0.130, 0.421)

Hibbard, 2001 431 56 0.130 (0.100, 0.165)

Durnwald, 2004 246 5 0.020 (0.007, 0.047)

Loebel, 2004 481 11 0.023 (0.011, 0.041)

Wen, 2004 179795 837 0.005 (0.004, 0.005)

Spong, 2007 17714 361 0.020 (0.018, 0.023)

Kugler, 2008 328 4 0.01 2(0.003, 0.031)

Combined (I-squared = 99.4%, p < 0.001) 0.032 (0.013, 0.073)

0 .1 .2 .3 .4 .5 .6
 

Overall infection rate 95% Confidence interval 

Endometritis. Six studies of good or fair quality compared endometritis in TOL with 

ERCD.89, 95, 203, 221, 240, 241 Overall, rates of endometritis were higher in TOL when compared with 

ERCD. Rates of endometritis in TOL ranged from 0.8 to 30 percent. The rates of endometritis in 

ERCD ranged from 1.2 to 18 percent. The upper ranges of these figures both derive from the 

same study focusing on morbidly obese patients, suggesting an influence of obesity on the risk of 

infection.240 

The MFMU cohort evaluated endometritis in TOL compared with ERCD (Appendix R).221 A 

separate report on this same cohort specifically evaluated BMI and the risk of endometritis in 

morbidly obese patients.78 There was a statistically significant increase in the rate of endometritis 

with increasing BMI in patients undergoing a TOL. Additionally, there was a statistically 

significant increased odds of endometritis for TOL compared with ERCD in morbidly obese 

82 
(BMI greater than 40) subjects. (odds ratio 2.4; 95 percent CI: 1.7 to 3.5).78 This again suggests 

maternal weight influences the risk of endometritis in this population. 

In studies where outcomes of TOL were evaluated separately, cesarean after labor patients 

consistently had a higher rate of endometritis than did VBAC or ERCD patients.89, 95, 203 This 

suggests the increased rates of endometritis seen with TOL may be more associated with 

cesarean delivery than with the labor itself. 

Chorioamnionitis. In total, two cohort studies compared chorioamnionitis rates for TOL and 

ERCD in deliveries.89, 95 Both found a higher rate of chorioamnionitis in the TOL group. Based 

on this, there is evidence that chorioamnionitis is associated with TOL, regardless of ultimate 

mode of delivery. 

Wound infection. Wound infection was evaluated in three cohort studies.10, 203, 240 Two of 

the three found ERCD to be associated with a higher rate of wound infection, 10, 203 while one 

found a higher rate with TOL. This study was limited to women over 300lbs at delivery, which 

complicates any direct comparison of this data with the others.240 None of these studies reached 

statistical significance with their findings. 

Fever. Ten good or fair quality cohort studies compared maternal fever between TOL and 

ERCD.10, 76, 77, 79, 81, 89, 95, 201, 202, 205 As shown in Figure 24, the combined absolute risk for any 

fever with TOL was 6.5 percent (95 percent CI: 4.4 to 9.3 percent) which translates to 65 per 

1,000 (95 percent CI: 44 to 93 per 1,000) and for ERCD was 7.2 percent (95 percent CI: 2.5 to 

18.9 percent) which translates to 72 per 1,000 (95 percent CI: 25 to 189 per 1,000). Compared 

with ERCD, TOL demonstrated a significant decrease in the risk of fever (RR, 0.63; 95 percent 

CI: 0.43 to 0.91; p=0.013). Using 7.2 percent as the baseline risk for ERCD, the calculated risk 

difference was -2.7 percent (95 percent CI: -4.10 to -0.68 percent), which is equivalent to 27 

fewer fevers per 1,000 from the TOL There was considerable heterogeneity among studies (I

2

 = 

92.7 percent), which demonstrates the variability in the definition of the term “fever” among 

studies. Only one study in this pooled analysis defined fever by an absolute number (greater than 

38 degrees Celsius); it is interesting to note this study did serve as the most apparent outlier in 

the pooled analysis.79 When this study was excluded from analysis, the combined risk of fever 

for ERCD group was 11.0 percent and TOL still had a significantly lower risk of fever (RR, 

0.58; 95 percent CI: 0.40 to 0.82; p=0.002). Using 11.0 percent as the baseline risk for ERCD, 

the calculated risk difference was -4.68 percent (95 percent CI: -6.58 to -1.95 percent), which is 

equivalent to 47 fewer fevers per 1,000 for TOL. The I

2

 statistic for heterogeneity remained 92.7 

percent, demonstrating that this outlier did not explain the heterogeneity seen among studies. 

Four cohort studies evaluated maternal fever stratified by outcome of TOL.81, 89, 95, 201 Three 

of the four studies found increased rates of fever in cesarean after a TOL compared with 

VBAC.81, 89, 201 This suggests a higher febrile morbidity associated with cesarean delivery after 

labor compared with VBAC. However, in all but one of these studies ERCD continued to have 

the highest rate of febrile morbidity, suggesting surgery as a risk factor for maternal infectious 

morbidity. This would imply the rate of fever seen with TOL may be influenced by the higher 

risk of fever with RCD after a TOL and not be associated with VBAC. The one outlier study in 

this group found a rate of 32 percent for cesarean after a TOL compared with 18 percent for 

ERCD. However, the population of this study was limited to subjects with two prior cesarean 

deliveries. Increased complications with second cesarean after labor may have influenced the 

higher rates seen with ERCD.81 Within women who underwent a TOL, there appears to be an 

increased risk for febrile morbidity with operative delivery. 

83 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 24. Rates of fever for trial of labor versus elective repeat cesarean delivery among all 

studies 

Study N Total N Event 95% Confidence interval 

Trial of labor 

Eglington, 1984 376 33 0.088 (0.061, 0.121) 

Phelan, 1987 1796 159 0.089(0.076, 0.103) 

Eriksen, 1989 71 4 0.056 (0.016, 0.138) 

Flamm, 1994 5022 638 0.127 (0.118, 0.137) 

Mcmahon, 1996 3424 171 0.050 (0.043, 0.058) 

Hook, 1997 492 38 0.077(0.055, 0.104) 

Bias, 2001 184 16 0.087 (0.051, 0.137) 

Durnwald, 2004 522 27 0.052 (0.034, 0.074) 

Cahill, 2006 5041 329 0.065 (0.059, 0.072) 

Kugler, 2008 619 9 0.015 (0.007, 0.027) 

Combined (I-squared = 96.0%, p < 0.001) 0.065 (0.044, 0.093) 

Elective repeat cesarean delivery 

Eglington, 1984 495 176 0.356 (0.313, 0.399) 

Phelan, 1987 314 56 0.178 (0.138, 0.225) 

Eriksen, 1989 68 7 0.103 (0.042, 0.201) 

Flamm, 1994 2208 362 0.164 (0.149, 0.180) 

Mcmahon, 1996 2889 185 0.064 (0.055, 0.074) 

Hook, 1997 497 0 0 (0, 0.0074) 

Bias, 2001 68 7 0.103 (0.042, 0.201) 

Durnwald, 2004 246 6 0.024 (0.009, 0.052) 

Cahill, 2006 1578 294 0.186 (0.167, 0.206) 

Kugler, 2008 328 10 0.030 (0.015, 0.055) 

Combined (Test of heterogeneity is based on 0.072 (0.025, 0.189) 

Fisher’ Exact test, p < 0.001) 

-.1 0 .1 .2 .3

 Fever rate (95% Confidence interval) 

Summary and strength of evidence on infection. Overall, the evidence regarding rate of 

both infection (all definitions) and fever for women with a prior cesarean delivery is low in 

strength with inconsistent definitions, high-risk of bias and indirect evidence. The high 

heterogeneity in these studies demonstrates the variability in the definition of the term “fever” 

among studies. Overall there was no significant difference in infection between TOL and ERCD. 

Surgical injury 

In good or fair quality cohort studies, surgical injury was defined differently between studies 

and variably reported on. Seven studies compared surgical injury between TOL and ERCD.10, 78, 

80, 97, 204, 205, 236 Four of these are from the same cohort of patients (MFMU); however they report 

differently on surgical injury rates and therefore are presented separately (Table 13).78, 80, 204, 236 

Overall, these were found to be rare events. None of the stratifications from the MFMU 

studies found a significant difference between ERCD and TOL for rate of surgical injury.78, 80, 204, 

236 When a specific injury was evaluated, such as bladder, there did tend to be an increased rate 

84 
 

 

of injury with a cesarean after a TOL. However, this trend was not found to be statistically 

significant.205 

One case-control study evaluating women with bladder injury at the time of cesarean 

delivery found attempted VBAC to be proportionately higher in the cases compared with 

controls (64 versus 22 percent, p<0.1) This study found no difference in type of uterine incision 

with risk of bladder injury.244 

One study of 3,164 women evaluated the impact of skin incision direction on the risk of 

bowel or bladder injury. This retrospective study found an increased odds ratio of bladder injury 

with a midline sub-umbilical incision compared with a Pfannenstiel (6.7; 95 percent CI: 2.6 to 

16.5). The RR for bowel injury was also increased with vertical incision at five and a half fold 

risk. After multivariate analysis, vertical abdominal incision remained a significant risk factor for 

bladder injury at the time of cesarean. There was a trend toward increased injury with increasing 

numbers of cesarean deliveries, though this was not statistically significant.245 

85 
Table 13. Surgical injury rates for trial of labor versus elective repeat cesarean delivery 

Author, year, quality rating 

Country/ Setting 

Study description N Surgical injury (per 10,000) Sum

All studies, all gestational ages Cahill, 2006205 16 

University and community hospitals 

Retrospective cohort 

6,619 Bladder injury 

TOL: 26/5041 (51) ERCD: 7/1578(44) 

VBAhigh

Loebel, 200497 Community 

teaching hospital 

Retrospective cohort 

1,408 Operative injury 

(includes lacerations of the bowel, bladder, ureter, or uterine artery) TOL: 4/927 (40) ERCD: 2/481 (40) 

No dgrou

McMahon, 199610 

Canada national registry 1986-1992 

Retrospective cohort population based longitudinal study 

6,138 Extension with laceration of uterine arteries, 

laceration of bladder, ureters, bowel TOL:41/3429 (130) TOL-CD: 39/1287 (300) ERCD: 18/2889 (60) 

TOL incr

Maternal-Fetal Medicine Units network studies Silver, 2006236 

19 university hospitals U.S. academic 1999-2002 

MFMU network cohort 

30,132 # RCD 1st 2nd 3rd 4th 5th 6th The 

are propoveincrwith numove

Bowel injury (per 10,000) 

10 5 10 30 0 110 

Bladder per 10,000 

10 9 30 110 190 450 

Ureter per 10,000 

3 1 2 7 40 110 

Wound Dehiscence Per 10,000 

40 10 20 20 80 0 
Table 13. Surgical injury rates for trial of labor versus elective repeat cesarean delivery 

Author, year, Country/ Study quality rating Setting description N Surgical injury (per 10,000) SumSpong, MFMU 39,117 Composite: broad ligament injury, cystotomy, bowel In a 

2007*204 Network injury, ureteral injury pres

U.S. TOL: 57 (37) incr

academic 1999-2002 

 ERCD (no labor): 45 (30);  ERCD (with labor): 14 (51)

surg

 IRCD (no labor): 23 (46);  IRCD (with labor): 6 (56 

Hibbard, U.S. 

28,446 

Composite: broad ligament hematoma, cystotomy, The

2006*78 academic TOL: bowel injury, or ureteral injury com

1999-2002 14,142 

ERCD: All TOL by BMI 

incr

14,304 a) 18.5-24.9: 6/1344 (44) 

b) 25.0-29.9: 23/4747 (48) c) 30-39.9: 14/6413(22) d) >40: 10/1638 (61) p = .58 

Landon, MFMU17,890 Composite: The

200680 Network U.S. academic 1999-2002 broad ligament hematoma, cystotomy, bowel injury, or ureteral injury 1 prior CD: 60/16,915 40) Multiple prior CD: 4/975 40) ERCD: 36/6035 (60) sign

surgor mVBA

Abbreviations: BMI=body mass index; CD=cesarean delivery; ERCD=elective repeat cesarean delivery; IRCD=indicated re

MFMU=Maternal-Fetal Medicine Units Network; RCD=repeat cesarean delivery; TOL=trial of labor; TOL-CD=trial of labor f

delivery; U.S.=United States; VBAC=vaginal birth after a cesarean 
Summary of surgical injury. Rate of surgical injury may be increased with TOL but 

definitive studies are lacking. Vertical skin incision increases risk of surgical injury to the 

bladder. 

Hospital Stay 

Hospital stay was reported as length of total stay in days. A total of eight cohort studies 

examined length of stay data in the U.S., comparing ERCD and TOL (Appendix S).77, 79, 81, 93, 97, 

201, 202, 234 All studies were affiliated with teaching institutions. In general, as expected, ERCD 

had a longer length of hospital stay compared with TOL. The large MFMU cohort studies did not 

report length of stay data comparing ERCD with TOL. One study did evaluate the risk of 

extended stay, defined as greater than 4 days, with ERCD compared with TOL in morbidly obese 

patients; this study found increased length of stay with ERCD (odds ratio 1.2; 95 percent CI: 1.1 

to 1.4).78 

Pooled analysis of any gestational age studies. For any GA cohorts, the pooled analysis 

using a random effects model demonstrated that the mean length of stay for TOL was 2.55 days 

(95 percent CI: 2.34 to 2.76 days). Pooled mean length of stay for ERCD was 3.92 days (95 

percent CI: 3.56 to 4.29 days). There was significant heterogeneity among studies (Q=221.06, 

p<0.001) and the I

2

 statistic for heterogeneity was 98.2 percent (between-study heterogeneity 

accounts for 98.2 percent of the total heterogeneity) (Figure 25). 

Summary of hospital stay. Elective repeat cesarean delivery is associated with a longer 

hospital stay compared with TOL. 

88 
 

 

 

 

 

 

 

 

 

 

 

 

Figure 25. Length of stay for trial of labor versus elective repeat cesarean delivery among any 

gestational age studies 

Study N Mean Standard deviation 95% Confidence interval 

Trial of labor 

Eriksen, 1989 

Flamm, 1994 

71 

5022 

3.1 

2.38 

1.6 

1.3 

3.10 (2.73, 3.47) 

2.38 (2.34, 2.42) 

Hibbard, 2001 

Loebel, 2004 

1324 

927 

3.26 

2.02 

2.61 

1.35 

3.26 (3.12, 3.40) 

2.02 (1.93, 2.11) 

Gregory, 2008 8292 2.25 1.06 2.25 (2.23, 2.27) 

Combined (I-squared = 98.5%, p = 0.000) 2.55 (2.34, 2.76) 

Elective repeat cesarean delivery 

Eriksen, 1989 

Flamm, 1994 

68 

2207 

5.4 

3.54 

2 

1.1 

5.40 (4.92, 5.88) 

3.54 (3.49, 3.59) 

Hibbard, 2001 431 5.04 3.09 5.04 (4.75, 5.33) 

Loebel, 2004 

Gregory, 2008 

481

 20834 

3.14 

3.02 

0.91 

0.78 

3.14 (3.06, 3.22) 

3.02 (3.01, 3.03) 

Combined (I-squared = 99.5%, p = 0.000) 3.92 (3.56, 4.29) 

0 1 2 3 4 5 6 

Mean length of stay (95% Confidence interval) 

Pelvic Floor 

One study evaluated the effect of VBAC on perineal trauma in deliveries over 36 weeks GA. 

After controlling for age, parity, and episiotomy, those women who had a VBAC as their second 

delivery had an odds ratio of 5.46 (95 percent CI: 3.69 to 8.08) of severe perineal trauma 

compared with women with a previous vaginal delivery. In contrast, the odds ratio for a 

primiparous woman was 4.08 (95 percent CI: 3.16 to 5.28).246 A second study noted a 34 percent 

prevalence of third or fourth degree perineal laceration following episiotomy in women 

undergoing VBAC; however no comparisons were made to RCD after a TOL.137 No studies 

evaluated risk of urinary or fecal incontinence following ERCD versus TOL. 

Deep Vein Thrombosis 

Three studies evaluated thromboembolic disease between ERCD and TOL.192, 203, 221 A 

multicenter study evaluating maternal risk and thromboembolic disease found the lowest rate of 

embolic disease with TOL after one prior cesarean delivery compared with subjects undergoing 

either ERCD or VBAC after multiple cesarean deliveries (0.04 percent versus 0.1 and 0.1 

percent).221 

89 
Special Considerations 

Effect of hospital setting. In total, eight studies reported outcomes in both community and 

academic centers.10, 61, 77, 93, 97, 98, 108, 205 Three of these studies reported on the same cohort of 

patients.61, 98, 205 Of these eight studies, only one specifically described the community data 

separately.108 As described previously, this study evaluated maternal risk with ERCD, TOL, 

VBAC, and RCD using the Canadian birth registry. This evaluation focused specifically on the 

risks of each mode of delivery in low volume (less than 500 deliveries per year) and high volume 

(greater than 500 deliveries per year) medical centers. This study demonstrated an increased odds 

of short-term complications in low volume maternity wards. Specifically, the odds ratio of a 

particular outcome associated with TOL when compared with ERCD were higher for death (odds 

ratio 2.68; 95 percent CI: 0.16 to 45.5 versus odds ratio 0.16; 95 percent CI: 0.02 to 1.29) and 

uterine rupture (odds ratio 4.02; 95 percent CI: 2.48 to 6.51 versus odds ratio 2.30; 95 percent 

CI: 2.04 to 2.59) in low volume maternity wards.108 

Abnormal placentation. Prior cesarean delivery is a risk factor for abnormal placentation in 

future pregnancies. As the number of cesarean deliveries continues to rise, the incidence of 

abnormal placentation, which includes placenta previa, accreta, increta, and percreta, is 

anticipated to increase as well. Abnormal placentation has been associated with both maternal 

and neonatal morbidity including need for antepartum hospitalization, preterm delivery, 

emergent cesarean delivery, hysterectomy, blood transfusion, surgical injury, intensive care unit 

(ICU) stay, and fetal and maternal death. In order to effectively counsel women about their risk 

of complications due to the placenta in future pregnancies, it is essential to have a clear 

understanding of the incidence of these potentially life-threatening complications in women with 

prior cesarean delivery. 

Incidence of abnormal placentation following cesarean section. Eighty-two full text articles 

were reviewed to evaluate the evidence regarding the incidence and outcomes of pregnancies 

complicated by abnormal placentation, including abruption, placenta previa, and placenta 

accreta, following prior cesarean delivery. Nineteen articles met inclusion criteria and consisted 

of eight good or fair quality cohort studies,11, 220, 236, 247-251 seven fair quality case-control 

studies,176, 235, 252-256 and four good or fair quality case series.257-260 Individual studies provided 

evidence for one or more of the separate topics of abruption, previa, and accreta, respectively. 

The studies that made up the body of evidence for each subset of abnormal placentation are listed 

below. 

Abruption. Six fair quality studies, five cohort studies11, 247, 249-251 and one case-control 

study235 examined abruption following a prior cesarean delivery. Studies were inconsistent in 

their definition for placental abruption with three studies relying on ICD-9 coding11, 247, 250 and 

no definition offered by the other three.235, 249, 251 

The overall incidence of placental abruption with any prior cesarean delivery was 1.2 to 1.5 

percent.250, 251 For women with one prior cesarean delivery, the odds ratio for abruption was 1.0 

to 1.3 and only one of four studies reached statistical significance. The majority of studies did 

not find an increased incidence of abruption in women with increasing numbers of prior cesarean 

delivery (Table 14). 

90 
 

Table 14. Abruption based on number of prior cesarean deliveries 

Studies N 

Adjusted OR 

(95% CI) or P 

value 

N/# cesarean 

delivery 

per/ 

1,000 

Any prior cesarean delivery 

Odibo, 2007250 25,076 1.2% 

(309/25076) 

13 per 1,000 

13 

Rouse, 2006251 57,169 1.5% 

(504/33683) 

Zero prior cesarean deliveries 

Rouse, 2006251 57,169 3.4% 

(807/23486) 

1 prior cesarean delivery 

Hemminki, 2005247 72,200 1.21 

(0.96 to 1.53) 

10.3 

Lydon-Rochelle, 200111 96,975 1.3 

(1.1 to 1.5) 

13.7 

Nisenblat, 2006249 940 1.02% (5/491) 

Odibo, 2007250 25,076 1 

(0.9 to 1.0) 

1.2% 

(246/20236) 

>1 prior cesarean delivery 

Rouse, 2006251 57,169 1.5% 

(504/33682) 

2 prior cesarean deliveries 

Hemminki, 2005247 72,200 1.01 

(0.52 to 1.97) 

10.3 

Odibo, 2007250 25,076 1 

(0.8 to 1.3) 

1.3% (50/3976) 

>2 prior cesarean deliveries 

Nisenblat, 2006249 940 p>0.9 1.1% (3/277) 

3 prior cesarean deliveries 

Odibo, 2007250 25076 1.2 

(0.7 to 2.1) 

1.5% (13/863) 

>3 prior cesarean deliveries 

Juntunen, 2004235 73000 p=0.024 3.4% (149) 

Abbreviations: CI=confidence interval; OR=odds ratio 

Women with abruption were more likely to require blood transfusion, but the incidence did 

not increase with increasing number of cesarean delivery. Of women without a prior cesarean 

delivery, 14.3 percent required blood transfusion compared with 14.1 percent in women with one 

or more prior cesarean deliveries without abruption. Other maternal outcomes such as 

hemorrhage and hysterectomy were reported inconsistently such that meaningful analysis of an 

association with abruption and prior cesarean delivery was not possible (Table 15).251 

91 
Table 15. Blood transfusion by number of prior cesarean deliveries 

Studies N 

Adjusted OR 

(95% CI) or P value 

N/abruption 

population 

Zero prior cesarean deliveries 

Rouse, 2006251 57,169 2.9 

(2.2 to 3.7) 

14.3% 

(115/807) 

>1 prior cesarean deliveries 

Rouse, 2006251 57,169 2.6 

(1.8 to 3.7) 

14.1% 

(71/504) 

Abbreviations: CI=confidence interval; OR=odds ratio 

Placenta previa. Eight good or fair quality cohort studies,11, 220, 236, 247-251 five fair quality 

case-control studies,235, 253, 255, 259, 261 and three good or fair case series257, 258, 260 provide the 

primary body of evidence regarding placenta previa following prior cesarean delivery. Only six 

studies provided information on the incidence of placenta previa following prior cesarean 

delivery (Table 16).11, 248, 251, 258, 259, 261 Again, studies differed in their definition for placenta 

previa with two studies using a previa grade scale and the remaining providing individual 

definitions. 

Table 16. Overall incidence of placenta previa 

Studies N N with previa Per /1,000 

Hershkowitz, 1995248 58,633 284 4.8 

Lydon-Rochelle, 200111 96,975 1,100 11.5 

Miller, 1997258 155,670 590 1 in 263 

(incidence) 

Olive, 2005259 375,790 1,612 4.3 

Rouse, 2006251 57,169 900 15.7 

Taylor, 1994261 278,933 Not reported 3.3 

Women with a prior cesarean delivery had a statistically significant increased risk of placenta 

previa compared with women with no prior cesarean delivery (odds ratio 1.48 to 3.95, Table 17). 

The studies conflicted as to whether the risk increased with increasing cesarean deliveries. The 

incidence of previa with one prior cesarean delivery was 0.8 to 1.5 percent. Compared with 

women without a prior cesarean delivery, the odds ratio was 1.2 to 1.9. This was statistically 

significant in four of seven studies. In women with two prior cesarean deliveries, the incidence 

of previa was 1.1 to 2.0 percent with an odds ratio of 1.9 to 2.0; this was statistically significant 

in three of five studies. Two studies limited comparisons to women with one prior cesarean 

delivery versus multiple cesarean deliveries.248, 249 In these studies, no increased risk with 

additional cesarean deliveries was noted. These studies had limited sample size for women with 

multiple cesarean deliveries and previa (N=7 and N=20, respectively).248, 249 The six studies that 

specifically identified women with three or more cesarean deliveries all noted a statistically 

significant increased rate of previa with increasing cesarean deliveries, up to 3.7 percent for 

women with five or more prior cesarean deliveries.235, 236, 248, 250, 253, 258 

92 
Table 17. Incidence of placenta previa by number of prior cesarean deliveries 

Studies N 

Adjusted OR (95% CI) or p value 

N/previa population N/# CD 

N/total population per/1,000 

Any number of prior cesarean deliveries Gilliam, 2002253 2,367 1.59 

(1.21 to 2.08) 

28% (87/316) 

Hershkowitz, 1995248 58,633 2.25 

(1.50 to 3.07) 

21% (60/284) 

Laughon, 2005255 5,824 3.95 

(1.49 to 10.50) 

22.7% (20/88) 

Miller, 1997258 155,670 31.5% 

(186/590) 

Odibo, 2007250 25,076 361/25,076 15 

Olive, 2005259 375,790 2.4 19.5% 

(2.1 to 2.8) (315/1,612) 

Rouse, 2006251 57,169 1.2% 

(394/33,683) 

Taylor, 1994261 278,933 1.48 

(1.13 to 1.95) 

20% (99/490) 

Zero prior cesarean deliveries Gilliam, 2002253 2,367 1 71% (225/316) 

Hershkowitz, 1995248 58,633 0.07% 

0.79 

(21/26,302)

Miller, 1997258 155,670 p=<0.01 0.30% 

Silver, 2006236 30,132 6.42% 

(398/6,201) 

Zelop, 1993260 75,656 1.6% 

(565/35,240) 

1 prior cesarean delivery Gilliam, 2002253 2,367 1.28 

(0.82 to 1.99) 

16% (49/316) 

Hemminki, 2005247 72,200 1.92 2.9 

(1.20 to 3.07) 

Hershkowitz, 1995248 58,633 p<0.0001 1.5% (55/3,573) 15.39 Miller, 1997258 155,670 p=<0.01 0.80% 

Nisenblat, 2006249 940 Not evaluated 1.2% (6/491) 
Table 17. Incidence of placenta previa by number of prior cesarean deliveries 

Studies N 

Adjusted OR (95% CI) or p value 

N/previa population N/# CD 

Lydon-Rochelle, 200111 

96,975 1.4 

1.1, 1.6 

Odibo, 2007250 25,076 RR: 0.9 

(0.8 to 1.0) 

72% (260/361) 

Silver, 2006236 30132 Not significant 1.33% 

(211/15,808) 

2 prior cesarean deliveries Gilliam, 2002253 2,367 1.95 

(1.13 to 3.39) 

9.2% (29/316) 

Hemminki, 2005247 72,200 2.06 

(0.49 to 8.72) 

Hershkowitz, 1995248 58,633 Not significant 1.4% (13/934) 

Miller, 1997258 155,670 p=<0.01 2.00% 

Silver, 2006236 30,132 p=<0.001 1.14% 

(72/6,324) 

>2 prior cesarean deliveries Nisenblat, 2006249 940 p=0.753 1.4% (4/277) 

Lynch, 2003257 67,097 4.8% (12/250) 

Odibo, 2007250 25,076 RR: 1.2 

(0.9 to 1.7) 

20.8% (75/361) 

3 prior cesarean deliveries Gilliam, 2002253 2,367 4.09 

(1.53 to 10.96) 

7/316 

Hershkowitz, 1995248 58,633 Not significant 1.0% (7/675) 

Silver, 2006236 30,132 p=<0.001 2.27% 

(33/1,452) 

>3 prior cesarean deliveries Juntunen, 2004235 73,000 8.4 

(1.0 to 68.0) 

Miller, 1997258 155,670 p=<0.01 4.20% 

Odibo, 2007250 25,076 RR: 1.9 

(1.2 to 2.9) 

7.2% (26/361) 

N/total population 493/95,630 

per/1,000 

6.9 

32.8 

13.91 

10.37 
Table 17. Incidence of placenta previa by number of prior cesarean deliveries 

Studies N 

Adjusted OR (95% CI) or p value 

N/previa population N/# CD 

N/total population per/1,000 

4 prior cesarean deliveries Silver, 2006236 30,132 p=<0.001 2.33% (6/258) 

>4 prior cesarean deliveries Gilliam, 2002253 2,367 8.76 

(1.58 to 48.53) 

2/316 

>5 prior cesarean deliveries Silver, 2006236 30,132 p=<0.001 3.37% (3/89) 

Abbreviations: CD=cesarean delivery; CI=confidence interval; OR=odds ratio; RR=relative risk 
 

 

 

 

 

 

The pooled analysis using a random effects model demonstrated absolute risk of previa 

associated with any number of prior cesarean deliveries was 1.2 percent (95 percent CI: 0.8 to 

1.5 percent), one prior cesarean delivery was 1 percent (95 percent CI: 0.6 to 1.3 percent), two 

prior cesarean deliveries was 1.7 percent (95 percent CI: 1.1 to 2.3 percent) two or more cesarean 

deliveries was 2.3 percent (95 percent CI: 1.1 to 3.4 percent), three or more cesarean deliveries 

was 2.8 percent (95 percent CI: 1.8 to 3.7 percent, Figure 26). This translates to any number of 

prior cesarean deliveries was 12 per 1,000 (95 percent CI: 8 to 15 per 1,000), one prior cesarean 

delivery was 10 per 1,000 (95 percent CI: 6 to 13 per 1,000), two prior cesarean deliveries was 

17 per 1,000 (95 percent CI: 11 to 23 per 1,000) two or more cesarean deliveries was 23 percent 

(95 percent CI: 11 to 34 per 1,000), three or more cesarean deliveries was 28 percent (95 percent 

CI: 18 to 37 per 1,000). 

Figure 26. Incidence of placenta previa by number of prior cesarean deliveries among any 

gestational age studies 

Study Name N N Previa Rate 

Total Event (95% Confidence Interval) 

Any number prior cesarean deliveries
 

Hershkowitz, 1995 75 5182
 0.014 (0.012, 0.018) 

Olive, 2005 315 41641 0.008 (0.007, 0.008) 

Rouse, 2006 394 33683 0.012 (0.011, 0.013) 

Odibo, 2007 361 25076 0.014 (0.013, 0.016) 

Combined 0.012 (0.009, 0.016) (I-squared = 96.1%, p < 0.001) 

One prior cearean delivery
 

Hershkowitz, 1995 55 3573
 0.015 (0.012, 0.020) 

Miller, 1997 102 12750 0.008 (0.007, 0.010) 

Lydon-Rochelle, 2001 137 19875 0.007 (0.006, 0.008) 

Hemminki, 2005 25 8534 0.003 (0.002, 0.004) 

Nisenblat, 2006 6 491 0.012 (0.006, 0.027) 

Silver, 2006 211 15808 0.013 (0.012, 0.015) 

Odibo, 2007 260 20237 0.013 (0.013, 0.015) 

Combined 0.009 (0.007, 0.015) (I-squared = 94.3%, p< 0.001) 

Two prior cesarean deliveries
 

Hershkowitz, 1995 13 934
 0.014 (0.008, 0.024) 

Hemminki, 2005 20 609 0.033 (0.022, 0.050) 

Silver, 2006 72 6324 0.011 (0.009, 0.014) 

Odibo, 2007 75 3976 0.019 (0.015, 0.024) 

Combined (I-squared = 85.9%, p < 0.001) 0.017 (0.011, 0.027)

> Two prior cesarean deliveries
 

Lynch, 2003 12 250
 0.048 (0.027, 0.083) 

Nisenblat, 2006 4 277 0.014 (0.005, 0.038) 

Odibo, 2007 101 4839 0.021 (0.017, 0.025) 

Combined (I-squared = 76.2%, p = 0.015) 0.026 (0.014, 0.048)

> Three prior CD
 

Juntunen, 2004 8 149
 0.054 (0.027, 0.104) 

Silver, 2006 42 1799 0.023 (0.017, 0.031) 

Odibo, 2007 26 863 0.030 (0.021, 0.044) 

Combined (I-squared =60.3%, p = 0.080) 0.030 (0.021, 0.045) 

0 .02 .04 .06 .08 

Previa rate (95% confidence interval) 

The incidence of hysterectomy increased in women with placenta previa depending on the 

number of prior cesarean deliveries (Table18). Women with no prior cesarean delivery and 

previa required hysterectomy in 0.7 to 4 percent of cases compared with 50 to 67 percent in 

women with three or more prior cesarean deliveries. Women with prior cesarean delivery and 

96 
 

 

previa were more likely to require a blood transfusion (odds ratio 15.9; 95 percent CI: 12.0 to 

21.0). Two authors also reported composite major maternal morbidity in women with prior 

cesarean delivery and previa. One study evaluated severe postpartum hemorrhage, acute renal 

failure, ICU admission, mechanical ventilation, shock, disseminated intravascular coagulopathy, 

hysterectomy, other procedures to stop bleeding, and/or death.259 Thirty percent of women with 

prior cesarean delivery and previa experienced major maternal morbidity (odds ratio 3.1; 95 

percent CI: 2.0 to 4.7). A second study combined transfusion, hysterectomy, operative injury, 

coagulopathy, venous thromboembolism, pulmonary edema, and/or death.220 There was a 

statistically significant increase in composite major maternal morbidity with increasing number 

of cesarean delivery from 15 percent with no prior cesarean delivery to 83 percent with three or 

more prior cesarean deliveries (odds ratio 33.6; 95 percent CI: 14.6 to 77.4). 

Table 18. Incidence of hysterectomy in women with previa by number of prior cesarean 

deliveries 

Studies N 

N/# cesarean 

deliveries 

Zero prior cesarean deliveries 

Grobman, 2007*220 70,442 4% (488) 

Zelop, 1993260 75,656 0.7% (4/565) 

1 prior cesarean delivery 

Grobman, 2007*220 70,442 10% (252) 

2 prior cesarean deliveries 

Grobman, 2007*220 70,442 45% (76) 

>3 prior cesarean deliveries 

Grobman, 2007*220 70,442 67% (52) 

Juntunen, 2004235 73,000 50% (4/8) 

>4 prior cesarean deliveries 

Lynch, 2003257 67,097 50% (2/4) 

*Transfusion, hysterectomy, operative injury, coagulopathy, venous thromboembolism, pulmonary 

edema, or death 

Placenta accreta. Three good or fair quality cohort studies236, 249, 258, one fair quality casecontrol study,256 and one fair quality case series study260 examined placenta accreta and prior 

cesarean delivery and the relationship between placenta previa and accreta (Table 19). Two fair 

quality studies evaluated placenta accreta and hysterectomy.252, 254 Studies varied widely on the 

definition of placenta accreta, with one study limited analysis to cases with histopathologically 

confirmed accreta,258 two used histopathologic diagnosis or clinical findings of adherent placenta 

or difficult manual removal,236, 256 one used ICD-9 codes,252 and two did not describe diagnostic 

criteria.249, 254 

Table 19. Overall incidence of placenta accreta 

Studies N 

Adjusted OR 

(95% CI) or P value 

N/previa 

population 

N/total 

population Incidence 

Miller, 1997258 155,670 62/155,670 1 in 2,510 

Silver, 2006236 30,132 1.75 

(1.533 to 1.997) 

Wu, 2005256 64,359 111/64,359 1 in 533 

Zelop 1993260 75,656 75/75,656 

Abbreviations: CI=confidence interval; OR=odds ratio 

97 
Using the designation of placenta accreta as defined by the authors, the incidence of placenta 

accreta increased with increasing number of cesarean deliveries (Table 20). The risk was not 

statistically significant until women had at least two prior cesarean deliveries. Women with one 

prior cesarean delivery had a rate of accreta of 0.3 to 0.6 percent. In comparison to women with 

no prior cesarean delivery, the odds ratio for accreta was 1.3 to 2.16, which was not statistically 

significant. The incidence of accreta rose with increasing prior cesarean deliveries from 1.4 

percent in women with two or more prior cesarean deliveries to 6.74 percent for women with 

five or more prior cesarean deliveries. These results were statistically significant in all three 

studies. The odds ratio increased from 8.6 to 29.8. 

Table 20. Incidence of placenta accreta by number of prior cesarean 

deliveries 

Study N 

Adujused OR (95% CI) or P value 

# with previa 

# with accreta 

Any number of prior cesarean deliveries 

Miller, 1997258 155,670 OR: 19.39 

(11.21 to 33.55) 

Previa: 22% (186) 

Accreta: 73% (45/62) 

Wu, 2005256 64,359 p<0.0001 

Accreta: 50% (55/111) 

Zero prior cesarean deliveries 

Miller, 1997258 155,670 (0.01%) 16/138246 

1 in 68,000 

Silver, 2006236 30,132 0.24% (15/6201) 

1 prior cesarean delivery 

Silver, 2006236 30,132 OR: 1.3 

(0.7 to 2.3) 

0.31% (49/15808) 

Nisenblat, 2006249 940 0.6% (3/491) 

Wu, 2005256 64,359 OR: 2.16 

(0.96 to 4.86) 

2 prior cesarean deliveries 

Silver, 2006236 30,132 OR: 2.4 

(1.3 to 4.3) 

0.57% 

(36/6,324) 

>2 prior cesarean deliveries 

Nisenblat, 2006249 940 1.4% (4/277) 

Wu, 2005256 64,359 OR: 8.62 

(3.53 to 21.07) 

3 prior cesarean deliveries 

Silver, 2006236 30,132 OR: 9 

(4.8 to 16.7) 

2.13% (31/1,452) 

4 prior cesarean deliveries 

Silver, 2006236 30,132 OR: 9.8 

(3.8 to 25.5) 

2.33% (6/258) 

>4 prior cesarean deliveries 

98 
Table 20. Incidence of placenta accreta by number of prior cesarean 

deliveries 

Study N 

Adujused OR (95% CI) or P value 

# with previa 

# with accreta 

Nisenblat, 2006249 940 p=0.023 

4.7% (3/64) 

>5 prior cesarean deliveries 

Silver, 2006236 30,132 OR: 29.8 

(11.3 to 78.7) 

6.74% (6/89) 

Abbreviations: CI=confidence interval; OR=odds ratio 

A statistically significant relationship between placenta previa and placenta accreta in women 

with prior cesarean delivery was noted in two studies.236, 258 As the number of prior cesarean 

deliveries rose, the presence of placenta previa increased the likelihood of placenta accreta from 

3.3 to 4 percent in women undergoing their first cesarean delivery to 50 to 67 percent in women 

with four or more prior cesarean deliveries. Women with accreta had a statistically significant 

increased risk of hysterectomy (odds ratio 43 to 99.5). Additional maternal outcomes such as 

surgical injury, hemorrhage, transfusion, and death and neonatal outcomes were reported 

inconsistently such that meaningful analysis of an association between accreta and prior cesarean 

delivery was not possible (Table 21). 

Table 21. Incidence of placenta accreta with placenta previa by number of prior cesarean 

deliveries 

Study N Adjusted OR (95% CI) or P value 

Zero prior cesarean deliveries 

Miller, 1997258 155,670 4%(15/432) 

Silver, 2006236 30,132 3.3% (13/398) 

1 prior cesarean delivery 

Miller, 1997258 155,670 RR 4.45 

2.09, 9.50 

14% (15/102) 

Silver, 2006236 30,132 11% (23/211) 

2 prior cesarean deliveries 

Miller, 1997258 155,670 23% 

Silver, 2006236 30,132 40% (29/72) 

>2 prior cesarean deliveries 

Miller, 1997258 155,670 RR: 11.32 

(5.59 to 22.92) 

29.7% (25/84) 

3 prior cesarean deliveries 

Miller, 1997258 155670 35% 

Silver, 2006236 30132 61% (20/33) 

4 prior cesarean deliveries 

Miller, 1997258 155670 50% 

Silver, 2006236 30132 67% (4/6) 

>5 prior cesarean deliveries 

Silver, 2006236 30132 67% (2/3) 

Abbreviations: CI=confidence interval; OR=odds ratio; RR=relative risk 

99 
One of the major limitations in analyzing studies regarding placental abnormalities was the 

lack of consistent definition among studies, especially for abruption, which may have resulted in 

misclassification. There was also the potential of surveillance bias as women with prior cesarean 

delivery may have had additional ultrasounds or observation at the time of delivery in 

anticipation of possible placental complications compared with women without known risk 

factors. Studies that used histopathologic diagnosis of accreta were therefore limited to 

hysterectomy patients and may have missed patients managed with conservative therapy. The 

majority of studies relied on retrospective data analysis and are therefore limited by the quality 

and consistency of the original data collection. 

This review confirms prior reports of increasing incidence of accreta in women with previa 

depending on number of prior cesarean deliveries.262 evaluated previa, accreta, and prior 

cesarean delivery in a 1985 paper which was not included in this report due to case collection 

prior to 1980. In the 286 women with previa, the incidence of accreta for women with zero to 

four prior cesarean deliveries was 5, 24, 47, 40, and 67 percent, respectively. Interestingly, the 

incidence of previa and accreta by prior cesarean delivery was similar to later studies except for 

women with one prior cesarean delivery. Miller reported an incidence by number of prior 

cesarean deliveries of 4 percent, 14 percent, 23 percent, 35 percent, and 50 percent,258 and Silver 

found 3 percent, 11 percent, 40 percent, 61 percent, and 67 percent, respectively.236 Although the 

individual patient numbers in each study were limited, the consistent findings suggest that 

women with previa and prior cesarean delivery are at increased risk of placenta accreta and thus 

more likely to require hysterectomy at the time of delivery. 

The incidence of placenta previa or accreta in women with one or two prior cesarean 

deliveries was less than 1.5 percent. The highest risk group was women with three or more prior 

cesarean deliveries with a risk for previa of 3.3 to 4.2 percent and accreta of 4.7 to 6.7 percent. In 

the women with previa, the incidence of hysterectomy was 50-67 percent, and the OR for a 

hysterectomy with accreta was 43-99.5. 

Further studies need to be performed to better evaluate additional risk factors for the 

development of placenta accreta and surgical management to minimize uterine scarring. Women 

desiring large families should be counseled about the risks of abnormal placentation with 

multiple cesarean delivery. As the number of cesarean delivery continues to rise, continued 

evaluation needs to be performed to optimize management of women with abnormal placentation 

and minimize maternal and neonatal morbidity and mortality. 

Summary of abnormal placentation. The risk of abruption for women with any prior cesarean 

ranges from 0.10 to 0.15 percent. The risk does not appear to increase with prior cesarean or 

number of prior cesarean deliveries. Women with a prior cesarean delivery had a statistically 

significant increased risk of placenta previa compared with women with no prior cesarean at a 

rate of 1.2 percent (95 percent CI: 0.8 to 1.5 percent). The incidence increased with increasing 

number of prior cesarean deliveries. A prior cesarean is a significant risk factor for maternal 

morbidity in women with previa. Compared with previa patients without a prior cesarean 

delivery, women with one prior cesarean and previa had a statistically significant increased risk 

of blood transfusion (15 versus 32.2 percent), hysterectomy (0.7 to 4 percent versus 10 percent), 

and composite maternal morbidity (15 versus 23 to 30 percent). For women with three or more 

prior cesarean deliveries and previa, the risk of hysterectomy and composite maternal morbidity 

rose significantly (0.7 to 4 percent versus 50 to 67 percent and 15 versus 83 percent, 

respectively). The incidence of placenta accreta rose with an increasing number of prior cesarean 

deliveries. The results were statistically significant for women with two or more prior cesareans 

100 
 

 

 

 

(odds ratio 8.6 to 29.8). Women with placenta previa are at increased risk for placenta accreta, 

and the risk increased with the increasing number of prior cesareans. Women with more than 

three prior cesareans and previa had a 50 to 67 percent incidence of accreta. 

Maternal complications associated with multiple cesarean deliveries. As the number of 

women who attempt TOL decreases, the obvious consequence is an increase in the number of 

RCD. Conventional wisdom has suggested questioning women with a prior cesarean delivery 

about their plans for future childbearing as part of the discussion regarding mode of delivery due 

to the increased risk of multiple cesarean deliveries, but the actual risks remains unclear. 

Maternal morbidity resulting from multiple cesarean deliveries may consist of adhesions, 

hemorrhage/transfusion, surgical injury, postoperative infection, hysterectomy, abnormal 

placentation, and death. 

The evidence regarding the outcome of multiple cesarean deliveries is limited and consists of 

11 good or fair quality studies.81, 220, 235, 236, 249, 251, 252, 254, 257, 260, 263 

Hemorrhage. Three fair quality cohort studies evaluated the impact of multiple cesarean 

deliveries on maternal hemorrhage and/or blood transfusion rates (Table 22).249, 251, 263 

Definitions of hemorrhage varied. Rouse et al used MFMU data to identify women who received 

a transfusion of packed red blood cells prior to hospital discharge.251 Among women undergoing 

primary cesarean delivery, 3.2 percent (762/23486) received a blood transfusion. Of women with 

a prior cesarean delivery, the percentage of women with blood transfusions increased with 

increasing number of prior cesarean delivery from 1.8, 2.6, 4.3, 4.6, and 14.6 percent from one 

prior to five or more cesarean deliveries, respectively. The odds ratio for women with five or 

more cesarean deliveries was 7.6 (95 percent CI: 4.0 to 14.3). Nisenblat et al compared outcomes 

for women at a single institution in Israel undergoing a second versus three or more cesarean 

deliveries.249 Women were identified who experienced “excessive blood loss” of greater than 

1000 mL or were transfused two or more units. Among women having their second cesarean 

delivery, 3.3 percent (16/491) met this definition compared with 7.9 percent (22/277) of those 

with two or more prior cesarean delivery (odds ratio 2.3; 95 percent CI: 1.1 to 4.5). Macones et 

al performed a secondary analysis of a multicenter, retrospective cohort study and examined 

incidence of blood transfusion.263 In women with two prior cesarean deliveries who did not 

attempt a TOL, 1.18 percent of 2,888 women received a transfusion (odds ratio 0.54; 95 percent 

CI: 0.23 to 1.27). These studies suggest that overall rates of hemorrhage/transfusion are less than 

5 percent but the risk appears to increase with increasing numbers of cesarean delivery. 

Table 22. Multiple cesarean deliveries effect on rates of hemorrhage 

Studies 

Adjusted odds ratio 

95% CI or P value N 

Zero prior cesarean deliveries 

Rouse, 2006251 3.2% (762/23486) 

1 prior cesarean delivery 

Rouse, 2006251 1.8% (427/23579) 

Nisenblat 2006249 3.3% (16/491) 

2 prior cesarean deliveries 

Rouse, 2006251 2.6% (202/7902) 

Macones 2005263 0.54 

(0.23 to 1.27) 

1.18% (2888) 

ERCD versus VBAC 

>2 prior cesarean deliveries 

Nisenblat 2006249 2.3 

(1.1 to 4.5) 

7.9% (22/277) 

101 
 

 

 

 

Table 22. Multiple cesarean deliveries effect on rates of hemorrhage 

Studies 

Adjusted odds ratio 

95% CI or P value N 

3 prior cesarean deliveries 

Rouse, 2006251 4.3% (75/1754) 

4 prior cesarean deliveries 

Rouse, 2006251 4.6% (15/323) 

>5 prior cesarean deliveries 

Rouse, 2006251 7.6 

(4.0 to 14.3) 

14.6%(16/110) 

Abbreviations: CI=confidence interval; ERCD=elective repeat cesarean delivery; VBAC=vaginal birth after 

cesarean 

Adhesions. Three good or fair quality studies discussed the presence of adhesions after 

multiple cesarean deliveries (Table 23).235, 249, 257 Uniform definitions of adhesions were not 

used. Nisenblat et al reported adhesions present in 25.6 percent (124/491) of women undergoing 

their second cesarean delivery versus 46.1 percent (124/277) for women with two or more prior 

cesarean deliveries (odds ratio 2.5; 95 percent CI: 1.8 to 3.4).249 Lynch et al studied outcomes at 

a single hospital in Ireland and found a similar rate of adhesions (48.8 percent) in women with 

two or more prior cesarean deliveries (122/250).257 Women with three or more prior cesarean 

deliveries at the University of Oulu, Finland were studied to identify outcomes in women with 

multiple cesarean deliveries.235 Records were reviewed for 64 women who underwent a total of 

341 cesarean deliveries, 149 of which were their fourth or greater cesarean. These women were 

compared with a control group consisting of the next cesarean in the same situation (elective 

versus emergency). Intraperitoneal adhesions were noted in 18.2 percent of cases versus 2.7 

percent of controls (odds ratio 8.1; 95 percent CI: 2.7 to 23.8). Overall, incidence of adhesions 

appears to increase with increasing numbers of cesareans. 

Table 23. Multiple cesarean deliveries effect on rates of adhesions 

Studies 

Adjusted odds ratio 

95% CI or P value N 

1 prior cesarean delivery 

Nisenblat, 2006249 25.6% 

(124/491) 

>2 prior cesarean deliveries 

Lynch 2003257 48.8% 

(122/250) 

Nisenblat, 2006249 2.5 

p<0.001, (1.8 to 3.4) 

46.1% 

(124/277) 

>3 prior cesarean deliveries 

Juntunen, 2004235 8.1 

0.0001 (2.7 to 23.8) 

18.2% 

(149) 

Abbreviations: CI=confidence interval 

Surgical injury. The data regarding surgical injury and multiple cesarean deliveries is very 

limited and consists of two good quality studies (Table 24).236, 257 Both studies evaluated bladder 

injuries. Lynch et al found 1.6 percent of women with two or more prior cesareans had a bladder 

injury (4/250).257 Silver et al noted less than 0.3 percent of women with less than three prior 

cesareans experienced a bladder injury compared with 4.5 percent of women with five or more 

prior cesareans.236 This trend was statistically significant at p<0.001. Risk of bowel and ureteral 

injury with increasing number of cesareans was also statistically significant, although overall 

102 
incidence was less than 1.2 percent. Bladder, bowel, and ureteral injury are uncommon 

occurrences and appear to increase with multiple cesareans. 

Table 24. Multiple cesarean deliveries effect on rates of surgical injury 

Studies N 

Zero prior cesarean deliveries 

Silver, 2006236 0.13% (8/6201) 

1 prior cesarean delivery 

Silver, 2006236 0.09% (15/15808) 

2 prior cesarean deliveries 

Silver, 2006236 0.28% (18/6324) 

>2 prior cesarean deliveries 

Lynch, 2003257 1.6% (4/250) 

3 prior cesarean deliveries 

Silver, 2006236 1.17% (17/1452) 

4 prior cesarean deliveries 

Silver, 2006236 1.94% (5/258) 

>5 prior cesarean deliveries 

Silver, 2006236 4.49% (4/89) 

Perioperative infection. The data regarding perioperative infection and multiple cesarean 

deliveries is limited and consists of four good or fair quality studies.81, 235, 236, 257 As indicated 

earlier in the report, there was no uniform definition of infection. Phelan et al reported an 

incidence of “febrile morbidity” of 19.2 percent (163/847) for women undergoing RCD, but the 

authors did not define febrile morbidity.81 Similarly, Juntunen et al. noted 14.1 percent of women 

with three or more prior cesareans had postoperative infections (odds ratio 0.9; 95 percent CI: 

0.5 to 1.8), but the criteria for infection were not defined.235 Urinary tract infection (UTI) and 

upper respiratory tract infection (URI) were used by Lynch et al to describe postoperative 

infectious complications (Table 25).257 Silver et al defined postpartum endometritis clinically on 

the absence of findings consistent with an extrauterine source.236 There was a statistically 

significant increase in endometritis with multiple cesareans (p<0.001). Based on these studies, 

the risk of postoperative infection with multiple cesareans remains unclear. 

Table 25. Multiple cesarean deliveries effect on rates of perioperative infection 

Studies N 

Zero prior cesarean deliveries 

Silver, 2006236 Endometritis: 5.98% (371/6,201) 

1 prior cesarean delivery 

Silver, 2006236 2.56% (404/15,808) 

>1 prior cesarean delivery 

Phelan, 198781 "Febrile morbidity": 19.2%(163/847) 

2 prior cesarean deliveries 

Silver, 2006236 2.81% (178/6,324) 

Lynch, 2003257 Urinary tract infection, upper respiratory track infection: 

11.2% (80) 

3 prior cesarean deliveries 

Silver, 2006236 2.96% (43/,1452) 

Lynch, 2003257 10.7% (131) 

103 
Table 25. Multiple cesarean deliveries effect on rates of perioperative infection 

Studies N 

>3 prior cesarean deliveries 

Juntunen, 2004235 "Postoperative infections": 14.1% (149) 

Adjusted odds ratio: 0.9 

95% confidence interval: 0.869 (0.5, 1.8) 

4 prior cesarean deliveries 

Silver, 2006236 1.55% (4/258) 

>4 prior cesarean deliveries 

Lynch, 2003257 23% (39) 

>5 prior cesarean deliveries 

Silver, 2006236 6.74% (6/89) 

p=0.001 

Wound complications. Two good quality studies report incidence of wound complications 

with multiple cesarean deliveries.236, 257 Silver et al reviewed wound infection and wound 

dehiscence and found no statistically significant change with multiple cesareans (p=0.09 and 

0.18, respectively).236 Similarly, Lynch et al. found no correlation between number of cesareans 

and wound problems (Table 26).257 

Table 26. Multiple cesarean deliveries effect on rates of wound complications 

Studies N 

Zero prior cesarean deliveries 

Silver, 2006236 Dehiscence, infection: 1.9% (118/6201) 

1 prior cesarean delivery 

Silver, 2006236 1.05% (165/15808) 

2 prior cesarean deliveries 

Lynch, 2003257 "Problem": 6.2% (80) 

Silver, 2006236 1.69% (107/6324) 

3 prior cesarean deliveries 

Lynch, 2003257 7.6% (131) 

Silver, 2006236 1.52% (22/1452) 

4 prior cesarean deliveries 

Silver, 2006236 4.23% (11/258) 

>4 prior cesarean deliveries 

Lynch, 2003257 5.1% (39) 

5 prior cesarean deliveries 

Silver, 2006236 3.37% (3/89) 

Hysterectomy. Seven good or fair quality studies evaluated the rate of hysterectomy with 

multiple cesarean deliveries (Table 27).81, 236, 249, 252, 254, 257, 260 Women requiring hysterectomy 

due to abnormal placentation were discussed previously in this report (see Abnormal 

Placentation section). There are three population-based, matched case-control studies with 

women requiring peripartum hysterectomy chosen as cases.252, 254, 260 Bodelon et al used the 

Washington State birth certificate registry. Women undergoing their first cesarean delivery were 

more likely to require hysterectomy than were women delivering vaginally (odds ratio 4.6; 95 

percent CI: 3.5 to 6.0). Women with one or more prior cesarean were significantly more likely to 

require hysterectomy (odds ratio 7.9; 95 percent CI: 5.8 to 10.7).252 Knight et al used the United 

Kingdom Obstetric Surveillance System and similarly noted an increased risk for hysterectomy 

104 
 

 

 

 

 

 

 

 

 

 

with primary cesarean (odds ratio 7.13; 95 percent CI: 3.71 to 13.7). The risk of peripartum 

hysterectomy for women with two or more prior cesareans was significantly higher (odds ratio 

18.6; 95 percent CI: 7.67 to 45.4) than for women with one prior cesarean delivery (odds ratio 

2.14; 95 percent CI: 1.37 to 3.33).254 Zelop et al used obstetric records at Brigham and Women’s 

Hospital to perform a case series of emergency peripartum hysterectomies between 1983 and 

1991. Hysterectomy rates for women undergoing a primary cesarean were 0.062 percent, and 

increased with one prior cesarean delivery to 0.735 percent. Women with one or more prior 

cesarean had a hysterectomy rate of 1.08 percent, these rates were statistically significant.260 

Nisenblat et al compared women undergoing a second cesarean versus women with two or more 

prior cesareans. The rate of hysterectomy increased from 0.2 percent (1/491) to 1.1 percent 

(3/277) in the multiple cesarean group, but the result was not statistically significant.249 Lynch et 

al found a similar rate of hysterectomy in women with four or more prior cesareans of 1.1 

percent (2/170).257 Silver et al used MFMU data and noted increasing incidence of hysterectomy 

with increasing number of cesareans from 0.65, 0.42, 0.90, 2.41, 3.49, and 8.99 percent with zero 

to five or more prior cesareans, respectively. Women with five or more prior cesareans were 15 

times more likely to require hysterectomy (odds ratio 15.2; 95 percent CI: 6.9 to 33.5), these 

results were statistically significant.236 These studies strongly support a correlation between 

multiple cesareans and hysterectomy. The odds ratio for hysterectomy with one prior cesarean is 

0.7 to 2.14, with one or more is 1.4 to 7.9, and two or more is 3.8 to 18.6. 

Table 27. Multiple cesarean deliveries effect on rates of hysterectomy 

Studies 

Adjusted odds ratio 

95% Confidence interval or P 

value N Per/1000 

Zero prior cesarean deliveries 

Bodelon, 2009252 4.6 

(3.5 to 6.0) 

Knight, 2008254 7.13 

(3.71 to 13.7) 

Risk 1:1700 (1:1300­

1:2300) 

Silver, 2006236 0.65% 

(40/6201) 

Zelop, 1993260 19/35240 0.62 

1 prior cesarean delivery 

Nisenblat, 2006249 0.2% 

(1/491) 

Knight, 2008254 2.14 

(1.37 to 3.33) 

80 Risk 1:1300 (1:1000­

1:1600) 

Silver, 2006236 0.7 

(0.4 to 0.97) 

Zelop, 1993260 29/4366 7.35 

>1 prior cesarean delivery 

Bodelon, 2009252 7.9 

(5.8 to 10.7) 

Phelan, 198781 1.7% 

(14/847) 

Zelop, 1993260 70/6694 10.75 

2 prior cesarean deliveries 

Silver, 2006236 1.4 

(0.9 to 2.1) 

>2 prior cesarean deliveries 

105 
 

 

 

 

Table 27. Multiple cesarean deliveries effect on rates of hysterectomy 

Studies 

Adjusted odds ratio 

95% Confidence interval or P 

value N Per/1000 

Nisenblat, 2006249 0.136 1.1% 

(3/277) 

Knight, 2008254 18.6 

(7.67 to 45.4) 

84 Risk 1:220 (1:180-1:270) 

3 prior cesarean deliveries 

Silver, 2006236 3.8 

(2.4 to 6.0) 

4 prior cesarean deliveries 

Silver, 2006236 5.6 

(2.7 to 11.6) 

>4 prior cesarean deliveries 

Lynch, 2003257 1.1% 

(2/170) 

>5 prior cesarean deliveries 

Silver, 2006236 15.2 

(6.9 to 33.5) 

Summary of maternal complications associated with multiple cesarean deliveries. Thirtythree percent of births in the U.S. as of 2007 were accomplished via cesarean delivery.1

 Many of 

these women will have additional children in the future and will be faced with the decision 

regarding mode of delivery. If she has a RCD, she will most likely have a cesarean for the 

remainder of her pregnancies. If she has a VBAC, she will likely have additional VBAC and 

avoid multiple cesareans. One of the fundamental gaps in the literature is intention for future 

pregnancies. This report supports prior evidence that although maternal morbidity increases with 

cesarean and neonatal morbidity increases with TOL, the overall incidence is extremely 

uncommon. The overwhelming majority of second pregnancies will result in a healthy mom and 

baby regardless of delivery method. This changes for women with multiple cesareans. As the 

number of prior cesareans increases, the maternal morbidity increases, especially for women 

with more than three prior cesareans. These women are at statistically significant increased risk 

of previa, accreta, and hysterectomy. The highest risk group is women with previa and prior 

cesarean, and the risks increase with increasing number of prior cesarean. Women with three or 

more prior cesareans and previa had a statistically significant increased risk of accreta (3.3 to 4 

percent versus 50 to 67 percent), hysterectomy (0.7 to 4 percent versus 50 to 67 percent), and 

composite maternal morbidity (15 versus 83 percent) compared with women with previa and no 

cesarean. The only identified prevention of previa is avoiding uterine instrumentation. The 

overall incidence of previa is uncommon. The incidence of previa in women with any prior 

cesarean was 1.2 percent and for women with three or more prior cesareans it was 2.8 percent. 

There is no identified method for determining which women will develop previa in a subsequent 

pregnancy. All pregnant women are at risk for previa, women with previa are at increased risk of 

maternal morbidity, the incidence of previa and risk of morbidity increases with increasing 

number of prior cesareans, and there is no ability to predict which women will develop these 

complications. This has substantial implications for VBAC counseling relating to the risks of 

major morbidity associated with multiple cesareans in future pregnancies, especially for women 

desiring large families. Unfortunately, women are often unable to predict how many children 

they will have. Per the CDC 

(http://www.cdc.gov/reproductivehealth/UnintendedPregnancy/index.htm), the unintended 

106 
pregnancy rate in the U.S. in 2001 was approximately 50 percent. Therefore, it is not unlikely 

that women will be facing additional pregnancies following cesarean, even if they were not 

planning to have more children. The inability to determine which women have completed 

childbearing and this report’s conclusion that maternal morbidity increases with multiple 

cesareans supports the ACOG 2004 practice bulletin recommendation that most women with a 

prior cesarean should be counseled about VBAC and offered a TOL. 

Direction of scar. There are three recognized types of uterine incision; the most common 

approach is the low transverse incision through the lower uterine segment. Some surgeons prefer 

the low vertical incision, although concern remains that it may enter the muscular portion of the 

uterus. The classical incision, or high vertical incision, has been strongly associated with 

increased risk of uterine rupture and is a recognized contraindication to labor. Modifications of 

low transverse incisions—which require entering the muscular portion of the uterus, known as 

“T” or “J” incisions—are considered classical incisions for classification purposes. In addition, 

many women are unaware of what type of incision they had with a prior cesarean delivery, 

especially if the delivery was performed in countries other than the U.S. where operative reports 

may not be available. These incisions are classified as unknown. It remains unclear the effect of 

low vertical or unknown incisions on the risk of uterine rupture. 

Impact of direction of scar. The published literature regarding impact of the direction of scar 

is limited and consists of one good and seven fair quality studies (Table 28).80, 84, 175, 203, 233, 264-266 

These studies focus on impact of direction of scar and subsequent uterine rupture. As previously 

defined in this report, complete uterine rupture is a separation through the entire thickness of the 

wall including visceral serosa (with or without extrusion of part of all of fetal-placental unit). An 

incomplete uterine rupture is defined as a separation that was not completely through all layers 

of the uterine wall (e.g., serosa intact). Only one author used these definitions.80 All other studies 

will therefore be listed as “uterine defect” which will encompass both complete and incomplete 

uterine rupture. 

Table 28. Impact of direction of scar 

Studies Uterine Rupture Definition 

Type of 

Scar Mode of Delivery 

Uterine 

Defect Rate 

Landon 2006 80 Dehiscence - disruption of the 

uterine muscle with intact 

serosa. Rupture - disruption or 

tear of the uterine muscle and 

visceral peritoneum 

LVCD TOL: 102 2 (2.0%) 

LTCD TOL: 14,483 105 (0.7%) 

Classical TOL: 105 2 (1.9%) 

Unknown TOL: 3206 15 (0.5%) 

107 
Table 28. Impact of direction of scar 

Studies Uterine Rupture Definition 

Type of 

Scar Mode of Delivery 

Uterine 

Defect Rate 

Paul, 1985 175 Dehiscence - nontraumatic LVCD TOL: 50 0 

separation of the uterine scar 

without bleeding or extrusion 

of the fetus into the wound. 

Rupture - scar separation with 

bleeding, hematoma 

formation, or extrusion of the 

fetus 

LTCD TOL: 701 16 (2.3%) 

Martin, 1983203 Dehiscence - palpable and/or 

visualized uterine defect. 

Rupture - dehiscence that 

LVCD VBAC: 6/12 (50%) 

TOL-CD: 6 

ERCD: 64 

0 

0 

0 

required intervention LTCD VBAC: 95/150 

(64%) 

TOL-CD: 55 

ERCD: 483 

1 (1.1%) 

4 (7.2%) 

6 (1.2%) 

Stovall, 1987 84 Dehiscence - palpable and/or 

visualized defect in the 

previous scar. Rupture - 

LVCD VBAC: 57/64 

(89%) 

TOL-CD: 7 

0 

0 

dehiscence requiring surgical 

intervention or blood 

component. 

LTCD VBAC: 159/208 

(76%) 

TOL-CD: 49 

0 

1 (2.0%) 

Tahilramaney, 

1984266 Dehiscence - silent separation 

of the uterine scar. 

LVCD VBAC: 0 

CD: 11 

0 

1 (9%) 

different #s 

text/table 

Rupture - sudden separation 

of the scar with hemorrhage 

LVCD or 

fundal 

VBAC: 5 

CD: 16 

0 

2 (12%) 

requiring immediate 

intervention. 

LTCD VBAC: 156 

CD: 218 

3 (2.2%) 

7 (3.3%) 

Unknown VBAC: 104 

CD: 347 

0 

11 (3.2%) 

Leung, 1993233 Rupture - symptomatic uterine 

scar separation that required 

LTCD Study of ruptures 

only 

64 

emergency laparotomy. 

Asymptomatic dehiscences 

were excluded. 

LVCD or 

classical 

Study of ruptures 

only 

11 

Unclassified Study of ruptures 

only 

24 

Lin, 2004265 Rupture - uterine scar 

separation associated with 

LVCD 39 0 

abnormal fetal heart rate LTCD 1931 0.60% 

tracing, extrusion of fetal parts, Classical 145 0 

or hemorrhage. Unknown 1312 0.50% 

Grubb, 1996264 Dehiscence - scar separation 

noted incidentally in 

asymptomatic patient. 

Rupture - scar separation with 

either fetal distress or maternal 

complication requiring 

operative intervention. 

Unknown 197 5 (2.5%) 

Abbreviations: LTCD=low transverse cesarean delivery; LVCD=low vertical cesarean delivery; TOL=trial 

of labor; TOL-CD=trial of labor followed by cesarean delivery; VBAC=vaginal birth after cesarean delivery 

108 
Uterine rupture. Landon et al 2006 used the MFMU database to study the risk of uterine 

rupture based on direction of scar for women attempting a TOL.80 For women with a prior LTCD 

in that study, the overall rupture rate was 105/14,483 deliveries (0.7 percent). The rate with a 

prior LVCD was 2.0 percent (2/102 deliveries). There were also two uterine ruptures in 102 

women with prior classical, J, or T incisions who refused cesarean delivery or presented in 

advanced labor, resulting in a rupture rate of 1.9 percent. 

Uterine defect, prior low vertical incision - trial of labor. Three fair quality cohort studies 

reported on prior LVCS and incidence of uterine defects in women undergoing TOL.84, 175, 203 

Paul et al examined 16,200 deliveries, of which 751 women had a prior cesarean delivery and 

attempted a TOL.175 Fifty women had a prior LVCD, and per the authors, there were no serious 

complications. Martin et al studied 717 patients with prior cesarean who were separated into 

groups based on intended mode of delivery.203 For women who elected a TOL, six had a prior 

LVCD with no cases of uterine defects. Ninety-five women with a prior LTCD had VBAC 

deliveries with one uterine defect. Of the 61 women who required abdominal delivery after TOL, 

six had a prior LVCD with no cases of uterine defects, and 55 women had prior LTCD with four 

defects. The authors concluded that the evidence did not support the theory that low-vertical 

incisions are more likely to rupture than LTCD. Stovall et al performed a prospective cohort 

study of 272 women with a prior cesarean attempting a TOL at the University of Tennessee 

College of Medicine.84 One hundred and fifty-nine out of 208 women with a prior LTCD 

underwent VBAC deliveries with one uterine defect. Fifty-seven out of 64 women with a prior 

LVCD underwent VBAC deliveries with no defects. These studies suggest that TOL with a prior 

LVCD does not have an increased rate of uterine dehiscence compared with prior LTCD, but the 

total number of TOL attempts with prior LVCD reported in these three studies is 126. This 

suggests that the sample size may have not been large enough to capture the true risk of uterine 

defect with a prior LVCD, but it is reassuring that there were no cases of uterine defects in this 

series. 

Uterine defect, prior low vertical incision - elective repeat cesarean delivery. Martin et al 

studied 717 patients with a prior cesarean delivery separated into groups based on intended mode 

of delivery.203 Of the participants, 547 chose ERCD, 483 with a prior LTCD and 64 with a prior 

LVCD. There were six uterine defects in the LTCD group and no cases in the LVCD group. 

Uterine defect, prior low vertical incision - unknown intended mode of delivery. Three fair 

quality cohort studies evaluated a prior LVCD and incidence of uterine defect but did not discuss 

intended mode of delivery.233, 265, 266 As the authors did not report which patients attempted TOL, 

it is unclear whether patients with scar disruption presented with asymptomatic defects at the 

time of ERCD or after attempted TOL. Tahilramaney et al reported defects in 2.8 percent of 374 

patients with prior LTCD.266 One hundred and thirty-four women delivered vaginally with 

uterine defects in three versus 211 delivering via cesarean with seven cases of defect. For the 11 

patients with a prior LVCD, all were delivered via cesarean with one defect (9 percent). For the 

21 prior classical or vertical incisions of unknown type, there were five vaginal deliveries 

without complications and two cases of uterine defects with cesarean (14 percent). The authors 

concluded that type of uterine incision was not statistically significant in regards to uterine 

dehiscence. Leung et al reviewed cases of uterine defects at one institution over a 10 year 

period.233 There were 16,467 women who had a prior cesarean with 107 cases of uterine defects, 

99 with complete records. Per patient history, 90 percent of scar types were unknown, but, when 

possible, scars were classified at the time of laparotomy. Eleven were recorded as 

classical/vertical, 64 were transverse, and 24 remained unknown. A database at Emory 

109 
 

University was used by Lin et al to identify patients with a prior cesarean who delivered at 

greater than 28 weeks and to study the impact of the direction of scar and uterine defects.265 Of 

3,533 patients, 145 had a prior classical scar, 1,931 had a LTCD, 39 a LVCD, and 1,312 had an 

unknown scar. There were 106 patients excluded for unidentified scar. There were no cases of 

uterine defects with prior LVCD or classical incisions. 

Uterine defect, unknown uterine scar. Unknown uterine scar remains a diagnostic challenge. 

One good and three fair quality studies evaluated outcomes for women with unknown 

incisions.221, 264, 266 Grubb et al performed a RCT of 197 women in latent labor with unknown 

uterine scars comparing nonintervention to active management.264 In the intervention group, 

there were five cases of uterine defects. There were no cases in the nonintervention group (0 

versus 5 percent, p=0.03). Per the author’s definition, there was one case of rupture and four 

uterine dehiscences. The uterine rupture was through a vertical scar (later called a T incision). 

The four cases of uterine dehiscence were with LVCD, and three were noted on routine 

exploration of the uterine cavity following VBAC. Tahilramaney et al reviewed 451 patients 

with unknown incisions, 93 delivered vaginally with no complications, and 319 delivered via 

cesarean delivery, of which 11 (2.6 percent) experienced uterine defects.266 Lin et al reviewed 

1,312 patients with unknown scar. In comparison to patients with a known prior LTCD, there 

was no increased rate of uterine defects in patients with an unknown scar (0.6 and 0.5 percent, 

respectively).265 Landon et al found that for women with an unknown scar, there were 15 

ruptures in 3,206 deliveries (0.5 percent).221 These studies suggest that women with an unknown 

scar are not at significantly increased risk of uterine dehiscence or rupture with TOL. 

Direction of scar summary. Because the scope of this report started after the NIH conference 

in 1980, data regarding the risk of uterine defect for classical incision is largely absent and what 

is there is likely biased as providers in general will not allow a trial of labor among women with 

prior classical incisions. Studies prior to 1980 suggest that women with prior classical are at 

substantially increased risk for uterine rupture and should not undergo labor. The evidence 

regarding prior LVCD is very limited. Of six studies on 336 women with LVCD, there are two 

reported cases of uterine rupture and one uterine defect. These limited data suggests that women 

with a prior LVCD are not at a significantly increased risk of uterine dehiscence or rupture 

compared with women with a prior LTCD. Women with an unknown scar are not at a 

significantly increased risk of uterine dehiscence or rupture with TOL compared with women 

with prior LTCD. 

Obesity. Because obesity is an increasingly important health problem in the U.S., the impact 

of BMI and/or weight on VBAC rate was investigated. RCT, cohort, or case series studies that 

reported weight or BMI for TOL or ERCD groups for VBAC rate, or maternal or infant 

outcomes were included. Of the 119 full text articles retrieved and assessed for inclusion, seven 

good or fair quality cohort studies were reviewed.78, 110, 126, 135, 240, 267, 268 A number of studies 

provide context for the data related to maternal BMI from the MFMU cohort,80, 221, one 

highlighting health outcomes by BMI and TOL versus ERCD groups will be discussed here.78 

Three studies of poor quality were excluded from analysis.269-271 Most studies stratified BMI in 

predefined categories,78, 110, 126, 267 while others used weight.135, 240, 268 The most commonly used 

definition included four BMI (kg/m2) categories: normal, less than 25; overweight, 25 to 29.9; 

obese, 30 to 39.9; and morbidly obese greater than 40. BMI cutoffs did vary within categories. 

One looked only at women eligible for a TOL who weighed more than 300 pounds.240 

Overall VBAC rates compared by BMI groups will be discussed (Table 29) along with a 

brief overview of TOL maternal and infant outcomes by BMI status (Table 30). The largest of 

110 
 

 

 

 

the U.S. cohorts will be emphasized as it provides a comprehensive look at how morbid obesity 

may affect maternal and infant morbidity, TOL compared with ERCD.78 

Table 29. Vaginal birth after cesarean rate in studies with data by body mass index 

Author/ 

Year 

Overall 

VBAC 

Rate% 

VBAC Rate 

BMI (kg/m2

) Categories 

VBAC 

Rate (%) 

Bujold, 2005267 71.2 a) <25: 636/802; OR Not reported 

b) 25-29.9: 2463/3309 OR 0.81 (0.67-0.98); p=0.03 

c) 30-34.9: 1250/1806 OR 0.66 (0.54-0.80); p<0.01 

d) 35-39.9: 325/584 OR 0.38 (0.30-0.49); p=0.03 

e) > 40 or more: 113/217 OR 0.39 (0.28-0.54); p<0.001 

a) 78 

b) 74 

c) 69 

d) 56 

e) 52 

Carroll, 2003268 68 Weight 

a) <200 lbs 28.7±2.8: 27/33 p <0.01 

b) 200-300 lbs 41.3±5.1: 16/28 OR 3.37, 95% CI 1.06 -10.76 

c) >300 lbs 57.5±7.0: 4/69 

a) 82 

b) 57 

c) 13 

Durnwald, 

2004110 

66 < 19.8 

19.9-24.9 

25-29.9 

>30 comparing b & d p=0.003 

a) 84.7 

b) 70.5 

c) 65.5 

d) 54.6 

Goodall, 

2005126 

79 a) <25: OR 1.00 (reference) p < 0.001 

b) 25-29.9: OR 1.57 (0.96-2.55) 

c) 30-39.9: OR 2.34 (1.47-3.73) 

d) >40: OR 2.65 (1.42-4.96) 

a) 86 

b) 80 

c) 72 

d) 70 

Juhasz, 

2005135 

77 a) <19.8; OR (reference) 

b) 19.8 - 26: OR 0.85 (0.51-1.41); p=.519 

c) 26.1 - 29: OR 0.65 (0.34-1.26); p=.201 

d) > 29: OR 0.53 (0.29-0.98); p=.043 

 [Linear regression: r= -0.182, P <0.001; 

As BMI increases, the VBAC rate decreases] 

> 40 lb weight gain; OR 0.63 (0.42-0.97); p=0.34 

a) 83 

b) 80 

c) 69 

d) 68 

Hibbard, 

200678 

(MFMU) 

73 a) 18.5-24.9: 1140/1344 p <0 .001 

b) 25.0-29.9: 3690/4747 

c) 30-39.9: 4493/6413 

d) >40: 994/1638 

a) 85 

b) 78 

c) 70 

d) 61 

Chauhan, 

2001240 

NA Morbidly obese ≥40.0: 4/30 CI 3.7- 30.7 13% 

* SL/IA versus ERCD 

† Morbid obesity category: 1 prior cesarean delivery (55.3%), >1 prior cesarean delivery (61.2%); elective 

repeat cesarean delivery (68.3%) 

Abbreviations: BMI=body mass index; CI=confidence interval; lbs=pounds; OR=odds ratio; VBAC=vaginal 

birth after cesarean 

Vaginal birth after cesarean rate and body mass index. Overall VBAC rates ranged from 66 

to 79 percent in the included obesity studies.78, 110, 126, 135, 267, 268 When looking at VBAC rate by 

BMI, most studies found a greater percentage of normal weight women achieved VBAC when 

compared with overweight or obese women.78, 110, 126, 135, 267, 268 The three studies reporting 

VBAC based upon BMI of greater than or equal to 40 showed varying VBAC rates: 52.1 

percent,267 61 percent,78 and 70 percent.126 The two smallest U.S. studies that used weight rather 

than BMI showed women over 300 pounds had a 13 percent VBAC rate.240, 268 In a U.S. 

retrospective chart review, linear regression revealed that as BMI increases, the VBAC rate 

decreases (r=-0.182, P=0.001).135 The MFMU study shows a relationship between increasing 

111 
BMI and decreasing VBAC rate where normal BMI women had an 85 percent VBAC rate while 

those categorized as morbidly obese had a 61 percent VBAC rate (p<0.001; Table 29).78 

The MFMU78 enrolled over 28,000 eligible women aiming to better understand BMI and the 

risks of uterine rupture and infant and maternal morbidity associated with a TOL as compared 

with ERCD. BMI was calculated at delivery using weight in kilograms divided by the square of 

the height in meters (kg/m2

). The subanalysis includes term (greater than or equal to 37 weeks 

GA), singleton pregnancy with a prior cesarean delivery and a BMI greater than 18.5kg/m2

 at 

delivery. The description of the cohort reports a significantly higher BMI in the ERCD group 

compared with the TOL group (BMI: 32.1+6.6 versus 33.6+7, p<0.001).78 Health outcomes for 

those with morbid obesity (BMI greater than 20) were compared for TOL and ERCD. 

Outcome data from the MFMU TOL versus ERCD groups provide insight into how morbid 

obesity may contribute to adverse pregnancy outcomes for both mother and infant. Compared 

with the ERCD group, the TOL group had a greater likelihood of hospital stay (odds ratio 1.2; 95 

percent CI: 1.1 to 1.4), endometritis (odds ratio 2.4; 95 percent CI: 1.7 to 3.5), dehiscence (odds 

ratio 2.4; 95 percent CI: 1.0 to 5.4), rupture/dehiscence (odds ratio 5.6; 95 percent CI: 2.7 to 

11.7), composite morbidity (odds ratio 1.2; 95 percent CI: 1.1 to 1.4) composite morbidity 

(excluding stay, odds ratio 1.8; 95 percent CI: 1.5 to 2.6).78 TOL did not have higher risk of 

transfusion, maternal surgical injury, hysterectomy, wound complications, or thromboembolic 

disease. Compared with the ERCD group, the TOL infants were at greater risk for 5 minute 

Apgar scores less than seven (odds ratio 3.1; 95 percent CI: 2.1 to 4.6) and injury (odds ratio 5.1; 

95 percent CI: 1.9 to 13.8), but not 5 minute Apgar score less than three, sepsis, NICU 

admission, or stillbirth/abortion/neonatal death.78 

Health outcomes by body mass index. Table 30 provides a catalog of statistical findings for 

those included obesity studies that provide information on maternal and infant health outcomes 

by BMI or weight status. Data are summarized for between BMI group differences in rates of 

adverse outcomes as reported in full text papers, with statistical significance also provided. 

Maternal health outcomes. Three cohort studies provide information on women experiencing 

uterine rupture or dehiscence between the BMI groups.78, 135, 267 One German cohort study 

(N=8580) found no difference by BMI group for uterine rupture separation,267 while the largest 

MFMU study found no differences when uterine rupture and dehiscence were analyzed alone, 

but when combined, a significantly higher rate in the largest of four BMI groups was found 

(groups/percent 1) 0.9, 2) 1.5, 3) 1.4, 4) 2.1, respectively, p=0.03).78 Another study reported 

uterine rupture rates were higher in the overweight group (3.6 percent) than in the underweight 

(0.6 percent), normal (1.8 percent), and obese (0 percent) groups, (p=0.041); however, when 

controlling for number of layers of closure, this no longer held true (odds ratio 5.08; 95 percent 

CI: 0.53 to 48.79, p=0.159).135 

More overweight and obese women compared with normal weight women had trouble with 

wound healing complications in the included studies. Compared with lower BMI groups, women 

with greater BMI had statistically significantly more wound infection and fever,267 wound 

infection or endometritis,268 or wound complications and endometritis.78 Alternatively, one U.S. 

cohort (N=725) did not find a significant difference between BMI groups for infection.126 While 

no differences in surgical injury rates were reported in the MFMU,78 those women with lower 

BMI had significantly more third and fourth degree lacerations than women with higher BMI in 

another study (p<0.01). Studies reporting hysterectomy data did not find any differences between 

BMI groups.78, 267 In addition, hemorrhage,267 blood loss,268 and transfusion78 showed no BMI 

group differences. The two studies looking at maternal hospital stay found statistically 

112 
 

significantly higher rates of hospital stay with higher BMI.78, 268 The MFMU sub analysis 

showed maternal stay of 4 or more days in the hospital at 30.3 percent in the morbidly obese 

BMI category, versus 9.4 percent, 12 percent, and 18.9 percent, in the other weight categories 

respectively, p<0.001.78 Finally, there was no significant difference in the adverse event 

thromboembolism in BMI groups.78 

Infant health outcomes. Two studies reporting on infant death did not find a statistically 

significant difference between BMI groups.78, 267 The MFMU secondary analysis did note that 

stillbirth/abortion and neonatal death were the highest in the morbid obesity group (BMI greater 

than 40 was 0.5 percent versus 0.2, 0.3, and 0.3, in the other weight categories, respectively, 

p=0.14).78 When comparing with lower BMI categories, neonatal resuscitation with intubation267 

and NICU admission78 were highest in the morbidly obese groups as well (greater than 40 BMI) 

(p=0.03 and p<0.001, respectively). 

GA and birth weight were common outcomes evaluated in all studies with BMI group data; 

however, results were mixed. Two studies showed no effects for GA,135, 268 while two studies 

indicate that younger GA is associated with lower BMI.126, 267 The largest MFMU study found 

older GA in the overweight and obese BMI groups, when compared with the underweight or 

normal BMI groups (p<0.001).78 Similarly, a U.S. university clinic cohort found older GA in 

higher BMI patients, compared with lower BMI patients.126 A similar picture emerges with 

infant weight and maternal BMI, where three large U.S. studies showed infant weights greater 

than 4,000 grams were more likely in the largest BMI categories,126, 135, 267 and two where infant 

weight was higher in high BMI groups.78, 126 In contrast, one study reported no infant weight 

differences in BMI groups.268 

Apgar scores less than seven taken at 1 minute following delivery showed no differences by 

BMI,126, 267 while Apgar less than seven taken at 5 minutes were more likely in the high BMI 

group compared with lower BMI group.267 The MFMU analysis showed 5 minute Apgar scores 

less than or equal to three were not significantly different between BMI groups.78 In addition, 

infant injury and sepsis were similar for all maternal BMI groups.78 

Summary of obesity. Assessing the risks and benefits of VBAC using BMI is a complex 

exercise. Data show that increasing BMI is linked to decreased VBAC, with morbidly obese 

women and their infants being at the highest risk for adverse outcomes. Compared with normal 

weight mothers, data suggest that obese and morbidly obese women are more likely to suffer 

rupture and/or dehiscence, wound infection, and/or increased hospital stay, while their infants 

may experience more injury and greater weights, specifically greater than 4,000 grams. BMI 

categories use different cut offs and patient inclusion and exclusion criteria vary. Comparison 

across studies for VBAC rate and important health outcomes is further complicated by lack of 

consensus on definitions and priorities. Future research in community practice settings with 

reproducible and valid outcome measures could provide more insight in this field. 

113 
Table 30. Summary of findings on maternal and infant health outcomes for trial of labor and body mass index 

Author, Year 

N/ 

Country/GA 

Maternal Outcomes 

BMI Between Group 

Comparisons Finding 

Infant Outcomes 

BMI Between Group 

Comparisons 

Bujold, 8580 UR separation NS Death NS 

2005267 Germany Wound healing S+ Resuscitation S 

Term 

3rd & 4th degree laceration S – GA S 

Hemorrhage NS Weight*** S 

Fever S+ Weight >4000g S 

Hysterectomy NS Apgar <7 NS 

Apgar 5 min, <7 S Apgar 5 min, <4 NS 

Carroll, 2003268 

138 U.S. NR; all 

Maternal hospital stay Endometritis or wound infection Blood loss 

S + S + NS 

GA Weight 

NS NS 

Goodall, 725 Infection NS GA (<41 wks) S 

2005126 U.S. Induction S + GA (>41 wks) S 

>36 wks Weight <3500g S 

Weight 3500-3999g** S Weight >4000g Apgar, 1 minute <7 S Apgar, 5 minute NS 

NS 

Juhasz, 2005135 

709 U.S. >36 wks 

UR/layers of closure* One-layer closure Pregnancy complications 

S + / NS NS S + 

GA Weight*** Weight > 4000g 

NS S NS 

Hibbard, 14,142 TOL UR NS Stillbirth/abortion/neonatal NS

200678 14,304 Dehiscence NS death @ 

NICHHD ERCD UR/dehiscence combined S + NICU admission S+ 

MFMUN U.S. Surgical injury NS GA $$ S 

>37 wks Wound complications S + Weight & S+ 

Endometritis S + Apgar 5 min, < 7 S 

Transfusion NS Apgar 5 min, < 3 NS 

Maternal hospital stay S + Injury NS 

Hysterectomy NS Sepsis NS 

Thromboembolism NS 
Table 30. Summary of findings on maternal and infant health outcomes for trial of labor and body mass index 

Author, Year 

N/ 

Country/GA 

Maternal Outcomes 

BMI Between Group 

Comparisons Finding 

Infant Outcomes 

BMI Between Group 

Comparisons 

Chauhan, 2001240 

69 U.S. NR; all 

Endometritis Wound infection Pfannensteil skin incision Maternal hospital stay Operating room time 

S 30 percent S 23 percent S 46 percent NS 5.4 +/-3.4 NS 61 +/- 21 

Cord pH NS 

Statistical significance key: 

NS= not significant S+ = significant (greater adverse outcome in higher or highest BMI category)
 S - = significant (less adverse outcome in higher or highest BMI category)
 S = direction or association not clear, additional interpretation needed. * 4 BMI categories; UR greatest in 3rd category, overweight (BMI 26.1-29); when controlling for number of layers of closure associated with UR), it became NS ** 4 BMI categories; weight greatest in 3rd category, obese (BMI 30-39.9): OR 2.34 (1.47-3.73)
 *** greater infant weight in higher BMI categories @ 4 BMI categories; greatest in 4th category, morbidly obese (BMI >40); (0.5 percent vs. 0.2, 0.3, and 0.3 in other 3 catego& 4 BMI categories; increasing from category 1, greatest in 4th category, morbidly obese (BMI >40) $$ 4 BMI categories; older GA in 3rd and 4th obesity category, compared with 1st and 2nd: GA data: a) 18.5-24.9: 39.3 +/- 1.2; b) 25.0-29.9: 39.5 +/- 1.2; c) 30-39.9: 39.7 +/- 1/2; d) >40: 39.7 +/- 1/3 p < .001 Abbreviations: BMI=body mass index; GA=gestational age; NA=not applicable; NR=not reported; UR=uterine rupture; U.S.wk(s)=week(s);
 
Effects of management of trial of labor using a protocol on maternal outcomes. In a 

small cohort study examining the impact of using a strict protocol for managing a trial of labor in 

841 women with prior cesarean delivery compared with 467 women undergoing ERCD maternal 

harms were evaluated.91 The rate of major complications (uterine rupture, hysterectomy, 

relaparotomy, operative injury, or greater than two units of blood transfused) was not statistically 

significantly different between the TOL and ERCD groups (1.8 versus 1.3 percent, p=0.50). 

Adhesions 

One concerning complication from multiple cesarean deliveries is increased complications 

from adhesive disease. This may result in a more difficult RCD, increased postoperative 

complications, or increased complications with future gynecological surgeries. Studies looking at 

adhesions are limited. One study described increased adhesions with increased number of 

cesarean deliveries at the time of cesarean.235 Another study found increased perioperative 

complications with vaginal hysterectomy to be associated with women who underwent one or 

more cesarean in the past (frequency 18.31 versus 3.58 percent, p<0.0001). Specifically, in 

women with a history of cesarean, there was a 5.63 percent rate of bladder injuries compared 

with 0.89 percent in women without cesarean delivery (p= 0.01). A history of cesarean was also 

associated with increased need for adhesiolysis, intestinal injuries, and longer operating time, but 

none of these factors were significant. This study did not delineate one versus multiple cesareans, 

however, and did not evaluate patients with a history of VBAC.272 

A similar study evaluating factors relating to complications during hysterectomy found a 

history of cesarean delivery to be significantly associated with an increase in complications. 

Again, however, this study did not evaluate multiple cesareans or VBAC separately.273 Another 

study evaluated the benefit of closing the peritoneum at the time of initial cesarean to decrease 

the incidence of adhesions in future cesareans. This study found a statistically significant 

increase in the number of patients with severe adhesive disease in those without peritoneal 

closure compared with those who had closure at the time of RCD. (6 versus 42 percent, p=0.003) 

This study did not report the rate of severe adhesions in those patients undergoing multiple 

RCDs; however it does provide evidence that even one cesarean can result in significant 

adhesions. The presence of adhesions can result in complications with subsequent cesareans.274 

This finding was supported by a Canadian study evaluating the presence of adhesions in 

subsequent cesarean. This study found a dose dependent relationship with the prevalence of 

adhesions with the number of cesareans, from 0 percent at primary cesarean delivery to 47.9 

percent at the fourth cesarean.275 In addition, this study found a statistical increase in both 

delivery time as well as total operative time for deliveries complicated by adhesions compared 

with those without adhesions. Operative and delivery times did not increase however with 

increasing number of cesareans.275 

One study evaluating the incidence of postoperative small bowel obstruction, thought to be 

associated with increased adhesive disease, found a smaller rate of obstruction in the cesarean 

delivery group than among those with hysterectomy, adenexal surgery, or myomectomy (0.05 

percent versus 1.63, 0.87, and 0.39 percent; p<0.001).276 

Reproductive Health 

Several studies have attempted to define the impact of cesarean delivery on overall 

reproductive health. One of the important factors emphasized by clinicians is the ultimate family 

116 
plan of patients, due to the increased risk perceived with multiple cesareans. However, there is 

also a concern for impaired fertility due to surgery on the uterus. However, this is not well 

studied with only two studies evaluating impaired fertility. One study of fair quality looking at 

future pregnancies after vaginal delivery, operative vaginal delivery, and cesarean found there to 

be a statistically significant difference in the ability to conceive in subjects undergoing a 

cesarean compared with those who underwent an instrumented vaginal delivery (odds ratio 0.33; 

95 percent CI: 0.12 to 0.98). This study however, did not distinguish between VBAC and 

primary deliveries in the cohort.277 The second study of fair quality found a history of cesarean 

associated with an increased odds of taking greater than one year to conceive after adjusting for 

confounders including maternal and paternal age, demographics, and BMI (odds ratio 1.53; 95 

percent CI: 1.09 to 2.14). Though this study did not evaluate VBAC or multiple cesareans 

separately, there was an increased risk of delayed fertility with increasing parity, suggesting a 

continued effect of at least one cesarean (odds ratio 2.97; 95 percent CI: 1.72 to 5.10).278 

One case-control study found an increased odds ratio of multiple cesarean deliveries (greater 

than or equal to two priors) compared with no pelvic surgery in women with early menopause 

(odds ratio 2.69; 95 percent CI: 1.16 to 6.22) This study however, did not evaluate VBAC and 

this association was not evaluated in a multivariate model.279 No studies evaluated TOL and/or 

RCD with respect to pelvic pain, risk of ectopic pregnancy, and general health risks, such as 

diabetes or high blood pressure. 

What are the short- and long-term benefits and harms to the 

baby of maternal attempt at trial of labor after prior cesarean 

versus elective repeat cesarean delivery, and what factors 

influence benefits and harms? 

This section reviews the infant benefits and harms associated with VBAC compared with 

ERCD. The goal of this endeavor is not only to describe the current knowledge of risks of each 

type of delivery, but to highlight important gaps in the literature. As part of this report, the 

following outcomes were examined: perinatal mortality, respiratory conditions, hypoxic 

ischemic encephalopathy (HIE)/Asphyxia, Sepsis, Birth Trauma, Apgar scores, NICU 

admissions, and breastfeeding. In addition factors that may modify the outcomes associated with 

mode of delivery such as induction of labor, fetal macrosomia and fetal presentation are also 

discussed. 

Perinatal and fetal mortality studies were open to all gestational ages but excluded studies 

that did not specifically exclude infants with known congenital or lethal anomalies. 

Perinatal Mortality 

The definitions accepted by the National Center for Vital Statistics63 were used to review and 

describe the data relating to perinatal mortality and the subsets of fetal and neonatal mortality in 

women with a prior cesarean delivery. The definition of perinatal mortality (perinatal II) 

included infants less than 28 days of age and fetal deaths of 20 weeks or more gestation. To 

study the frequency of stillbirth (antepartum and intrapartum) we used both the intermediate (20 

to 27 weeks gestation) and late (28 weeks or greater gestation) fetal definitions of fetal death in 

an attempt to capture the most studies and allow comparisons to national statistics for the general 

population. Studies that reported fetal loss less than 20 weeks gestation or less than 500 grams 

were not included in the review. Neonatal (infant) mortality was defined as death in the first 28 

117 
 

 

 

days of life.63 . To reduce the effects of prematurity on the neonatal mortality rate, we limited our 

analyses of neonatal mortality to term infants. Two studies,280, 281 which focused specifically on 

the risk of a stillbirth in a subsequent pregnancy after prior cesarean delivery (irrespective of 

mode of delivery in the next pregnancy), were included and are discussed in the section of longterm outcomes and the impact of the mode of delivery on subsequent pregnancies. Eight cohort 

studies of good or fair quality and reporting data on mortality using at least one of these 

definitions of mortality are included.79, 93, 103, 204, 228, 282-284 

Perinatal morality rate. The U.S. perinatal mortality rate (PMR) for infants 28 weeks 

gestation to less than 7 days of life was reported to be 0.66 percent for the year 2005, but notably 

does not exclude infants with congenital anomalies.63 Five good or fair quality cohort studies, 

involving 76,899 infants reported perinatal mortality associated with TOL and ERCD (Table 

31).103, 204, 228, 282, 284 The definition of perinatal mortality among the five studies included fetal 

and neonatal deaths up to 28 days of life. Perinatal mortality was also used to categorize studies 

if it was unclear if the death occurred during labor or after delivery.284 All five studies focused 

exclusively on women delivering at term. Three of the studies occurred in tertiary or university 

settings204, 228, 284 and two utilized population databases.103, 282 

There were 72 perinatal deaths/41,213 births in women having a TOL. The combined PMR 

for women undergoing a TOL was 0.13 percent (95 percent CI: 0.06 to 0.3 percent), translating 

to 1.3 per 1,000 (95 percent CI: 0.6 to 3 per 1,000). There were 46 perinatal deaths/35,686 births 

for women undergoing an ERCD. The combined PMR for ERCD was 0.05 percent (95 percent 

CI: 0.007 to 0.38 percent) this translates to 0.5 per 1,000 (95 percent CI: 0.07 to 3.8 per 1,000 

(Figure 27)). The risk of perinatal mortality was significantly higher for TOL as compared with 

ERCD (RR 1.82; 95 percent CI: 1.24 to 2.67; p=0.041). Using 0.05 percent as the baseline risk 

for ERCD, the calculated risk difference was 0.41 percent (95 percent CI: 0.012 to 0.08 percent) 

which is equivalent to .41 more deaths among women who attempt TOL. One study204 examined 

the influence of labor and underlying maternal medical complications (indications) upon 

perinatal mortality. The PMR was higher among women with underlying medical conditions 

(indications) with and without labor compared with women without indications. Interestingly, 

the impact of labor upon perinatal mortality appeared to differ based upon indication status with 

PMR being higher among the labor group for women without indications (0.22 percent labored 

versus 0.12 percent no labor) and lower for the labor group for women without indications (0.19 

percent labor versus 0.34 percent no labor).204 

118 
Table 31. Perinatal mortality rate (20 weeks or greater gestation to 7 days of life) among any gestational age studie

Number of Perinatal D

Study, Year Study Description 

Years of 

Study N Comparison PMR* TOL PMR* IRCD 

Bujold, 2005282 Retrospective cohort, 

Perinatal Database, Germany 

1991­1997 

8580 Term infants 

TOL versus ERCD 

4/6,718 (0.6/1,000) 0.06% 

 

Richardson, 2005284 Retrospective cohort 

Administrative database; 1 tertiary hospital in Canada 

1992­2002 

3,489 Term infants 

TOL versus no labor 

3/2,646 (1.1/1,000) 0.11% 

 

Sibony, 2006228 Retrospective cohort; University 

hospital France 

1996­2003 

1190 Term infants 

TOL versus ERCD 

1/1,015 (0.9/1,000) 0.10% 

Smith, 2002103 Population-based retrospective cohort 

Administrative Database Scotland 

1992­1997 

24,529 Term infants 

TOL versus ERCD 

20/15,515 (1.3/1,000) 0.13% 

 

Spong, 2007204 Prospective cohort, MFMU Network 1999­ 2002 39,111 Term 

infants 

TOL versus ERCD with labor TOL versus ERCD (without labor) 

44/15,319 (2.9/1,000) 0.29% 

Labor: 2/1,077 (1.9/1,000) 0.19% No labor: 17/5,002 (3.4/1,000) 0.34% 

*Number of deaths per 1,000 Abbreviations: ERCD=elective repeat cesarean delivery; IRCD=indicated repeat cesarean delivery; PMR=perinatal mortalit

labor 
Elective repeat cesarean delivery 

Deaths Total 

•95% confidence intervals are exact 

Smith, 2002 20 15,515 

Bujold, 2005 4 6,718 

Richardson, 2005 3 2,646 

Sibony, 2006 1 1,015 

Spong, 2007 44 15,319 

Smith, 2002 1 9,014 Bujold, 2005 2 1,862 

Richardson, 2005 0 843 

Sibony, 2006 0 175 Spong, 2007 43 23,792 

Com bined (Test for heterogeneity is based on Fisher’s exact text P=0.001) Com bined (Test for heterogeneity is based on Fisher’s exact text P<0.001) 

0.000 0.002 0.004 0.006 0.008 

Death rate (95% confidence interval) 

0.00120.00060.00110.00090.00280.00130.00010.00100 (0, 00 (0, 00.00180.0005

Figure 27. Perinatal mortality rate for trial of labor versus elective repeat cesarean delivery among all studies 

Trial of labor N N Death Rate (95
Fetal mortality rate. The fetal mortality rate (FMR; 20 weeks gestation to birth) in the U.S. 

for the year 2005 was 0.622 percent of live births, leveling off in 2004 (0.620 percent of live 

births) after two decades of decline from a rate of 0.783 percent of live births.63 To understand 

the relationship of a prior cesarean delivery on fetal mortality (antepartum and intrapartum 

death) in women who undergo a TOL versus an ERCD, two good quality studies of women at 

term103, 204 met the inclusion criteria and were reviewed. One study used a retrospective cohort 

from an administrative database,103 while the other used a prospective cohort design.204 The 

studies also differed in that one study103 excluded fetal death prior to the onset of labor. Neither 

study limited their analyses by number or direction of uterine scar. Overall, the FMR was low in 

women attempting a TOL in both studies. When comparing only intrapartum stillbirth, the rates 

of intrapartum fetal demise (IUFD) ranged from 0.01 to 0.04 percent of live births in women 

attempting a TOL to 0 to 0.004 percent for women having an ERCD. Additionally, Spong (2007) 

measured antepartum stillbirth and found a rate of 0.21 percent in women undergoing a TOL 

versus 0.1 percent in women having an ERCD (Table 32).204 

121 
Table 32. Fetal mortality rate (20 weeks or greater gestation and before birth) among term studies 

Number of Fetal Deaths 

Study, Year 

Study 

Description 

Years of 

Study N Comparison FMR* TOL FMR* IRCD FMR* ERCD 

Smith, Population­ 1992­ 24,529 TOL versus Intrapartum Intrapartum 2002103 based 1997 (Intra- ERCD only stillbirth: stillbirth only: 

retrospective partum 7/15,515 0/9,014 

cohort data (0.5/1,000) (0/1000) Administrative only) 0.04% 

Database Term Scotland infants 

Spong, Prospective 1999­ 39,111 1. TOL Antepartum/ Labor: 1.3/2,721 

2007204 cohort, MFMU 2002 Term versus ERCD Intrapartum: 1.1/1,077 (1.1/1,000) 

Network infants with labor 32/15,319 (1.8/1,000) 0.05% 

2. TOL (2.3/1,000) 0.10% 

versus ERCD 0.21% No labor: 212/14,992 

(without Intrapartum- 2.7/5,002 (0.8/1,000) 

labor) only: 

2/15,319 (0.13/1,000) 0.01% 

(1.3/1,000) 0.05% 

1.4% 

*Number of deaths per 1,000 Abbreviations: ERCD=elective repeat cesarean delivery; FMR=fetal mortality rate; IRCD=indicated repeat cesarean deliver

Fetal Medicine Units Network; TOL=trial of labor 
Neonatal morality rate. Six good or fair quality cohort studies reported on the neonatal 

mortality rate (NMR) in women undergoing a TOL versus an ERCD (Table 33).79, 93, 103, 204, 228, 

283 There was a wide range of hospital settings among the six studies, with two studies 

representative of academic medical centers,204, 228 two studies representative of population 

databases,92, 103 and two studies representative of a diversity of hospital types.79, 283 Overall, the 

neonatal mortality rate for TOL was low with a total of 51 neonatal deaths in a total of 44,485 

subjects, for a combined NMR of 0.11 percent (95 percent CI: 0.06 to 0.2 percent). A total of 40 

neonatal deaths occurred in 63,843 women who had either an IRCD or ERCD for a combined 

NMR of 0.6 percent (95 percent CI: 0.02 to 0.15 percent) in the cesarean delivery group (Figure 

28). The risk of neonatal mortality was significantly higher for TOL compared with ERCD with 

a calculated risk difference of 0.058 percent (95 percent CI 0.019 to 0.117 percent), which is 

equivalent to .58 additional perinatal deaths per 1,000 for TOL. 

Two studies provided insight into classifications of patients who appeared to have higher 

NMRs when compared with subgroups.93, 204 In women who were classified as having high-risk 

conditions,93 the NMR in the TOL group was 0.38 percent compared with women without highrisk maternal conditions undergoing a TOL (0.13 percent) and women undergoing ERCD (highrisk women: 0.1 percent NMR; no high-risk condition: 0.05 percent NMR). In another study 

representing the MFMU cohort, Spong et al classified cesarean delivery by IRCD (labor versus 

no labor) and ERCD (labor versus no labor). In this individual study, the NMR was highest in 

the IRCD (no labor) at 0.2 percent.204 Overall, there was no difference in the TOL NMR (0.08 

percent) versus overall cesarean delivery group NMR (0.08 percent). 

While overall rates of perinatal mortality are lower in the reviewed studies in comparison 

with U.S. data for the general population, a noticeable pattern is the association between country 

of origin and perinatal death. The three studies conducted in the U.S. 79, 93, 204 reported higher 

perinatal, fetal, and neonatal mortality, particularly among TOL patients, compared with studies 

conducted outside of the U.S. The U.S. does have a higher infant mortality rate compared with 

either the United Kingdom or Canada (0.626 percent, 0.504 percent and 0.485 percent, 

respectively).285 The studies do not consistently provide details about demographic, societal, or 

health systems issues to explore the potential contributors. 

123 
Table 33. Neonatal mortality rate (death occurring in the first 28 days of life) among term studies 

Number of Neonatal Deaths 

Study, Year 

Study 

Description 

Years of 

Study N Comparison NMR* TOL NMR* IRCD 

Gregory, 200893 Population-based, retrospective 

cohort Administrative Database, CA state, U.S. 

2002 41,450 

Term infants 

TOL versus ERCD High-risk condition No high-risk condition 

TOL any high-risk condition; 12/3,188 (3.8/1,000) 0.38% TOL no high-risk condition: 11/8,292 (1.3/1,000) 0.13% All TOL: 23/11,480 (2/1,000) 0.20% 

ERco(1/0.1ERco10(00.0Al19(00.0

Hook, 199779 Prospective cohort of 3 U.S. hospitals 

in Ohio, U.S. (levels 1,2,3; teaching) 

1992-1993 989 

Term infants 

TOL versus ERCD 

1/492 (2/1,000) 0.20% 

 0/4

Paterson, 1991283 Retrospective cohort of 17 

hospitals Administrative database for NW Thames, UK 

1988 1,059 

Term infants 

TOL versus ERCD 

1/664 (1.5/1000) 0.15% 

 0/3

Sibony, 2006228 Retrospective cohort; University 

hospital France 

1996-2003 1190 TOL versus 

ERCD 

1/1,015 (0.9/1,000) 0.09% 

0/1

Smith, 2002103 Population-based retrospective 

cohort Administrative Database Scotland 

1992-1997 24,529 TOL versus 

ERCD 

13/15,515 (0.8/1,000) 0.08% 

 1/9

0.0
Table 33. Neonatal mortality rate (death occurring in the first 28 days of life) among term studies 

Number of Neonatal Deaths 

Study, Year 

Study 

Description 

Years of 

Study N Comparison NMR* TOL NMR* IRCD 

Spong, 2007204 Prospective cohort, MFMU 

Network 

1999-2002 39,111 TOL versus 

ERCD 1.With labor 2.Without labor 

12/15,319 (0.8/1,000) 0.08% 

1.1/1,077 (0.9/1,000) 0.09% 2.10/5,002 (2/1,000) 0.2% 

3/20.16/1(00.0To(00.0

*Number of deaths per 1,000 Abbreviations: CA=California; CD=cesarean delivery; ERCD=elective repeat cesarean delivery; IRCD=indicated repeat cesareaMFMU=maternal-Fetal Medicine Units Network; NMR=neonatal mortality rate; TOL=trial of labor; NW=Northwest; UK=United K

States 
Figure 28. Neonatal mortality rate for trial of labor versus elective repeat cesarean delivery among term studies 

Trial of labor Elective repeat cesarean delivery 

N 

Deaths 

N 

Total 

Death Rate (95% Confidence 

0.000 0.002 0.004 0.006 0.008 

Death rate (95% confidence interval) 

*95% confidence intervals are exact Paterson, 1991 1 664 Hook, 1997 1 492 Smith, 2002 1 15515 Sibony, 2006 13 1015 Spong, 2007 12 15319 Gregory, 2008 23 11480 Paterson, 1991 0 395 

Hook, 1997 0 497 Smith, 2002 1 9014 Sibony, 2006 0 175 Spong, 2007 20 23792 Gregory, 2008 19 29970 

Combined (Test for heterogeneity is based on Fisher’s exact text P=0.037) Combined (Test for heterogeneity is based on Fisher’s exact text P=0.218) 

0.00150 (0.00004, 0.0080.00203 (0.00005, 0.0110.00084 (0.00045, 0.0010.00099 (0.00002, 0.0050.00078 (0.00040, 0.0010.00200 (0.00127, 0.0030.00114 (0.00063, 0.0020 (0, 0.00930) 0 (0, 0.00740) 0.00011 (0.000003, 0.000 (0, 0.02086) 0.00084 (0.00051, 0.0010.00063 (0.00038, 0.0000.00055 (0.00020, 0.001
Summary and strength of the evidence on perinatal death. Overall, the strength of evidence 

on perinatal mortality was low to moderate. The perinatal, fetal, and neonatal mortality rates 

reported were low, especially when compared with U.S. perinatal statistics from the CDC. 

However, CDC perinatal mortality data do not exclude congenital anomalies. While overall, 

perinatal, fetal, and neonatal mortality rates are low in women with a history of prior cesarean 

delivery, the death rates are significantly higher in women who attempt a TOL versus ERCD. 

Women with high-risk conditions and IRCD appear to have higher rates of neonatal mortality. 

Infant Morbidity 

Because of the association between infant outcomes and prematurity, studies of neonatal 

morbidity were limited to term neonates and included 11 studies of good or fair quality.79, 80, 90, 93, 

97, 103, 156, 204, 283, 284, 286 

Respiratory conditions. Respiratory disorders in newborns are common and account for the 

majority of admissions to the neonatal intensive care unit (NICU) in the immediate newborn 

period.287 While generally considered an intermediate outcome, the need and level of required 

respiratory support at birth is an outcome of clinical, parental, and economic interest. Respiratory 

morbidity can occur regardless of mode of delivery, making conclusions about the relationship to 

the method of labor and delivery unclear. Determining which respiratory indicators are most 

representative of morbidity as well as disagreement about the definitions creates further 

challenges. 

While respiratory distress syndrome (RDS) is primarily a disease of prematurity, term 

neonates can experience respiratory issues at or immediately following birth. Comparisons of 

studies are challenged by: (a) lack of standardized or mutual agreement on definitions of 

respiratory conditions; (b) lack of clarity regarding the importance and clinical significance of 

measures; (c) differences in birth settings; and (d) experience and skill level of available 

providers and staff. It is also worthwhile to note that significant practice changes have occurred 

over the course of the past several decades (e.g., the revised approaches to suctioning of an infant 

with meconium-stained amniotic fluid). These changes make it difficult to draw meaningful 

conclusions about measurements such as the presence of a pediatrician at delivery or the 

frequency of intubation for meconium without specific information about the measurement, 

context, and terminal measure of intermediate variables. 

Six term fair quality cohort studies79, 90, 93, 97, 284, 286 reported an array of respiratory symptoms 

and interventions in the neonates of women who underwent TOL after cesarean delivery versus 

ERCD. Several studies made direct comparisons challenging in that the authors grouped 

respiratory symptoms or disorders together.90, 93, 97 Studies that measured the frequency of 

transient tachypnea of the newborn (TTN), bag-and-mask ventilation, intubation for meconium 

and ventilation in infants born after a TOL versus ERCD are found in Table 34. 

127 
Table 34. Comparison of cohort studies reporting respiratory morbidity in infants among 

term studies 

Study, year Setting TOL/ERCD Measure Findings Significance 

Fisler, University TOL TTN TOL: 8.1% p=0.10 

200390 hospital (N=313) ERCD: 4.5% 

ERCD 

(N=136) Bag-and-mask TOL: 5.8% p=0.10 

ventilation ERCD: 2.2% 

Intubation for TOL: 11.5% p≤0.001 

meconium ERCD: 1.5% 

Hook, Hospital TOL TTN TOL: 3% p<0.05 

199779 levels 1, 2, 3 (N=492) 

ERCD 

ERCD: 6% 

(N=497) Bag-and-mask TOL: 7% p≤0.001 

ventilation ERCD: 2% 

Intubation for TOL: 11.5% p≤0.001 

meconium ERCD: 1.5% 

Intubation for TOL: 2% p≤0.001 

ventilation ERCD: 0.4% 

Meconium TOL: 1% 

aspiration 

syndrome 

ERCD: 0.2% Not 

significant 

Kamath, University TOL Bag-and-mask TOL: 3.34% Not reported 

2009286 Hospital (N=329) 

ERCD 

ventilation ERCD: 2.33% 

(N=343) Intubation TOL: 2.43% Not reported 

(3.labor/4.n 

o labor) 

(reason 

unspecified) 

ERCD: 0.583% 

Richardson, Tertiary care TOL TTN TOL: 1.3% p<0.02 

2005284 facility (N=2646) 

ERCD (no 

labor) 

(N=843) 

ERCD: 2.4% 

Abbreviations: ERCD=elective repeat cesarean delivery; TOL=trial of labor; TTN=transient tachypnea of 

the newborn 

Three studies79, 90, 286 compared the frequency of bag-and-mask ventilation in the infant when 

women underwent TOL versus ERCD (Figure 29). The summary estimate of rates for infants 

needing bag-and-mask ventilation for TOL was 5.4 percent (95 percent CI: 3.5 to 7.6 percent) 

while the rate for ERCD was 2.5 percent (95 percent CI: 1.6 to 3.6 percent). Infants in the TOL 

group were significantly more likely to receive bag-and-mask ventilation with a pooled RD for 

TOL versus ERCD of 2.5 percent (95 percent CI: 0.72 to 5.0 percent.). The I

2

 statistic for 

heterogeneity was 42.9 percent (between study heterogeneity accounts for 42.9 percent of the 

total heterogeneity). The Q-statistic for heterogeneity was 3.5 (p=0.1736). 

128 
Figure 29. Need for bag-and-mask resuscitation among term studies 

Study Name N

Fisler, 2003 449 

Hook, 1997 989 

Kamath, 2009 672 

Three studies reported rates of TTN (Figure 30).79, 90, 284 There was significant heterogeneity 

among the three studies with a Q-statistic of 6.05 p=0.0485 and I

2

 of 67 percent (indicating the 

between-study heterogeneity accounts for 67 percent of the total heterogeneity). The pooled 

absolute risk for TTN in the TOL group was 3.6 percent (95 percent CI: 0.9 to 8.0 percent) and 

4.2 percent (95 percent CI: 1.9 to 7.3 percent) for ERCD. There was no statistically significant 

difference between the risk in the two groups using a random effects model with a pooled RD of 

-0.83 percent (95 percent CI: -3.35 to 1.7 percent) for TOL versus ERCD. 

129 
Study Name N Study Name 

Fisler, 2003 

Hook, 1997 

Richardson, 2004 

449 

989 

3489 

N 

 

Figure 30. Rates of transient tachypnea of the newborn for trial of labor versus elective repeat 

cesarean delivery among term studies 

Only two studies79, 90 measured respiratory care of the infant with meconium-stained 

amniotic fluid. While one study90 measured intubation for meconium, Hook et al79 measured 

meconium aspiration syndrome. Both studies found respiratory care due to meconium-stained 

amniotic fluid to be greater in infants undergoing a TOL versus ERCD (Table 34). 

One study examined respiratory morbidity occurring in infants born by planned and actual 

route of delivery (e.g., ERCD with and without labor, VBAC, and TOL resulting in RCD).286 

This study found infants born after a TOL resulting in CD required the most bag-and-mask 

ventilation and intubation, while infants born by ERCD ( with our without no labor) required the 

most oxygen therapy (blow-by oxygen, continuous positive airway pressure).286 

Ultimately, there were very few studies that reported on respiratory outcomes for term infants 

born by VBAC or ERCD. While infants born after a TOL were more likely to require bag-andmask ventilation compared with infants born by ERCD, other respiratory outcomes revealed no 

differences between routes of delivery. The fact that there are so few studies that measure 

respiratory outcomes for term infants is an important issue as respiratory outcomes are very 

important to clinicians and patients. 

Summary and strength of the evidence on infant respiratory morbidity. The strength of 

evidence on the respiratory morbidity of the infant for VBAC versus ERCD was low due to lack 

of precision in estimates and inconsistency in findings. Respiratory distress syndrome was not 

included in this review of the literature because RDS is primarily a disease of prematurity and 

130 
neonatal outcomes were primarily focused on term neonates to reduce the confounding by 

prematurity. Studies were conflicting regarding whether VBAC or ERCD resulted in more TTN. 

Two studies found significantly more infants required intubation for meconium in infants 

undergoing TOL versus ERCD. is a general lack of consensus among studies regarding what 

types of respiratory indicators are most representative of health or morbidity. 

Hypoxic-ischemic encephalopathy/asphyxia. Hypoxic ischemic encephalopathy (HIE), 

neonatal encephalopathy, asphyxia, perinatal asphyxia, and hypoxia are terms used in the 

literature to describe a potentially serious neonatal complications. These descriptors attempt to 

link a hypoxic event during birth to intermediate and/or long-term neonatal outcomes. Several 

challenges exist in trying to capture the frequency and severity of such an outcome including 

lack of agreement regarding definition, timing, and measurement. Proposed criteria to define an 

acute intrapartum hypoxic event as sufficient to cause a long-term outcome such as cerebral 

palsy have been advanced by ACOG and the International Cerebral Palsy Task Force.288 The 

presence of four essential criteria have been proposed in order to link an intrapartum hypoxicischemic insult causing a moderate to severe neonatal encephalopathy resulting in cerebral palsy: 

1) evidence of metabolic acidosis in fetal umbilical cord arterial blood obtained at delivery (pH 

less than 7 and base deficit of 12 mmol/L or more), 2) early onset of severe or moderate neonatal 

encephalopathy in infants born at 34 or more weeks' gestation, 3) cerebral palsy of the spastic 

quadriplegic or dyskinetic type, and 4) exclusion of other identifiable etiologies, such as trauma, 

coagulation disorders, infectious conditions, or genetic disorders.288 

Three fair quality cohort studies attempted to measure this phenomenon in some manner.80, 93, 

284 Gregory et al, in a large, population-based study, measured the frequency of hypoxia (by 

ICD-9 codes) in high- and low-risk women who underwent TOL and ERCD at term.93 High-risk 

antepartum conditions contributing to neonatal hypoxia in women with a prior cesarean delivery 

were antepartum bleeding (odds ratio 2.9; 95 percent CI: 1.3 to 6.6) and oligohydramnios (odds 

ratio 2.5; 95 percent CI: 1.1 to 5.7). Overall, there was little difference in the frequency of 

hypoxic events (defined by ICD 9 category codes 768.0,1,2,3,4,5,6,9) in infants born to mothers 

with no high-risk clinical condition (TOL: 0.89 percent, ERCD: 0.32 percent) versus infants 

whose mothers had any number of high-risk clinical conditions (TOL: 1.29 percent versus 

ERCD: 0.20 percent). Landon et al, as part of the MFMU cohort, measured but did not offer a 

definition of HIE.80 This study did not find the frequency of HIE to be significantly different in 

term women with one prior cesarean delivery compared with those with multiple prior cesarean 

deliveries (0.1 percent versus 0, p=1.0) or when comparing TOL versus ERCD in women with 

multiple prior cesarean deliveries (0 versus 0). Richardson et al used a very different approach 

from either of the other two and measured and reported on umbilical cord pH.284 This study 

found a slight decrease in the mean cord pH of women undergoing a TOL versus women who 

had an ERCD with no labor (7.24±0.07 versus 7.27±0.05, p< 0.001). There was a statistically 

significant difference in base excess in the TOL versus ERCD group (-5.3mmol/L ±3.1 versus ­

2.9mmol/L±2.5, p< 0.001). There were no significant differences in infants with umbilical artery 

pH of less than 7.00 in the same groups (TOL: 0.5 percent versus ERCD without labor: 0.1 

percent, p=NS). 

Summary and strength of the evidence on infant respiratory morbidity The strength of 

evidence on the HIE of the infant for VBAC versus ERCD was low due to lack of consistency in 

measurement and few studies. While the studies consistently report higher risk for HIE for TOL 

compared with ERCD, it is not possible to know the true relationship due to the low strength of 

overall evidence. 

131 
Sepsis 

Three fair quality cohort studies were found to address sepsis in the neonates of women who 

attempted a VBAC versus ERCD.79, 90, 97 Fisler et al found that neonates in a university setting 

who had a TOL had significantly more sepsis evaluations than did infants who underwent ERCD 

(23.3 versus 12.5 percent, p=0.0008) and significantly more antibiotic treatments (11.5 versus 

4.4 percent, p=0.02).90 The absence of predefined criteria for a sepsis evaluation and subsequent 

antibiotic therapy make interpretation of these results difficult. However, the impact of these 

interventions are not insignificant as the authors note that an evaluation for sepsis consisted of a 

complete blood count, blood culture, with lumbar puncture performed at the discretion of the 

practitioner. Sub analysis of the TOL neonates found increased sepsis evaluations and antibiotic 

therapy in the TOL group with an epidural compared with TOL neonates without an epidural 

(29.6 versus 6.0 percent, p=0.0001). Loebel et al also measured “suspected” sepsis, but found no 

significant differences in neonates born after a TOL versus those delivered by ERCD (3.5 versus 

2.7 percent, p= 0.38).97 

Hook et al similarly reported the incidence of sepsis in neonates who underwent TOL versus 

those delivered by ERCD. This study was unique in that it was conducted in three hospital 

settings (Level 1, 2, and 3) and measured the incidence of proven sepsis as well as suspected 

sepsis.79 While suspected sepsis was significantly increased for neonates born by VBAC 

compared with infants born after a TOL who then delivered by cesarean (12 versus 2 percent, p= 

0.001), there were no statistically significant differences between these groups when the outcome 

was “proven sepsis” (three infants [two percent] versus one infant [0.3 percent], p=NS). Infants 

without “proven sepsis” still received blood cultures and antibiotic therapy, but were not 

considered proven to be septic unless a positive blood culture was obtained. 

Summary and strength of the evidence on sepsis The overall strength of evidence for the 

impact of route of delivery upon infant sepsis is low due to imprecise and inconsistent definitions 

and few studies. While existing studies suggest that there is no significant difference between 

TOL and ERCD, serious limitations prevent a true understanding of the relationship between 

route of delivery and sepsis. 

Birth Trauma 

Two fair quality studies90, 93 provided information regarding neonatal trauma. In a large, 

population based study, Gregory et al found the frequency of trauma to be higher in women who 

attempted VBAC versus ERCD, regardless of whether the mother had a high-risk clinical 

condition (3.73 percent attempted VBAC versus 0.77 percent ERCD).93 Subanalyses found that 

among women who attempt VBAC those with a history of substance abuse were more likely to 

have neonatal trauma (odds ratio 4.4; 95 percent CI: 1.1 to 18.2) as were those with ruptured 

membranes longer than 24 hours (odds ratio 4.2; 95 percent CI: 1.7 to 10.2). This study used 

ICD-9 codes to define trauma (763.1,2,3,4; 7.67.2,3,4,5,6,7,8,9). These codes represented fetal 

malpositions and varying types of delivery affecting the fetus, as well as skeletal, nerve, and 

cranial injuries. 

In a prospective cohort study comparing neonatal outcome in low-risk women at term 

undergoing a TOL and low-risk women at term electing a RCD, Fisler et al measured mild 

bruising (defined as bruising confined to a single extremity) as well as birth injury (not 

defined).90 There was a significant increase in the number of infants who had mild bruising in the 

TOL group compared with the ERCD group (TOL: 8 percent versus ERCD: 1.5 percent, 

132 
p=0.0008); however no statistically significant differences were noted between TOL versus 

ERCD for birth injury (TOL: 1 percent versus ERCD: 1.5 percent, p=0.6). In this study, birth 

injury was not defined, but the authors noted three infants in the TOL group had 

cephaohematoma, while two infants in the ERCD group (no labor; scheduled repeat cesarean 

delivery group) experienced facial nerve palsy. 

Summary and strength of evidence on birth trauma The overall strength of evidence for the 

impact of route of delivery on birth trauma is low largely due to few studies. While existing 

studies suggest that there a nonsignificant increase in birth trauma for TOL, serious limitations 

prevent a true understanding of the risk of birth trauma for VBAC compared with ERCD. 

Apgar Scores 

While Apgar scores suffer from subjectivity and have little long-term predictive value, it is 

an established and accepted part of the neonatal assessment at the time of delivery. Four good or 

fair quality cohort studies79, 90, 103, 284 all reported no significant difference in 5 minute Apgar 

scores between infants in TOL groups versus infants in ERCD groups. 

Hook et al found no significant differences in an Apgar score of six or less at 5 minutes in 

infants who underwent a TOL (6/492, 1 percent) versus ERCD (3/497, 1 percent).79 Closer 

examination of the TOL group found significantly fewer neonates had an Apgar score of six or 

less at 5 minutes if they underwent a VBAC versus when the TOL resulted in a cesarean delivery 

(26/336, 8 percent versus 22/156, 14 percent, p<0.05). In a fair quality study, Richardson et al 

similarly found no significant differences in an Apgar score less than seven at 5 minutes in 

women who underwent a TOL after cesarean delivery versus those who underwent an ERCD 

(odds ratio 0.5; CI 95 percent 0.2 to 1.2. p= NS).284 However, in a smaller retrospective cohort, 

fair quality study, Fisler et al found no significant difference in neonates with an Apgar score of 

less than seven at 5 minutes between neonates who underwent a TOL (regardless of whether they 

had a VBAC) versus ERCD (1 percent versus 0, p=0.06).90 Smith et al, in a large, fair quality 

population study, found that while the overall incidence of very low Apgar (less than four) at 5 

minutes was rare, it occurred more frequently in infants who underwent a TOL (than among 

those who were delivered by an ERCD (105/15,515 [0.68 percent] versus 40/9014 [0.44 percent] 

p=0.02).103 

Summary and strength of evidence on birth trauma. Four studies found no differences in 

Apgar scores of less than six and seven at 5 minutes in infants undergoing a TOL versus ERCD. 

Three studies examined the differences in low Apgars (less than seven) at 5 minutes in VBAC 

versus RCD after a TOL; two of these studies found no difference in Apgar scores of infants 

born by VBAC versus RCD after a TOL. Future studies that include Apgar score results in their 

measures of morbidity could be improved by further followup of infants with low Apgar scores 

as an Apgar score is an intermediate measure of infant health, as well as close attention to 

classification of exposure to labor and delivery outcome. 

Neonatal Intensive Care Unit Admissions 

Admission to the NICU is a frequently measured short-term neonatal outcome and has been 

used as a proxy for serious morbidity. The significance of admission to the NICU can vary by 

hospital setting, provider experience, provider availability, and pre-established admission 

criteria. The amount of time a neonate spends in a NICU can vary from a short observation 

period to a lengthy stay, reflecting the severity of the neonate’s condition. 

133 
Eight studies that measured NICU admission met the criteria for review,78-80, 90, 97, 156, 284, 286 

but none explicated the criteria for NICU admission despite the existence of an American 

Academy of Pediatrics (AAP) policy statement on levels of neonatal care.289 While admission to 

a NICU can occur for multiple reasons, it is generally agreed that admission to the NICU results 

in separation of the neonate from its mother as well as contributing to an increase in the cost of 

healthcare. Three studies78, 80, 156 used reported on the same MFMU cohort. In a fair quality study 

on risk of uterine rupture in women undergoing TOL, Landon et al isolated term neonates to 

measure the frequency and likelihood of NICU admission in women who underwent TOL with 

one previous cesarean delivery compared with women with multiple cesarean deliveries.80 Of the 

17,898 women in the study, 95 percent had only one prior cesarean; the remainder of women 

undergoing TOL (N= 975) had two, three, and four prior cesareans. Nine percent of the term 

neonates whose mothers had one prior cesarean were admitted to the NICU compared with 11.2 

percent of the neonates whose mothers had greater than one prior (odds ratio 1.53; 95 percent CI: 

1.19 to 1.96, p=0.05); however this study did not find multiple prior cesareans to be predictive of 

uterine rupture (odds ratio 1.36; 95 percent CI: 0.69 to 2.69, p=0.37). Grobman et al, in a good 

quality study from the MFMU cohort, examined the effect of IOL on perinatal outcomes in 

neonates at term with one prior cesarean differentiating between one prior vaginal delivery and 

no previous vaginal delivery.156 There were no significant differences in admission to the NICU 

regardless of type of labor (spontaneous, induced , augmented) or whether women had a pervious 

vaginal delivery (odds ratio 1.19; 95 percent CI: 0 to 1.47) or no prior vaginal delivery (odds 

ratio 1.03; 95 percent CI: 0.85 to 1.24). In another study of good quality from the MFMU cohort, 

Hibbard et al set out to determine whether morbidly obese women have greater maternal and 

perinatal morbidity with TOL compared with ERCD.78 In this secondary analysis she found an 

increased incidence in the frequency of admission of term neonates to the NICU in women who 

were obese/morbidly obese (10 percent/13.8 percent) compared with women with a normal BMI 

(7.4 percent) or who were overweight (7.7 percent, p<0.001). However, neonates of morbidly 

obese women undergoing TOL were no more likely than neonates of women who had ERCD to 

experience admission to the NICU (13.8 versus 12.6 percent, odds ratio 1.1; 95 percent CI: 0.9 to 

1.3 percent). 

The remaining five studies79, 90, 97, 284, 286 addressing frequency and likelihood of NICU 

admission are summarized in Table 35. Two studies attempted to distinguish NICU admission 

after delivery by VBAC or RCD after TOL. In a study of good quality across all three hospital 

levels ,Hook et al found no significant increase in admissions to a Level 3 NICU in neonates 

born by TOL compared with ERCD (3 versus 2 percent, p=NS), but found significantly more 

neonates admitted to NICU if they were born by RCD following a TOL compared with those 

born by VBAC (7 versus 2 percent, p< 0.007).79 Similarly, Kamath et al, in a fair quality study, 

also found that RCD after TOL increased the likelihood of NICU admission (odds ratio 2.26; 95 

percent CI: 0.85 to 6.0, p=0.10).286 However, the greatest likelihood of admission to the NICU 

(adjusted for multiple covariates of maternal education level, chronic, disease, amniocentesis, 

choriamnionitis, non-reassuring fetal heart tones, and GA by week) was for term infants who did 

not experience labor and were born by ERCD (odds ratio 2.93; 95 percent CI: 1.28 to 6.72, 

p=0.011). 

While costs associated with care vary greatly by setting and region of the U.S., Kamath et al 

analyzed neonatal length of stay and found neonates born by VBAC stayed 3 days on average 

compared with 4 days for ERCD (with or without labor) and RCD after TOL (p<0.001).286 

134 
Summary and strength of evidence on neonatal intensive care unit admissions. Overall 

the strength of evidence on the impact of route of delivery on NICU admission is low due to 

inconsistent and imprecise measures. No studies defined the criteria for admission to the NICU. 

Six studies found no significant differences in frequency of NICU admissions between TOL and 

ERCD whereas one reported the greatest risk for NICU admission in infants undergoing an 

ERCD without labor (odds ratio 2.93) versus a successful VBAC (odds ratio 1.0). Future studies 

would benefit by description of NICU admission criteria, the reason for admission, and level of 

support provided to the infant. 

135 
Table 35. Neonatal intensive care unit admissions among term studies 

Study, year Design/Population N Comparison NICU measurement Outcome 

Fisler, 200390 Prospective cohort 

University hospital 

449 1. TOL versus ERCD 

2.TOL with epidural versus TOL without epidural 

Any NICU admission 1.TOL (26.2%) 

(17.6%), p= 0.02.TOL w/epiduTOL w/o epidu

Hook, 199779 Prospective cohort 

Level 1, 2, 3 hospital settings 

989 1. TOL versus ERCD 

2. VBAC versus TOLCD 

NICU admission 1. TOL (3%) ve

p=NS 2. VBAC (2%) vp< 0.007 

Grobman, 2007156 Prospective cohort MFMU 

19 academic medical centers 

11,778 1.No prior VD (SL v. 

IOL) 2.Prior VD (SL v. IOL) 

Special care nursery admission 

1.OR 1.03 2.OR 1.19 

Hibbard, 200678 Prospective observational cohort 

MFMU 19 academic medical centers 

28,446 TOL versus ERCD in 

obese women 

NICU admission by BMI 

Obese TOL (13(12.6%),OR 1.1 

Landon, 200680 

Observational cohort MFMU 19 academic medical centers 

17,890 1.TOL in women with 1 

prior CD 2.TOL in women with >2 prior CD 

NICU admission not specified 

1 prior CD (9%CD (11.2%), O

Loebel, 200497 Retrospective cohort Large community hospital 

affiliated with a university 

1,408 1.TOL versus ERCD 

2.VBAC versus ERCD 3. TOL-CD versus ERCD 

NICU admissions 1. TOL (4.2%) 

p= 0.24 2.VBAC (3.7%) p= 0.12 3. TOL-CD (6.2(5.6%) p= 0.78 

Richardson, 2005284 Prospective cohort Tertiary care hospital 3,489 TOL versus ERCD (no labor) 1.NICU triage 2.NICU admission 

3.NICU stay > 7 days 

1.TOL (0.8%) vAdjusted OR 22. TOL (8.8%) ERCD (8.3%) Adjusted OR 03. NICU >7 dayTOL (0.9%) veERCD (0.6%) Adjusted OR: 0
Table 35. Neonatal intensive care unit admissions among term studies 

Study, year Design/Population N Comparison NICU measurement Outcome 

Kamath, 2009286 Retrospective cohort university hospital 672 Planned TOL VBAC 

TOL-CD ERCD Labor No labor 

NICU Admission Planned TOL 

OR 1.0 OR 1.91 ERCD OR 2.26 OR 2.93 

Abbreviations: CD=cesarean delivery; ERCD=elective repeat cesarean delivery; MFMU=Maternal-Fetal Medicine Units Neintensive care unit; NS=not significant; OR=odds ratio; TOL=trial of labor; TOL-CD=trial of labor followed by a cesarean debirth after cesarean; VD=vaginal delivery 
Breastfeeding 

No studies were found that explored the effect of a TOL versus an ERCD on breastfeeding 

initiation or continuation. 

Impact of the Mode of Delivery on Subsequent Babies 

Two fair quality studies were found addressing the impact of a previous cesarean delivery on 

subsequent unexplained stillbirth in the next pregnancy.280, 281 Smith et al, using linked discharge 

data from a large, population database in Scotland, estimated the risk of antepartum stillbirth in a 

second pregnancy comparing women with a previous cesarean (N=17,754) to women with no 

previous cesarean.281 The study group included women with a second pregnancy from 1992 to 

1998 and excluded fetuses less than 500 grams, deaths due to congenital anomalies, and rhesus 

isoimmunization. There were 68 stillbirths in the previous cesarean delivery group. After 

attributed causes for the stillbirths (e.g., toxemia, hemorrhage, mechanical, maternal issues) were 

noted, there were more unexplained stillbirths found in the previous cesarean delivery group (43 

unexplained stillbirths out of 17,754 births or 0.24 percent of births) compared with women 

without a prior scar (163 unexplained stillbirths out of 102,879 births or 0.16 percent of births). 

Adjusting for maternal and demographic characteristics did not lessen the association between 

previous cesarean and unexplained stillbirth. Smith also used time-to-event analyses to predict 

the prospective risk of a stillbirth at 39 weeks or greater gestation to be 0.11 percent of women 

compared with 0.05 percent of women without a prior cesarean delivery. The authors noted that 

despite a wealth of clinical and demographic data in the dataset they did not have access to 

maternal weight, and therefore were unable to adjust for BMI and obesity as a maternal risk 

factor. 

In another large U.S. dataset, Bahtiyar et al conducted a cross-sectional study of singleton, 

term pregnancies from 1995 to 1997 in women with a prior cesarean delivery compared with 

women without a prior cesarean delivery, excluding any underlying maternal or fetal 

abnormality.280 Women were stratified in order to detect the study group of interest and to reduce 

potential confounders, with the final group of women with only one prior delivery (cesarean 

versus vaginal birth). Rate of stillbirth in the subsequent pregnancy was compared between the 

two groups. While not statistically significant, there were fewer stillbirths in the previous 

cesarean group compared with women without a prior cesarean in the second pregnancy (0.072 

percent of births compared with 0.080 percent of births, RR 0.90; 95 percent CI: 0.076 to 0.106 

percent). While this study is strengthened by its large cohort size (1.7 million for comparison in 

the study group described), it was difficult to determine the exact number of cases in each 

current pregnancy group. The authors did not attempt to classify stillbirths by cause and based 

study data on birth and death certificates. 

Summary of mode of delivery on subsequent babies. Two studies were reviewed to 

determine the risk of stillbirth in subsequent pregnancies in women with a prior cesarean 

delivery. These studies produced conflicting results with one study showing that prior cesarean 

increases the risk for unexplained stillbirth in next pregnancy and the other study showing no 

difference in risk for stillbirth in the next pregnancy. One study included early gestations, while 

the other study was limited to term gestations. Both studies are limited by their retrospective 

design and relied on large perinatal databases while employing various methodologies to 

overcome confounding. 

138 
 

Neurological Development 

No studies were found that measured the impact of a TOL versus an ERCD on neonatal 

neurological development. In order to examine the neurological development, studies that extend 

beyond the immediate postpartum period would be required. 

Special Considerations 

Impact of induction upon infant outcomes. 

Prostaglandin E2. Several studies reported the rate of infants with Apgar scores of less than 

seven at 5 minutes among those with PGE2 induction, ranging from 0 to 8 percent, but rates were 

similar to the control group in each individual study.145, 148, 149, 153, 161, 168 Other infant harms were 

not reported consistently. 

Misoprostol. Evidence for infant harms associated with misoprostol used for cervical 

ripening and labor induction is not adequate to make conclusions. As described in previous 

sections, a small cohort study (N=226) of term gestations, comparing PGE2 (administered as a 

gel or pessary) with misoprostol (25 to 50 mcg) included only 16 of 145 women in the 

misoprostol group and nine of 81 in the PGE2 group who had a history of a prior cesarean 

delivery.211 Only the results for uterine rupture were stratified by history of a prior cesarean with 

two of 16 in the misoprostol group (13 percent) and zero of nine in the PGE2 group having a low 

transverse rupture. In one case, the Apgar scores were two and seven at 1 and 5 minutes 

respectively, and the neonate’s outcome was good. The other resulted in a stillbirth. The only 

other study made comparisons among women with a history of prior cesarean delivery to those 

without prior cesarean delivery (with no limit on GA), a comparison that is not relevant to this 

review.172 Among the group with a prior cesarean delivery and a TOL with misoprostol for 

cervical ripening (N=48) fetal distress was reported in 23 percent, and 13 percent of infants had 

an Apgar score of less than seven at 5 minutes. 

Mifepristone. In a small (N=32), fair quality trial of mifepristone compared with placebo— 

each given for 2 days followed 2 days later by induction with prostaglandins, oxytocin, and/or 

artificial rupture of membranes as needed in women with term gestations—neonatal outcomes 

were similar between groups, but one baby in the mifepristone group had hypoglycemia at 

birth.173 

Oxytocin versus prostaglandin. None of the studies comparing oxytocin and PGE2 for 

induction stratified neonatal outcomes based on which drug was used. 

Mechanical methods of induction. Reporting of infant harms was inadequate in the limited 

number of studies of mechanical induction to allow comparative assessment. 

Macrosomia. Fetal macrosomia is a common obstetric condition known to present in 

approximately 10 percent of all infants in the U.S. and has the potential to influence the route of 

delivery on infant outcomes. Though there is inconsistency in definitions, macrosomia most 

commonly is used to refer to fetal weights greater than 4,000 or 4,500 grams. Clinicians are 

frequently called upon to weigh the risks and benefits of a TOL after a prior cesarean delivery in 

women with suspected fetal macrosomia. Neither ultrasound nor physical examination is able to 

accurately estimate fetal weight. 

Eleven good or fair quality studies reported on the impact of fetal macrosmia on infant 

outcomes for VBAC compared with ERCD.60, 78, 117, 123, 124, 126, 139, 161, 188, 221, 267 Studies that 

examined the relationship of fetal macrosomia and uterine rupture as well as the incidence of 

macrosomia in the presence of maternal obesity are also discussed. 

139 
 

The incidence of macrosomia increases as gestational age increases. Rates of macrosomia 

increased from 2 percent in a cohort of preterm women to 9.1 percent of women at term to 25.5 

percent of women at 41 weeks or greater.60 

Nine studies were reviewed that addressed the VBAC rate within cohorts when the birth 

weight exceeded 4,000 grams.60, 117, 123, 124, 139, 146, 161, 221, 267 Five of these studies used regression 

analyses to compute the likelihood of VBAC or RCD after TOL based upon birth weight greater 

than or less than 4,000 grams.123, 124, 139, 146, 267 In a retrospective cohort study of good quality, 

Bujold et al evaluated VBAC in women according to their BMI (N=8580) and found women 

who delivered infants weighing 4,000 grams or greater were less likely to have a VBAC (odds 

ratio 0.62; 95 percent CI: 0.54 to 0.71, p<0.001).267 This study excluded patients with known 

pregestational diabetes, but did not control for gestational diabetes or for the indication for prior 

cesarean delivery, which is acknowledged to influence VBAC rate. 

The majority of studies reported the relationship of VBAC in infants weighing greater than 

4,000 grams with those weighing less than 4,000 grams.60, 126, 139, 161, 188, 221, 267 Two fair quality 

studies117, 124 furthered their analyses by examining VBAC rates in mothers whose infants 

weighed greater than 4,000 grams and less than 4,500 grams. Without controlling for parity, 

number of prior cesarean deliveries, or vaginal births, El-Sayed et al found a higher VBAC rate 

in women delivering infants greater than 4,000 grams (11.6 percent) compared with women 

delivering infants greater than 4,500 grams (1.3 percent, p<0.001).124 Birth weight greater than 

4,000 grams was associated with a RCD after a TOL (odds ratio 2.65; 95 percent CI: 1.70 to 

4.13). Likewise, in a prospective descriptive study of women in 25 free-standing birth centers in 

the U.S., Lieberman et al found a VBAC rate of 17.4 percent in women whose infants weighed 

4,000 to 4,499 grams compared with 5.8 percent in women whose infants weighed 4,500 grams 

or greater.117 

Elkousy et al, in a fair quality study, differentiated VBAC rates in women delivering 

macrosomic infants into two categories (4,000 to 4,249 grams and 4,250 to 4,500 grams) as well 

as comparing VBAC rates in women with infants weighing less than 4,000 grams versus those 

whose infants weighed greater than 4,000 grams and greater than 4,500 grams.123 The adjusted 

incidence ratios for VBAC were reduced only slightly in each infant weight category: 4,000 to 

4,249 grams (0.85; 95 percent CI: 0.77 to 0.93); 4,249 to 4,500 grams (0.77; 95 percent CI: 0.66 

to 0.89); greater than 4,500 grams (0.70; 95 percent CI: 0.57 to 0.077). 

Three studies examining the relationship of neonatal macrosomia in women with increased 

BMI and VBAC were reviewed.78, 126, 267 The impact of increasing maternal weight gain on 

VBAC rate was previously discussed in the section on Special Considerations of maternal 

outcomes. In a good quality retrospective cohort of women (N=6718) undergoing a TOL, Bujold 

et al noted increases in the mean birth weight of infants and rates of macrosomia as maternal 

BMI increased.267 Likewise, in a secondary analysis of a prospective good quality study, Hibbard 

et al noted a significant increase in the birth weights of women of normal BMI (3,196±445 

grams), compared with women who were overweight, obese, or morbidly obese (3,370.5±451.3, 

3,4692±471.5, 3,493.8±503.4, p<0.001).78 While no separate analysis was performed on infants 

specifically weighing 4,000 grams or greater in this study, it is clear from these two studies there 

is positive correlation of increased birth weight with increasing maternal BMI. A fair quality 

study by Goodall et al also found that compared with women with a normal BMI, morbidly 

obese women were more likely to have infants greater than 4,000 grams (p=0.004).126 

There were no studies that examined neonatal trauma in infants whose birth weights 

exceeded 4,000 grams. 

140 
 

 

Summary of macrosomia. There is a trend toward an increase in mean birth weight as 

maternal BMI increases. There is evidence for a decreased likelihood of VBAC in infants 

weighing 4,000 grams or greater (odds ratio 2.65); this trend is more pronounced in infants 

weighing 4,500 grams or greater compared with less than 4,500 grams (1.3 percent if greater 

than 4,500 grams versus 11.6 percent if less than 4,500 grams, p<0.001). 

Fetal presentation. No studies were found that measured the impact of fetal presentation on 

the benefits or harms of a TOL versus an ERCD. 

Gestational age. Because of the potential confounding for neonatal harms introduced by 

preterm gestation, a review of neonatal benefits and harms after a TOL versus an ERCD were 

limited to term infant outcomes. One fair quality study of term infants by Kamath et al reported 

selected neonatal outcomes at 37, 38, 39, 40, and greater than or equal to 41 completed weeks of 

gestation.286 Because neonatal outcomes were compared by GA rather than denoting the intended 

mode of delivery in this study, it is impossible to draw any conclusions regarding the influence 

of GA on neonatal outcomes in women who attempt a TOL versus ERCD.286 

Recent recommendations by ACOG state that infants not be delivered by ERCD or elective 

IOL before 39 weeks due to the increased risk of iatrogenic prematurity and the potential for 

respiratory complications. Likewise, post term pregnancies carry an increased risk of 

complications (e.g., meconium passage and non-reassuring fetal heart rate patterns), potentially 

influencing the route of delivery. While the study by Kamath et al stratified neonatal outcomes 

by GA and found that infants delivered at 37 weeks had the highest rates of oxygen use in the 

delivery area (38.8 percent, p=0.003) and the most admissions to the NICU (15 percent, 

p=0.018), they do not go on to stratify those outcomes by the intended or actual mode of 

delivery. Future studies that examine the influence of GA on VBAC rate compared with RCD 

after TOL and ERCD are warranted.286 

Summary of gestational age. Analysis was limited to term neonates due to the potential for 

confounding for neonatal harms introduced by preterm gestational age. Only one study reported 

selected neonatal outcomes by gestational age in the term infant, but did not classify the infant 

by mode of delivery. There is insufficient data to determine that gestational age in term neonates 

influences benefits or harms to the neonate undergoing TOL versus ERCD. 

141 
1

 1

 

Chapter 4. Discussion 

Each year 1.5 million childbearing women have cesarean deliveries, and this population 

continues to increase. While cesarean deliveries represent a third of all births, they account for 

almost half of the childbirth-related expenses of hospitalization at $7.8 billion annually.1 

Therefore, the appropriate and safe use of cesarean and vaginal birth after cesarean (VBAC) is 

not only an individual patient- and provider-level concern but it is also a national health policy 

concern. 

Prior cesarean delivery is the most common indication for cesarean, accounting for over a 

third (534,180,000) of cesarean deliveries, almost twice the rate of any other indication. Thus, an 

important contributor to the increase in cesareans is the rapid decline in VBACs witnessed over 

the last decade. In 2007, only 8.7 percent of childbirth-related hospitalizations among women 

with a previous cesarean delivery were VBACs, suggesting that over 90 percent of all women 

with a previous cesarean will deliver by planned or elective repeat cesarean delivery (ERCD). 

One of the major findings of this report is that the best evidence suggests that VBAC is a 

reasonable and safe choice for the majority of women with prior cesarean. Moreover, the report 

raises concerns over the serious morbidity accruing from multiple cesareans, a result of the 

increased use of ERCD over VBAC. In addition to health outcomes, some relatively unexamined 

contextual factors relating to VBAC drive patient, provider, hospital, and policy decisionmaking. 

Regional-, hospital-, and individual-level liability have all been associated with increased 

cesarean delivery rates. Even a perception of increased risk for liability was reported to be 

associated with increased use of cesarean. Similarly, some data suggest that economic incentives 

appear to affect cesarean delivery rates. It is financially untenable for many rural hospitals to 

offer the 24-hour in-house availability that is suggested to allow VBAC as an option. Economic 

incentives may need to be changed to prioritize access to VBAC services. Patients and providers 

are influenced by the short- and long-term benefits and risks of route of delivery as well as 

family obligations, costs, societal norms, and regional availability of options. Although studies of 

VBAC are numerous, the numbers of studies providing high quality information on important 

clinical questions are limited. 

The literature concerning trial of labor (TOL) and ERCD is flawed in several ways: 

imprecise measurement of outcomes (e.g., maternal infection, perinatal death), making it difficult 

to determine the portion of events directly attributable to route of delivery; lack of standards for 

terminology (e.g., no standard classification for severity of health consequences related to uterine 

rupture); and limited attention to comparability between groups (e.g., studies of ERCD in which 

it is unclear whether patients were eligible for TOL). Data on maternal and infant outcomes, of 

great interest to most patients, suffer from a lack of standardization of terminology and 

measurement. This is especially highlighted by the trends seen with studies reporting both 

hemorrhage and transfusion in TOL and ERCD. In studies where hemorrhage was reported as 

higher in one group, the transfusion rates were lower. Additionally, alternative interventions to 

transfusion, such as IV iron therapy, were not reported. Investigations into the neonatal effects of 

ERCD and VBAC suffer even greater problems of measurement, lack of standardization, and 

insufficient data. How, then, are these studies to be interpreted by the individual clinician, much 

less combined for guidance? Further complicating interpretation are both the unreported societal 

and monetary costs of intervention associated with these modes of delivery. This highlights a 

Appendixes and evidence tables cited in this report are available at http://www.ahrq.gov/downloads/pub/evidence/pdf/vbacup/vbacup.pdf. 

143
 
particular problem with the research in this area; the easiest outcomes to measure are not 

generally the outcomes most pertinent to the clinician or the patient. 

Studies of VBAC versus ERCD have traditionally reported outcomes based upon actual route 

of delivery rather than intended route, leading to misclassification of patients who intend ERCD 

but go into labor prior to their cesarean or women who intend TOL but who are delivered by 

cesarean. A good demonstration of the complexity of this issue comes from the first National 

Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network 

(MFMU) studies. The studies report on 45,988 women with singleton gestation and prior 

cesarean delivery at term. The original article by Landon published in 2004221 considered women 

who presented in labor at 4 cm or greater cervical dilation or anyone receiving oxytocin in the 

TOL group; and women who presented in early labor who subsequently underwent cesarean 

were excluded. Ultimately, 12,289 women (27 percent of population at term with prior cesarean 

delivery)--9,013 who had an indicated repeat cesarean delivery (IRCD) and 3,276 women who 

presented in early labor and subsequently delivered by cesarean delivery--were excluded from 

the analysis. Thus Landon’s analysis presented data for 33,699 women: 17,898 women classified 

as undergoing TOL and 15,801 undergoing an ERCD. Uterine rupture rates in these two groups 

were 124/17,898 (0.7 percent) in TOL versus 0/15,801 (0 percent) in ERCD. A subsequent 

analysis performed by Spong in 2007204 aimed to provide information that would be clinically 

useful to the clinician providing antepartum counseling for VBAC and classified patients quite 

differently. She broke the group into three main categories: TOL (15,323), ERCD (17,714, 

without medical indication), and IRCD (6,080). Ultimately, not only did she include 5,418 

additional patients for a total of 39,117, but 2,575 women who were initially considered TOL in 

Landon’s study were now distributed to either IRCD or ERCD with labor. While this 

reclassification did not change the uterine rupture rate for the TOL group (0.74 percent in 

Spong204 versus 0.7 percent for Landon221), it substantially changed the uterine rupture rate 

among the ERCD group (without indication). 

The design of most studies, including the largest and widely cited Spong study discussed 

above, render them unable to identify the ideal population - women who plan VBAC or plan 

RCD. The evidence from these studies is at best indirect and difficult to apply to a woman who 

plans for either option. These studies also lack data concerning important contextual factors such 

as whether and how hospital structure, setting, staffing, economics, and liability affect processes 

and outcomes. Each potential bias leaves clinicians and patients uncertain of the ramification for 

their decisionmaking and masks potential adverse effects of desiring one route of delivery but 

having another. 

A longitudinal study design that begins after first cesarean and measures patient intent would 

allow measurement of outcomes, preferences, and adverse events throughout the entire spectrum 

of concepts presented in the analytic framework. Because issues of access and capacity to handle 

obstetric emergencies, such as uterine rupture, are likely to impact a woman’s ability to have the 

delivery she desires as well as the ultimate outcome of any emergency, a national study that 

could examine regional variation would be ideal. 

Table 36 summarizes the strength of evidence and findings for all key questions reviewed in 

this report. Briefly, there is moderate evidence that women who have a TOL have a high 

probability of having a vaginal delivery (74 percent) which can be enhanced by maximizing 

favorable clinical conditions such as waiting for a favorable cervical examination if possible. 

Overall, maternal morbidity is reduced from TOL compared with ERCD. Of particular note is 

the significantly decreased risk of maternal mortality and the serious morbidity associated with 

144
 
multiple repeat cesareans. Overall--with the exception of perinatal, fetal, and neonatal mortality 

rates, which are significantly higher for TOL--the literature on neonatal outcomes are 

insufficient. Therefore, the inherent complexities of weighing maternal and infant risks remain a 

challenge for clinicians and patients. 

A systematic review strives to be patient-centered and to provide both patients and clinicians 

with meaningful numbers or estimates so they can make informed decisions. Often, however, the 

data do not allow a direct estimate to calculate the numbers that people desire such as the number 

of cesareans needed to avoid one uterine rupture related death. The assumptions that are required 

to make such estimates from the available data introduce additional uncertainty that cannot be 

quantified. If we make a simplistic assumption that 6 percent of all uterine ruptures result in 

perinatal death (as found from the summary estimate), the range of estimated numbers of 

cesareans needed to be performed to prevent one uterine rupture related perinatal death would be 

2,400 from the largest study,204 and 3,900-6,100 from the other three studies of uterine rupture 

for TOL and ERCD.10, 97, 205 Taken in aggregate, the evidence suggests that the approximate risks 

and benefits that would be expected for a hypothetical group of 100,000 women at term 

gestational age (GA) who plan VBAC rather than ERCD include: 10 fewer maternal deaths, 650 

additional uterine ruptures, and 50 additional neonatal deaths. Additionally, it is important to 

consider the morbidity in future pregnancies that would be averted from multiple cesareans 

particularly in association with placental abnormalities. 

One persistent trend emerging from analysis of the evidence in this report is the influence of 

GA on vaginal delivery rates and outcomes. There appears to be increased risk of uterine rupture 

and transfusion among term pregnancies undergoing TOL. Further, limited information from 

induction studies suggests that risks of induction are particularly increased as GA exceeds 40 

weeks. These data together pose a particular challenge for the management of the post-date 

pregnancy. Mode of delivery for subsequent pregnancies poses a difficult question for women 

with prior cesarean and their providers. Some women have already made their decision prior to 

leaving the hospital after their cesarean due to factors surrounding that birth. Others will decide 

early in pregnancy, and still others will remain undecided until presenting in labor. Some women 

will not have a choice due to provider, hospital, insurance, or medical-legal factors that mandate 

RCD. This report suggests that, although there are statistically significant differences between 

ERCD and TOL, there are few clinically significant differences. 

145
 
Table 36. Summary of evidence for key questions 

Key Question Study Type* 

GRADE of Evidence Findings 

Among women who attempt a trial of labor after prior cesarean, what is the vaginal delivery rate and the factors th

Individual Risk Factors Cohorts N/A • In U.S. studies launched after 1996, les

had a TOL. 

• Most evidence of TOL and VBAC rates 

in large tertiary care centers or teaching 

• While TOL rates reported in observation

over time, VBAC rates have remained cwho have a TOL. 

• In studies based in the U.S., 74% of wo

delivered vaginally. 

Predictive Tools Cohorts N/A • All scored models provide reasonable a

who are good candidates for 

• VBAC but none have discriminating abi

identify women who are at risk for CD. 

What are the short- and long-term benefits and harms to the mother of attempting trial of labor after prior cesarean cesarean delivery, and what factors influence benefits and harms? 

Maternal Death Cohorts High • Overall, maternal death is a rare event 

approximately 10/100,000 when all stud

• Mortality appears to be increased with E

TOL, however the difference is not stati

• For both TOL and ERCD, a trend was s

maternal mortality in studies including acompared with term delivery limited stu
Table 36. Summary of evidence for key questions 

Key Question Study Type* 

GRADE of Evidence Findings 

Uterine Rupture Cohorts Moderate 

(Low uterine segment thickness studies only) 

• The rate of uterine rupture for all wome

very low 0.30% (3/1,000) 

• the risk of uterine rupture for women un

ten times higher than for women underg

• Overall, the risk of perinatal death in the 

rupture was 6.2% 

• There were no uterine rupture associate

among term studies 

• The overall risk of rupture with any indu

was 1.5% and 1.0% when any gestation

• Among women with gestational age > 4

highest at 3.2%. 

• There was significant heterogeneity am

• Study design appeared to play a role in 

uterine rupture 

Predictors of uterine rupture Cohorts, case 

series and case-controls 

N/A • Uterine rupture risk is decreased by prio

prior VBAC 

• Uterine rupture risk is increased by sho

<18-24 months and gestational age 

• There is insufficient or conflicting eviden

single layer closure, preterm delivery, mstatus, birth weight, oxytocin, prostagla

• ultrasound measurements of uterine thi

promising role in predicting populations 

Predictive Tool Cohorts N/A • Accurate and reliable tool to predict an ind

uterine rupture has not been achieved. 

Hysterectomy Cohorts Medium • Hysterectomy is rare with either ERCD or T

than 3% of deliveries 

• Hysterectomy rate for ERCD ranged from 0

• Hysterectomy rates for TOL ranged from 0.• The majority of studies report a non-signific

hysterectomy for ERCD 

• High-risk populations (maternal complicatio

risk for hysterectomy 
Table 36. Summary of evidence for key questions 

Key Question Study Type* 

GRADE of Evidence Findings 

Hemorrhage/Transfusion Cohorts Medium/Low • Overall hemorrhage rates were higher in th

versus 0.6-17% for any gestational age 

• Transfusion rates in TOL were 0.8% versus 

gestational age, compared with 0.66% TOL term delivery only studies 

• Transfusion risk appears to be modified by 

delivery 

• Data on maternal hemorrhage is limited by 

and definition of the term hemorrhage amo

Infection Cohorts Low 

(All definitions of infection) 

• TOL appears to be associated with increas

morbidity for populations that include pretestudies limited to term. 

• TOL is associated with a decreased risk of 

compared with ERCD (RR= 0.63, 95%CI= significant discrepancies exist in the definit

Surgical Injury Cohorts N/A • There is insufficient data regarding risk of s

and ERCD patients 

• Prior vertical cesarean is associated with in

injury 

Embolic events Cohorts N/A • TOL is associated with lower rates of embo

with ERCD (0.04% versus 0.1%) 

• The risk of embolic events for ERCD is sim

number of prior cesareans at 0.1% 

• Data is limited for this outcome 

Length of stay Cohorts N/A • TOL had a mean difference in LOS for all s

ERCD 

• Mean LOS difference for TOL was -1.3 day

• Obesity was associated with increased hos

limited 

Effect of Hospital Setting Cohorts N/A • Data are based on only one study which re

of short term complications in low volume m(particularly death and uterine rupture) 

• No studies directly describe the long-term 

VBAC, and ERCD 
Table 36. Summary of evidence for key questions 

Key Question Study Type* 

GRADE of Evidence Findings 

Multiple cesareans and placenta Cohorts N/A • >3 prior CD is associated with increased ra

accreta (4.7-6.7%), and hysterectomy (1.1

• Prior CD is a significant risk factor for mate

with previa. The risk increases with increas

• Women with ≥3 prior CD and previa had a 

increased risk of accreta (3.3-4% vs. 50-67

4% vs. 50-67%), and composite maternal compared with women with previa and no 

What are the short- and long-term benefits and harms to the baby of maternal attempt at trial of labor after prior cerepeat cesarean delivery, and what factors influence benefits and harms? 

Apgar scores Cohorts N/A • There is little to no significant difference be

infants delivered by VBAC and ERCD 

Respiratory complications Cohorts TTN: Low 

Bag/Mask: Low Intubation: Moderate 

• Few studies define terms for respiratory co

little consensus between studies regarding (VBAC versus ERCD) in regards to this in

Sepsis Cohorts Low • Definition of infantile sepsis is unclear, few 

of this diagnosis and even fewer measure sepsis. 

Asphyxia/HIE Cohorts Low • There are no consistent definitions of HIE 

few report it. Needed: neonates diagnosed followed to measure associated long-term 

NICU admissions Cohorts Low • No consistent definition for NICU admissio

between VBAC/ERCD. Currently: NICU admeasure of infant health, as reason for adgreatly between cases. Study findings are classification bias 

Stillbirth/Infant death Cohorts Perinatal: Moderate 

Fetal: Low Neonatal: Moderate 

• Conflicting evidence of whether a previous 

for stillbirth in subsequent pregnancies. 

• Perinatal and infant deaths are rare, but o

often in ERCD 

Neurological Development Cohorts Insufficient • No studies measure neurologic developme

beyond the immediate postpartum period neurological development 

Macrosomia Cohorts N/A • Heavier women have heavier babies, mac

likely to be delivered by VBAC, especially 
Table 36. Summary of evidence for key questions 

Key Question Study Type* 

GRADE of Evidence Findings 

Fetal presentation Cohorts N/A • No data on fetal presentation 

Gestational age Cohorts N/A • Analysis for Key Question 3 was limited to 

broke down term data by week in a VBAC 

Breastfeeding Cohorts Insufficient • No studies to determine breastfeeding ind

What are the critical gaps in the evidence for decision-making, and what are the priority investigations needed to 

 None N/A • Because studies largely report actual route 

subject to misclassification bias which weamagnitude and direction of risk for TOL ve

• Ideal cohort study would construct cohort 

delivery 

• Infant outcomes are poorly defined and ad• Important associations and outcomes for u

addressed 

• Rate and predictors for uterine- rupture as

maternal mortality and morbidity 

• Reliability for signs and symptoms of ruptu

• How hospital staffing, structure, etc impac

rupture 

Abbreviations: CD=cesarean delivery; CI=confidence interval; ERCD=elective repeat cesarean delivery; g=grams; HIE=hypencephalopathy; LOS=length of stay; N/A=not applicable; NICU=neonatal intensive care unit; RR=relative risk; TOL=trial o

tachypnea of the newborn; U.S.=United States; VBAC=vaginal birth after cesarean section; VD=vaginal delivery 
 

What are the critical gaps in the evidence for 

decisionmaking, and what are the priority investigations 

needed to address these gaps? 

Future research sections of evidence reports have been criticized for not providing sufficient 

detail to provide researchers the information they need to improve their study designs.290 Further, 

evidence reports have been dismissed for cataloging all possible research efforts rather than 

prioritizing future research. To take advantage of the peer review process—which distributes the 

draft report to federal agencies, including the FDA, CDC, and NIH; maternity and pediatric 

clinicians; advocacy groups; payers; policymakers; content experts; and researchers—our peer 

reviewers were asked to provide feedback on both investigator ideas on important gaps in the 

literature and to provide their own perspectives and priorities for future research. Specifically, 

experts were asked if stated topic areas were of low, medium, or high priority for future research, 

and to also provide additional clarification on their positions. Those areas that were rated as 

highest priority are discussed here (highest priority means that 50 percent of the experts rated the 

domain as high). 

The decision on route of delivery for women with prior cesarean delivery is particularly 

challenging and complex for patients, providers, and decisionmakers. Patients and providers are 

influenced by the short- and long-term benefits and risks of route of delivery as well as family 

obligations, costs, societal norms, and regional availability of options. Although the numbers of 

studies on VBAC are numerous, the numbers of studies providing high quality information on 

important clinical questions are limited. An analysis of the areas with the most uncertainty, gaps 

in the evidence, is presented in Table 37. While many believe the ideal study design for an 

intervention such as TOL versus ERCD would be a randomized controlled trial, none has been 

done, and several papers indicate that such a trial is unlikely in the U.S.291 The evidence for this 

systematic review is based almost entirely on observational studies, which are more susceptible 

to bias. Misclassification of patients and outcomes is a challenge to this literature. Steps to 

improve these areas in research are necessary to provide clinicians and families with accurate 

and timely information on route of delivery. In particular, studies of VBAC versus ERCD have 

traditionally reported outcomes based upon actual route of delivery rather than intended route. 

This can lead to misclassification of patients who intend ERCD but go into labor prior to their 

cesarean or women who intended TOL but who are delivered by cesarean delivery. Each leads to 

misclassification of outcomes for a particular group, and leaves clinicians and patients still 

uncertain of the ramification for their decisionmaking. It also masks the potential adverse effects 

of desiring one route of delivery but having another either due to medical complications or other 

reasons. 

National Childbirth Study 

Investigators and reviewers agree that the existing evidence is insufficient to adequately 

answer several questions (Table 37). Additionally, it was agreed that the most effective way to 

address these gaps in the literature is the undertaking of a large, prospective longitudinal national 

childbirth randomized trial or cohort study. Participants would need to be enrolled early in their 

pregnancy, and grouped by their intended route of delivery. Whether randomized or a cohort, 

this landmark study would use clearly defined outcomes, preferences, and risk factors. Such a 

study would be designed to follow women and their fetuses/infants from early pregnancy to 

151 
long-term followup. This type of study would allow researchers and clinicians to establish a 

cohort at risk. Investigators and experts also agreed on the importance of establishing the 

appropriate definitions for maternal outcomes (such as, infection, hemorrhage, and surgical 

injury) and for infant outcomes (such as death or respiratory or neurological issues). A 

prospective approach is paramount, given the problems with variation in patient classification, 

outcome definition, and method of measurement found in retrospective studies. Outcome 

definition was noted as being critical to interpretation of the literature by peer reviewers, and as a 

main problem in synthesizing existing evidence by reviewers. Composite outcomes are 

particularly problematic, although even individual outcomes were often poorly defined or 

defined with wide variation in the existing literature. A consensus conference on health outcome 

definitions with key leaders in the field should be held prior to conducting such a study. It is 

recognized that enormous challenges may exist in developing such a large scale effort. These 

include but are not limited to establishing consensus on definitions; acquiring funding; 

delineating external influences (litigation; popular press; and societal, patient, and provider 

assumptions); and obstacles to randomization, IRB approval, and long-term followup. 

In addition to, or in support of, such a study, there are specific questions for which an RCT is 

possible and the best methodological approach. Administrative or other types of databases may 

be useful in assessing some outcomes, particularly long-term harms. However, methods for using 

such databases in studying VBAC need to be developed. 

Specific areas identified that require additional research included prediction tools, maternal 

health outcomes, infant health outcomes, and cost. 

Prediction Tools 

Of priority to the experts surveyed in this domain include the ability to predict uterine 

rupture, VBAC, or emergency cesarean delivery (failed TOL). This report identifies gaps in the 

ability of existing prediction tools at selecting women for a successful TOL. Studies need to be 

large and prospective in nature and should use standard health outcome definitions. Such tools 

should address non-medical factors associated with a successful or failed TOL; the impact of 

induction; and whether there are differences among racial, ethnic, or socioeconomic groups. 

Where differences exist, future research should be designed to identify the reasons for such 

differences. 

Maternal Health Outcomes 

Better understanding of the short- and long-term outcomes comparing VBAC with ERCD is 

needed, particularly in order to inform women’s choices, especially among those who will have 

future pregnancies. This is especially important looking at the proportion of women who have 

three or more children and the extent of unplanned pregnancies. Future studies must include a 

full range of reproductive outcomes, including quality of life. Current evidence is lacking in 

standardization of definitions of short-term outcomes as well as methods of ascertainment and 

reporting. Examples of short-term outcomes that require better research are infection and 

surgical injury. Outcomes that affect both mother and infant, such as those related to 

breastfeeding and parental attachment, have not been studied in relation to VBAC. Comparison 

of long-term outcomes between VBAC and ERCD are also in need of better examination, with 

better evaluation of the impact of the age of the mother being taken into account along with 

multiple other factors. 

152 
Uterine rupture. Interpretation of the uterine rupture research is difficult for the many 

reasons previously described. A potentially promising area of inquiry might be using imaging to 

predict UR or outcomes; however, the current evidence in this area is insufficient for using 

ultrasound imaging of the uterine scar or lower uterine segment to predict the risk of uterine 

rupture with TOL. A large multi-centered RCT could take one of two approaches: randomize 

patients to ultrasound or no ultrasound, or perform ultrasound on all patients but randomize 

which providers receive the results prior to delivery. 

The impact of setting on the short- and long-term outcomes for mothers and infants has not 

been well studied. A prospective study of uterine rupture could be created to answer several 

questions. The study would need to use a standard definition and method of ascertainment to 

compare events at various types of hospital and non-hospital settings, with variation in staffing 

and the ability to provide “immediate access to cesarean delivery.” Implementation of a national 

registry of ruptures and using linked data systems may be a way to approach these questions. 

Evidence on the risk of uterine rupture when induction or augmentation is needed is lacking 

appropriate comparison groups and long- or short-term evidence on infant and maternal harms. 

Women who are candidates for induction should be compared with similar women who undergo 

expectant management. Additionally, the role of uterine wall thickness has not been studied in 

relation to induction for TOL. The best study to answer these questions is an RCT of induction or 

expectant management. The effect of uterine wall thickness could be examined within such a 

study or as a separate study. 

Infant Health Outcomes 

Experts and reviewers agreed that two pressing issues in VBAC continue to be identifying 

and then studying the most meaningful infant outcomes and agreeing on clear and precise 

definitions and methods of ascertainment. Although similar issues are seen with maternal 

outcomes and definitions, those reported as specific to infants include evaluation of variation in 

gestational age associated with the different delivery methods (ERCD and TOL with and without 

induction). 

Cost 

Costs were not examined explicitly in this report, but experts expressed the need to correlate 

beneficial or harmful outcomes to health-system costs. Economic analyses could be designed to 

coincide with studies described here. Additional studies to identify the best reimbursement 

model to provide financial incentives for critical elements of VBAC—which may include 

increased access in rural areas, 24 hour in-house surgical coverage, etc.—are needed. Again, 

clear definitions of outcomes are essential. 

153 
Table 37. Future research 

Research Question 

Create standard for 

referencing predictors 

Predicting TOL 

What are the predictors of 

a cesarean after a TOL? 

How often do uterine 

ruptures that occur in 

hospitals result in serious 

harms for mother or 

infant? How does this 

vary by setting? How 

does this compare to nonhospital births? 

What are the long-term 

maternal outcomes of 

VBAC versus ERCD? 

What are the rates and 

differences of infections 

of VBAC versus ERCD? 

What is the rate of 

specific surgical injuries 

with ERCD and TOL? 

What are appropriate 

definitions for maternal 

outcomes (such as, 

infection, hemorrhage, 

surgical injury, etc)? 

Domains Pertaining to Overall Strength of Evidence 

Results of Literature 

Review Types of Studies Needed to Answer Question 

Each study uses 

different reference in 

their analysis of 

predictor making 

pooling difficult. 

Evidence review to propose stand way to compare 

predictors. E.g., prior CD indication (breech) could 

always be compared to “not breech” rather than to 

FTP or fetal indication. 

Only 2 studies 

examined this. No 

evidence on race or 

ethnicity to determine if 

there is health disparity 

Multi-center prospective cohort study of eligible 

women for TOL. Measure rates of TOL and rates 

of ERCD along with predictors including race, 

ethnicity. 

Current prediction ability 

is low. 

Multi-center prospective cohort study of women 

eligible for TOL. Record TOL, ERCD and VBAC 

rates, Emergency CD rates. Measure effect of 

intervention predictors. 

6/6 cohort studies 

reported on neonatal 

death 

4of 6 cohort studies 

reported on maternal 

death 

- Multi-centered cohort 

- National registry of Uterine ruptures 

Limited data. Long-term follow-up study, beginning to follow 

women from their 1st CD, surveying them 

regarding future fertility, and follow for 30 to 40 

years. 

Limited data with uncombinable studies Large multicenter cohort utilizing standardized 

definition of endometritis as fever > x 24 hours 

post delivery requiring IV antibiotics. Other 

infectious morbidity should also be evaluated, but 

well defined, specifically x-ray confirmed 

pneumonia; wound infection defined as fever 

>100.5, with IV or PO antibiotics required; fever of 

unknown origin >48 hours. 

None Large multicenter study, which defines injury 

specifically by type/organ of injury: bladder; bowel; 

uterus (includes uterine artery laceration); cervix; 

3rd or 4th degree perineal laceration. Included in 

this should be length of surgery time as a marker 

for complexity of the case. 

Definitions are not 

consistent across studies, 

making it impossible to 

combine results & difficult 

to interpret data. 

Consensus conference to determine appropriate 

definitions. 

154 
Table 37. Future research 

Research Question 

Effect of study design on 

outcomes 

How does TOL versus 

ERCD effect 

breastfeeding initiation 

and continuation? 

What is the chance of 

VBAC when induction is 

required? 

What is the chance of 

uterine rupture when 

induction is required? 

How does the cumulative 

dose and regimen of 

induction agent (PGE2, 

oxytocin, etc.) affect 

maternal and infant 

harms? 

How does the cumulative 

dose and rate of infusion 

of oxytocin used for 

augmentation of labor 

affect infant and maternal 

harms? 

Domains Pertaining to Overall Strength of Evidence 

Results of Literature 

Review Types of Studies Needed to Answer Question 

This report found that 

studies differed 

substantially though not 

statistically significantly 

in their rates of uterine 

rupture based on study 

design (30/10,000 

versus 52/10,000 risk). 

This has large 

implications for what 

studies are sufficient to 

based clinical practice 

and policy. 

Conduct 2 cohort studies simultaneously keeping 

results blinded from other study - One that would 

define trial of labor and study only trial of labor 

patients and one that would consider the entire 

cohort of women with prior cesarean who have 

TOL versus ERCD 

No evidence Large cohort study 

Proportion with VBAC is 

54 percent to 69 

percent, depending on 

type of induction, but 

influence of 

confounding factors 

such as dose, prior VD, 

number of CDs not 

clear. 

RCT with power calculations to insure adequate 

numbers of subjects and planned univariate and 

multivariate regression analyses to examine 

impact of individual and combined potential 

confounding factors. 

Comparison group: expectant management 

Rate of rupture is 

estimated to be 1.2 

percent for all induction 

methods combined, 

however this is limited 

by the accuracy of the 

definition and 

ascertainment of 

rupture. 

RCT with power calculations to insure adequate 

numbers of subjects and planned univariate and 

multivariate regression analyses to examine 

impact of individual and combined potential 

confounding factors. 

Comparison group: expectant management. 

Uterine rupture must be defined and 

ascertainment methods should include chart 

review. 

Insufficient - RCT of women who are candidates for induction 

of TOL with 2 groups: induction or expectant 

management. 

Insufficient - RCT of women who are candidates for induction 

of TOL with 2 groups: induction or expectant 

management.. 

155 
Table 37. Future research 

Domains Pertaining to Overall Strength of Evidence 

Results of Literature 

Research Question Review Types of Studies Needed to Answer Question 

What are appropriate 

definitions for infant 

outcomes (death, 

respiratory, neurological)? 

Definitions are not 

consistent across 

studies, making it 

impossible to combine 

results & difficult to 

interpret data. 

Consensus conference to determine appropriate 

definitions. 

Abbreviations: CD=cesarean delivery; ERCD=elective repeat cesarean delivery; FTP=failure to progress; 

IV=intravenous; PGE=prostaglandin E2; PO=orally administered; RCT=randomized controlled trial; 

TOL=trial of labor; VBAC=vaginal birth after cesarean; VD=vaginal delivery 

156 
 

 

 

 

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second-trimester ultrasonography. Obstet 

Gynecol. 2005;105(5 Pt 1):962-965. 

Wu S, Kocherginsky M, Hibbard JU. Abnormal 

placentation: twenty-year analysis. Am J Obstet 

Gynecol. 2005;192(5):1458-1461. 

165 
 

 

 

 

257. Lynch CM, Kearney R, Turner MJ. Maternal 272. Boukerrou M, Lambaudie E, Collinet P, Crepin 

morbidity after elective repeat caesarean section G, Cosson M. A history of cesareans is a risk 

after two or more previous procedures. Eur J factor in vaginal hysterectomies. Acta Obstet 

Obstet Gynecol Reprod Biol. 2003;106(1):10-13. Gynecol Scand. 2003;82(12):1135-1139. 

258. Miller DA, Chollet JA, Goodwin TM. Clinical 273. David-Montefiore E, Rouzier R, Chapron C, 

risk factors for placenta previa-placenta accreta. Darai E, Collegiale d'Obstetrique et Gynecologie 

Am J Obstet Gynecol. 1997;177(1):210-214. de Paris-Ile de F. Surgical routes and 

259. Olive EC, Roberts CL, Algert CS, Morris JM. complications of hysterectomy for benign 

Placenta praevia: maternal morbidity and place of disorders: a prospective observational study in 

birth. Aust N Z J Obstet Gynaecol. French university hospitals. Hum Reprod. 

2005;45(6):499-504. 2007;22(1):260-265. 

260. Zelop CM, Harlow BL, Frigoletto FD, Jr., Safon 274. Myers SA, Bennett TL. Incidence of significant 

LE, Saltzman DH. Emergency peripartum adhesions at repeat cesarean section and the 

hysterectomy. Am J Obstet Gynecol. relationship to method of prior peritoneal closure. 

1993;168(5):1443-1448. J Reprod Med. 2005;50(9):659-662. 

261. Taylor VM, Kramer MD, Vaughan TL, Peacock 275. Tulandi T, Agdi M, Zarei A, Miner L, Sikirica V. 

S. Placenta previa and prior cesarean delivery: Adhesion development and morbidity after repeat 

how strong is the association? Obstet Gynecol. cesarean delivery. Am J Obstet Gynecol. 

1994;84(1):55-57. 2009;201(1):56.e51-56. 

262. Clark SL, Koonings PP, Phelan JP. Placenta 276. Al-Took S. Adhesion-related small-bowel 

previa/accreta and prior cesarean section. Obstet obstruction after gynecologic operations. Am J 

Gynecol. 1985;66(1):89-92. Obstet Gynecol. 1999;180(2):313-315. 

263. Macones GA, Cahill A, Pare E, et al. Obstetric 277. Bahl R, Strachan B, Murphy DJ. Outcome of 

outcomes in women with two prior cesarean subsequent pregnancy three years after previous 

deliveries: is vaginal birth after cesarean delivery operative delivery in the second stage of labour: 

a viable option? Am J Obstet Gynecol. cohort study. BMJ. 2004;328(7435):311. 

2005;192(4):1223-1228; discussion 1228-1229. 278. Murphy DJ, Stirrat GM, Heron J, Team AS. The 

264. Grubb DK, Kjos SL, Paul RH. Latent labor with relationship between Caesarean section and 

an unknown uterine scar. Obstet Gynecol. subfertility in a population-based sample of 14 

1996;88(3):351-355. 541 pregnancies. Hum Reprod. 2002;17(7):1914-

265. Lin C, Raynor BD. Risk of uterine rupture in 1917. 

labor induction of patients with prior cesarean 279. Cramer DW, Xu H, Harlow BL. Does "incessant" 

section: an inner city hospital experience. Am J ovulation increase risk for early menopause? Am 

Obstet Gynecol. 2004;190(5):1476-1478. J Obstet Gynecol. 1995;172(2 Pt 1):568-573. 

266. Tahilramaney MP, Boucher M, Eglinton GS, 280. Bahtiyar MO, Julien S, Robinson JN, et al. Prior 

Beall M, Phelan JP. Previous cesarean section cesarean delivery is not associated with an 

and trial of labor. Factors related to uterine increased risk of stillbirth in a subsequent 

dehiscence. J Reprod Med. 1984;29(1):17-21. pregnancy: analysis of U.S. perinatal mortality 

267. Bujold E, Hammoud A, Schild C, Krapp M, data, 1995-1997. Am J Obstet Gynecol. 

Baumann P. The role of maternal body mass 2006;195(5):1373-1378. 

index in outcomes of vaginal births after 281. Smith GCS, Pell JP, Dobbie R. Caesarean section 

cesarean. Am J Obstet Gynecol. and risk of unexplained stillbirth in subsequent 

2005;193(4):1517-1521. pregnancy. Lancet. 2003;362(9398):1779-1784. 

268. Carroll CS, Sr., Magann EF, Chauhan SP, 282. Bujold E, Francoeur D. Neonatal morbidity and 

Klauser CK, Morrison JC. Vaginal birth after decision-delivery interval in patients with uterine 

cesarean section versus elective repeat cesarean rupture.[comment]. J Obstet Gynaecol Can. 

delivery: Weight-based outcomes. Am J Obstet 2005;27(7):671-673; author reply 673. 

Gynecol. 2003;188(6):1516-1520; discussion 283. Paterson CM, Saunders NJ. Mode of delivery 

1520-1512. after one caesarean section: audit of current 

269. Edwards RK, Harnsberger DS, Johnson IM, practice in a health region. BMJ. 

Treloar RW, Cruz AC. Deciding on route of 1991;303(6806):818-821. 

delivery for obese women with a prior cesarean 284. Richardson BS, Czikk MJ, daSilva O, Natale R. 

delivery. Am J Obstet Gynecol. 2003;189(2):385- The impact of labor at term on measures of 

389; discussion 389-390. neonatal outcome. Am J Obstet Gynecol. 

270. Hamel KJ. Incidence of adhesions at repeat 2005;192(1):219-226. 

cesarean delivery. Am J Obstet Gynecol. 285. The World Factbook 2008. Washington, D. C.: 

2007;196(5):e31-32. Central Intelligence Agency; 2008. 

271. Ogunyemi D, Hullett S, Leeper J, Risk A. 286. Kamath BD, Todd JK, Glazner JE, Lezotte D, 

Prepregnancy body mass index, weight gain Lynch AM. Neonatal outcomes after elective 

during pregnancy, and perinatal outcome in a cesarean delivery. Obstet Gynecol. 

rural black population. J Matern Fetal Med. 2009;113(6):1231-1238. 

1998;7(4):190-193. 

166 
 

287. Warren J, Anderson JM. Respiratory Distress in 290. Brown P. How to formulate research 

the Term Infant: A Review. [in press]. recommendations. BMJ. 2006;333(14):804-806. 

Pediatrics. 2009. 291. Ecker JL. Once a pregnancy, always a cesarean? 

288. Hankin G, Speer M. Defining the pathogenesis Rationale and feasibility of a randomized 

and pathophysiology of neonatal encephalopathy controlled trial. . Am J Obstet Gynecol. 

and cerebral palsy. Obstet Gynecol. 2004;190(2):314-318. 

2003;102(3):628-636. 

289. Committee on Fetus and Newborn. Levels of 

Neonatal Care. Pediatrics. 2004;114(5):1341-

1347. 

167 
CI 

Abbreviations and Acronyms 

ACOG American College of Obstetricians and Gynecologists 

AUROC Area Under the Receiver Operating Characteristic curve 

AHRQ Agency for Healthcare Research and Quality 

AAP American Academy of Pediatrics 

BMI Body mass index 

CDC Centers for Disease Control and Prevention 

Confidence interval 

DARE Database of Abstracts of Reviews of Effectiveness 

EPC Evidence-based Practice Center 

ERCD Elective repeat cesarean delivery 

FDA Food and Drug Administration 

FHR Fetal heart rate 

FMR Fetal mortality rate 

FTP Failure to progress 

GA Gestational age 

HCUP Healthcare Cost and Utilization Project 

HIE Hypoxic-ischemic encephalopathy 

HMO Health Maintenance Organizations 

I/A Induction/augmentation 

ICD-9 International Classification of Diseases, 9th Edition/Revision 

ICU Intensive care unit 

IOL Induction of labor 

IRB Institutional review board 

IRCD Indicated repeat cesarean delivery 

IUFD Intrapartum fetal demise 

kg Kilograms 

LTCD Low transverse cesarean delivery 

National Institute of Child Health and Human Development Maternal-Fetal Medicine 

MFMU Units 

mL Milliliters 

mm Millimeters 

NICU Neonatal intensive care unit 

NIH National Institutes of Health 

NMR Neonatal mortality rate 

NNH Number needed to harm 

NS Not significant 

OMAR National Institutes of Health Office of Medical Applications of Research 

OECD Organization for Economic Cooperation and Development 

OR Odds ratio 

PGE2 prostaglandin E2 

PMR Perinatal mortality rate 

RCD Repeat cesarean delivery 

RCT Randomized controlled trial 

RD Risk difference 

RDS Respiratory distress syndrome 

ROC Receiver operating characteristic 

169
 
Abbreviations and Acronyms 

ROM Rupture of the membranes 

RR Relative risk 

TEP Technical expert panel 

TTN Transient tachypnea of the newborn 

UK United Kingdom 

US United States of America 

USPSTF US Preventive Services Task Force 

VBAC Vaginal birth after cesarean section 

wk Week(s) 

170
 
 

 

Appendix A. Technical Expert Panel Members 

Technical Expert Panel Members

Eugene Declercq, Ph.D. 

Assistant Dean, Doctoral Education Professor, Department of Community Health Sciences at Boston 

University 

Stanley Ip, M.D. 

Investigator, TUFTS University Evidence-based Practice Center at New England Medical Center 

Amelia Psmythe 

Executive Director, Nursing Mothers Counsel of Oregon 

Carol Sakala, Ph.D., M.S.P.H. 

Director of Programs with Childbirth Connections. 

John M. Thorp, Jr., M.D. 

Division Director, Professor Adjunct Professor in the Department of Obstetrics and Gynecology at the 

University of North Carolina 

Linda J. Van Marter, M.D., M.P.H. 

Associate Professor of Pediatrics at Harvard Medical School, Children's Hospital 

Professional Organization Representation 

American Academy of Family Physicians 

Represented by: Lesley Atwood, M.D. 

American Academy of Pediatrics 

Represented by: Allen Merritt, M.D., M.P.A:HA 

American College of Nurse-Midwives 

Represented by: Mary Barger, C.N.M., M.P.H. 

American College of Obstetricians and Gynecologists 

Represented by: Carolyn Zelop, M.D. 

A-1 
 

 

Appendix B. Expert Reviewers 

Individuals 

Eugene Declercq, Ph.D. 

Assistant Dean, Doctoral Education Professor, Department of Community Health Sciences at Boston 

University 

William Grobman, M.D., M.B.A. 

Assistant Professor of Obstetrics and Gynecology, Section of Maternal-Fetal Medicine, 

Department of Obstetrics and Gynecology, Assistant Professor of Preventative Medicine, Department of 

Preventative Medicine, Northwestern University Medical School 

Stanley Ip, M.D. 

Investigator, TUFTS University Evidence-based Practice Center at New England Medical Center 

Diana Petitti, M.D., M.P.H. 

Professor of Biomedical Informatics at Arizona State University 

Amelia Psmythe 

Executive Director, Nursing Mothers Counsel of Oregon 

Carol Sakala, Ph.D., M.S.P.H. 

Director of Programs with Childbirth Connections. 

James Scott, M.D. 

Professor of Obstetrics and Gynecology in the School of Medicine at the University of Utah and Editor of 

the Green Journal 

Professional Organization Representation

American Academy of Family Physicians 

Represented by: Eric Wall, M.D., FAAFP; Senior Medical Director of Qualis Health 

American College of Nurse-Midwives 

Represented by: Nancy Lowe, C.N.M., Ph.D.; Professor of Nurse-Midwifery in the college of Nursing at 

the University of Colorado Denver 

American College of Obstetricians and Gynecologists 

Represented by: Carolyn Zelop, M.D.; St. Francis Care, Department of Maternal Fetal Medicine 

B-2 
Appendix B. Expert Reviewers, continued 

Federal Reviewers 

Suzanne Haynes, Ph.D. 

Senior Science Advisor, Office on Women’s Health, US Department of Health and Human Services 

Mark Klebanoff, M.D., M.P.H. 

Senior Investigator, National Institute of Child Health and Human Development, Epidemiology (EPI) 

Branch 

Miriam Kuppermann, Ph.D., M.P.H. 

Professor in the Department of Obstetrics, Gynecology & Reproductive Sciences at the University of 

California, San Francisco 

Susan Meikle, M.D., M.S.P.H. 

Contraception & Reproductive Health (CRH) Branch, National Institute of Child Health and Human 

Development, Contraception & Reproductive Health (CRH) Branch 

Jun Zhang, M.D., Ph.D. 

Senior Investigator, National Institute of Child Health and Human Development, Epidemiology (EPI) 

Branch 

B-3 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix C. Search Strategies 

Core Search 

Database: Ovid MEDLINE(R) <1950 to August Week 4 2009> 

1 exp Vaginal Birth after Cesarean/ (856) 

2 vbac.mp. (264) 

3 (vagina$ adj3 (birth$ or born or deliver$) adj7 ((after$ or follow$ or previous$ or prior or history) adj3 

(cesarean$ or caesarean$))).mp. [mp=title, original title, abstract, name of substance word, subject 

heading word] (1448) 

4 1 or 3 or 2 (1470) 

5 exp "Trial of Labor"/ (682) 

6 (trial of labor or trial of labour).mp. [mp=title, original title, abstract, name of substance word, subject 

heading word] (937) 

7 tol.mp. (949) 

8 6 or 7 (1833) 

9 exp pregnancy/ or exp pregnancy complications/ (654827) 

10 exp Infant, Newborn/ (429340) 

11 exp Obstetrics/ (13288) 

12 exp Obstetric Surgical Procedures/ (89545) 

13 11 or 10 or 9 or 12 (981159) 

14 8 and 13 (947) 

15 14 or 5 (947) 

16 exp Cesarean Section, Repeat/ (395) 

17 ((repeat$ or multip$ or another or prior or previous$) adj3 (cesarean$ or caesarean$)).mp. [mp=title, 

original title, abstract, name of substance word, subject heading word] (2585) 

18 ((second or third) adj cesarean).mp. [mp=title, original title, abstract, name of substance word, 

subject heading word] (30) 

19 16 or 17 or 18 (2601)
 

20 4 or 19 or 15 (3607) 

21 limit 20 to (english language and humans) (2888) 

Database: EBM Reviews - Cochrane Central Register of Controlled Trials <3rd Quarter 2009> 

1 vbac.mp. (6) 

2 (vagina$ adj3 (birth$ or born or deliver$) adj7 ((after$ or follow$ or previous$ or prior or history) adj3 

(cesarean$ or caesarean$))).mp. [mp=title, original title, abstract, mesh headings, heading words, 

keyword] (14) 

3 1 or 2 (17) 

4 (trial of labor or trial of labour).mp. [mp=title, original title, abstract, mesh headings, heading words, 

keyword] (38) 

5 tol.mp. (16) 

6 4 or 5 (53) 

7 ((repeat$ or multip$ or another or prior or previous$) adj3 (cesarean$ or caesarean$)).mp. [mp=title, 

original title, abstract, mesh headings, heading words, keyword] (113) 

8 ((second or third) adj cesarean).mp. [mp=title, original title, abstract, mesh headings, heading words, 

keyword] (1) 

9 7 or 8 (113) 

10 6 or 3 or 9 (160) 

Database: EBM Reviews - Cochrane Database of Systematic Reviews <1st Quarter 2009> 

1 vbac.mp. (4) 

2 (vagina$ adj3 (birth$ or born or deliver$) adj7 ((after$ or follow$ or previous$ or prior or history) adj3 

(cesarean$ or caesarean$))).mp. [mp=title, abstract, full text, keywords, caption text] (15) 

3 1 or 2 (16) 

4 (trial of labor or trial of labour).mp. [mp=title, abstract, full text, keywords, caption text] (13) 

5 tol.mp. (2) 

6 4 or 5 (15) 

C-1 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix C. Search Strategies, continued 

7 ((repeat$ or multip$ or another or prior or previous$) adj3 (cesarean$ or caesarean$)).mp. [mp=title, 

abstract, full text, keywords, caption text] (65) 

8 ((second or third) adj cesarean).mp. [mp=title, abstract, full text, keywords, caption text] (0) 

9 7 or 8 (65) 

10 6 or 3 or 9 (72)
 

Database: EBM Reviews - Database of Abstracts of Reviews of Effects <3rd Quarter 2009> 

1 vbac.mp. (2) 

2 (vagina$ adj3 (birth$ or born or deliver$) adj7 ((after$ or follow$ or previous$ or prior or history) adj3 

(cesarean$ or caesarean$))).mp. [mp=title, full text, keywords] (1) 

3 1 or 2 (3) 

4 (trial of labor or trial of labour).mp. [mp=title, full text, keywords] (8) 

5 tol.mp. (3) 

6 4 or 5 (9) 

7 ((repeat$ or multip$ or another or prior or previous$) adj3 (cesarean$ or caesarean$)).mp. [mp=title, 

full text, keywords] (17) 

8 ((second or third) adj cesarean).mp. [mp=title, full text, keywords] (0) 

9 7 or 8 (17) 

Uterine Rupture Specific Search 

Database: Ovid MEDLINE(R) <1950 to August Week 4 2009> 

1 exp Vaginal Birth after Cesarean/ (858) 

2 vbac.mp. (266) 

3 (vagina$ adj3 (birth$ or born or deliver$) adj7 ((after$ or follow$ or previous$ or prior or history) adj3 

(cesarean$ or caesarean$))).mp. [mp=title, original title, abstract, name of substance word, subject 

heading word] (1450) 

4 1 or 3 or 2 (1473) 

5 exp "Trial of Labor"/ (682) 

6 (trial of labor or trial of labour).mp. [mp=title, original title, abstract, name of substance word, subject 

heading word] (937) 

7 tol.mp. (949) 

8 6 or 7 (1833) 

9 exp pregnancy/ or exp pregnancy complications/ (655357) 

10 exp Infant, Newborn/ (429611) 

11 exp Obstetrics/ (13301) 

12 exp Obstetric Surgical Procedures/ (89607) 

13 11 or 10 or 9 or 12 (981885) 

14 8 and 13 (947) 

15 14 or 5 (947) 

16 exp Cesarean Section, Repeat/ (396) 

17 ((repeat$ or multip$ or another or prior or previous$) adj3 (cesarean$ or caesarean$)).mp. [mp=title, 

original title, abstract, name of substance word, subject heading word] (2587) 

18 ((second or third) adj cesarean).mp. [mp=title, original title, abstract, name of substance word, 

subject heading word] (30) 

19 16 or 17 or 18 (2603)
 

20 4 or 19 or 15 (3610) 

21 limit 20 to (english language and humans) (2891) 

22 ((uterine or uterus) adj5 (ruptur$ or tear$ or torn or perforat$ or lacerat$ or trauma$ or damag$ or
 

injur$)).mp. (5413) 

23 22 and 21 (611) 

Obesity Specific Search 

Database: Ovid MEDLINE(R) <1950 to August Week 4 2009> 

C-2 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix C. Search Strategies, continued 

1 exp Vaginal Birth after Cesarean/ (858) 

2 vbac.mp. (266) 

3 (vagina$ adj3 (birth$ or born or deliver$) adj7 ((after$ or follow$ or previous$ or prior or history) adj3 

(cesarean$ or caesarean$))).mp. [mp=title, original title, abstract, name of substance word, subject 

heading word] (1450) 

4 1 or 3 or 2 (1473) 

5 exp "Trial of Labor"/ (682) 

6 (trial of labor or trial of labour).mp. [mp=title, original title, abstract, name of substance word, subject 

heading word] (937) 

7 tol.mp. (949) 

8 6 or 7 (1833) 

9 exp pregnancy/ or exp pregnancy complications/ (655357) 

10 exp Infant, Newborn/ (429611) 

11 exp Obstetrics/ (13301) 

12 exp Obstetric Surgical Procedures/ (89607) 

13 11 or 10 or 9 or 12 (981885) 

14 8 and 13 (947) 

15 14 or 5 (947) 

16 exp Cesarean Section, Repeat/ (396) 

17 ((repeat$ or multip$ or another or prior or previous$) adj3 (cesarean$ or caesarean$)).mp. [mp=title, 

original title, abstract, name of substance word, subject heading word] (2587) 

18 ((second or third) adj cesarean).mp. [mp=title, original title, abstract, name of substance word, 

subject heading word] (30) 

19 16 or 17 or 18 (2603)
 

20 4 or 19 or 15 (3610) 

21 limit 20 to (english language and humans) (2891) 

22 exp Obesity/ (91434) 

23 body weight/ or exp body weight changes/ or exp overweight/ or thinness/ (239228) 

24 exp "Body Weights and Measures"/ (322374) 

25 22 or 24 or 23 (342869) 

26 21 and 25 (207) 

Multiple Cesarean Specific Search 

Database: Ovid MEDLINE(R) <1950 to October Week 4 2009> 

1 exp Cesarean Section, Repeat/ (429) 

2 ((repeat$ or multip$ or another) adj3 cesarean).mp. (1041) 

3 ((second or third) adj cesarean).mp. (32) 

4 3 or 1 or 2 (1061) 

5 limit 4 to (english language and humans) (855) 

6 limit 5 to yr="1980 -Current" (833) 

7 4 not 1 (632) 

8 limit 1 to (english language and humans and yr="1980 -Current") (364) 

9 exp "Outcome and Process Assessment (Health Care)"/ (471672) 

10 exp Postoperative Complications/ (344232) 

11 (ae or co).fs. (2302892) 

12 11 or 10 or 9 (2833102) 

13 ((repeat$ or multip$ or another or subsequent$ or previous$ or prior) adj3 cesarean).mp. (2237) 

14 3 or 13 (2254) 

15 12 and 14 (910) 

16 limit 15 to (english language and humans and yr="1980 -Current") (716) 

17 16 not 8 (535) 

18 9 and 14 (107) 

19 limit 18 to (english language and humans and yr="1980 -Current") (96)
 

20 19 not 8 (75) 

21 17 not 20 (460) 

C-3 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix C. Search Strategies, continued 

22 from 21 keep 1-460 (460) 

Background Questions Specific Search 

Database: Ovid MEDLINE(R) <1950 to October Week 1 2009> 

1 exp Vaginal Birth after Cesarean/ (888) 

2 vbac.mp. (275) 

3 (vagina$ adj3 (birth$ or born or deliver$) adj7 ((after$ or follow$ or previous$ or prior or history) adj3 

cesarean)).mp. (1347) 

4 1 or 2 or 3 (1374) 

5 exp "Trial of Labor"/ (691) 

6 (trial adj2 labor).mp. (927) 

7 tol.mp. (984) 

8 6 or 7 (1856) 

9 exp pregnancy/ or exp pregnancy complications/ (655043) 

10 exp Infant, Newborn/ (431654) 

11 exp Obstetrics/ (13439) 

12 exp Obstetric Surgical Procedures/ (89191) 

13 9 or 10 or 11 or 12 (985177) 

14 8 and 13 (938) 

15 5 or 14 (938) 

16 exp Cesarean Section, Repeat/ (428) 

17 ((repeat$ or multip$ or another) adj3 cesarean).mp. (1039) 

18 ((second or third) adj cesarean).mp. (32) 

19 18 or 16 or 17 (1059)
 

20 4 or 19 or 15 (2507) 

21 exp LEGISLATION as topic/ (55190) 

22 exp JURISPRUDENCE/ (137951) 

23 lj.fs. (171704) 

24 22 or 21 or 23 (295921) 

25 24 and 20 (68)
 

26 exp bioethical issues/ (3229) 

27 exp bioethics/ (8140) 

28 (ethic$ or bioethic$).mp. [mp=title, original title, abstract, name of substance word, subject heading 

word, unique identifier] (106986) 

29 27 or 28 or 26 (106986) 

30 29 and 20 (22)
 

31 exp human rights/ (97424) 

32 31 and 20 (36)
 

33 25 or 32 or 30 (95) 

34 Physician's Practice Patterns/ (29292) 

35 20 and 34 (55)
 

36 exp Attitude to Health/ (216292) 

37 20 and 36 (138) 

38 exp Economics/ (415371) 

39 ec.fs. (262834) 

40 38 or 39 (490853) 

41 20 and 40 (112) 

42 exp Decision Making/ (86984) 

43 20 and 42 (93)
 

44 exp Counseling/ (26819) 

45 20 and 44 (14)
 

46 "attitude of health personnel"/ or refusal to treat/ (75034) 

47 20 and 46 (32)
 

48 exp Health Services Accessibility/ (64701) 

49 20 and 48 (6) 

C-4 
 

 

 

 

 

 

 

 

Appendix C. Search Strategies, continued 

50 exp "Health Services Needs and Demand"/ (36937) 

51 20 and 50 (5) 

52 exp Social Control Policies/ (94601) 

53 20 and 52 (16)
 

54 exp Hospital Administration/ (183749) 

55 20 and 54 (35)
 

56 35 or 33 or 53 or 51 or 41 or 47 or 49 or 37 or 45 or 43 or 55 (424) 

57 from 56 keep 1-424 (424) 

C-5 
Appendix D. List of Developed Countries 

Excerpt from CIA World Factbook 20081 

Developed Countries: 

The top group in the hierarchy of developed countries (DCs), former USSR/Eastern Europe (former 

USSR/EE), and less developed countries (LDCs); includes the market-oriented economies of the mainly 

democratic nations in the Organization for Economic Cooperation and Development (OECD), Bermuda, 

Israel, South Africa, and the European ministates; also known as the First World, high-income countries, 

the North, industrial countries; generally have a per capita GDP in excess of $10,000 although four 

OECD countries and South Africa have figures well under $10,000 and two of the excluded OPEC 

countries have figures of more than $10,000. 

The 34 DCs are: 

Andorra 

Australia 

Austria 

Belgium 

Bermuda 

Canada 

Denmark 

Faroe Islands 

Finland 

France 

Germany 

Greece 

Holy See 

Iceland 

Ireland 

Israel 

Italy 

Japan 

Liechtenstein 

Luxembourg 

Malta 

Monaco 

Netherlands 

NZ 

Norway 

Portugal 

San Marino 

South Africa 

Spain, Sweden 

Switzerland 

Turkey 

UK 

US 

1. The World Factbook 2008. Washington, D. C.: Central Intelligence Agency; 2008. 

D-1 
Appendix E. Inclusion and Exclusion Criteria 

Abstract Review Coding 

Inclusions 

•	 IN for a specific key question or topic area 

•	 Background for general, question 1 or question 2 

Exclusions 

• No data 

•	 Wrong Population (animal study, abortion, multiple gestations, etc) 

•	 Opinion or Letter with No Data 

•	 No previous cesarean 

• Developing country 

Full-Text Paper Review Coding 

Inclusions 

•	 IN for a specific key question or topic area 

•	 In, but no comparator 

•	 Background for general, question 1 or question 2 

Exclusions 

•	 No data for topic 

•	 Wrong Population (specify reason: no previous cesarean, animal study, abortion, multiple 

gestations, pre-existing medical condition, pre-term (<37 weeks), cadavers, etc) 

•	 No full-text paper or Opinion or Letter with No Data 

•	 Cannot isolate our population of interest (specify reason) 

•	 Developing country/Not in English 

•	 < 10 subjects 

•	 Study began or published before 1980 

•	 Insufficient to determine population 

E-1 
Appendix F. Excluded Studies List 

Exclusion codes key: 

Code Reason 

4 No data for topic 

5 Wrong Population (specify reason: no previous cesarean, animal study, abortion, 

multiple gestations, pre-existing medical condition, pre-term (<37 weeks), cadavers, etc) 

6 No full-text paper, opinion or letter with no data 

7 Cannot isolate our population of interest (specify reason) 

8 Developing country/Not in English 

9 Less than 10 subjects 

10 Study began or published before 1980 

11 Insufficient to determine population 

List of studies: 

1. Vaginal delivery after cesarean 

section. Am Fam Physician, 1985. 

32(3): p. 90. 

Exclusion code: 6 

2. Cesarean births and trial of labor 

rates. Jama, 1987. 257(20): p. 2757-

9. 

Exclusion code: 6 

3. A method of predicting the likelihood 

of success or failure in a trial of 

labor in any given set of 

circumstances is a laudable 

goal.[comment]. J Reprod Med, 

1991. 36(11): p. 829-31. 

Exclusion code: 4 

4. Nonclinical factors and repeat Csection.[comment]. Jama, 1991. 

265(18): p. 2338-9. 

Exclusion code: 6 

5. Improving the timeliness of 

emergency C-sections at 

Southwestern Vermont Medical 

Center leads to improved patient 

care and increased physician 

satisfaction. Qual Lett Healthc Lead, 

1993. 5(1): p. 6-8. 

Exclusion code: 6 

6. Repeat cesarean section vs. VBACs: 

helping women decide. AWHONN 

Voice, 1994. 2(8): p. 1. 

Exclusion code: 6 

7. Trial of labor vs. elective repeat 

cesarean section. AAFP Task Force 

on Clinical Policies for Patient Care. 

Am Fam Physician, 1995. 52(6): p. 

1763-5. 

Exclusion code: 4 

8. Vaginal delivery after a previous 

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opinion. Number 143-October 1994 

(replaces No. 64, October 1988). 

Committee on Obstetric Practice. 

American College of Obstetricians 

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Exclusion code: 4 

9. ACOG releases practice guidelines 

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1996. 53(2): p. 775-6. 

Exclusion code: 6 

10. Vaginal delivery after previous 

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F-1 
Appendix F. Excluded Studies List, continued 

Patterns. American College of 

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J Gynaecol Obstet, 1996. 52(1): p. 

90-8. 

Exclusion code: 4 

11. VBAC (vaginal birth after 

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Hosp Case Manag, 1996. 4(11): p. 

161-4. 

Exclusion code: 6 

12. What is the right number of 

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13. Case records of the Massachusetts 

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Exclusion code: 9 

14. Outreach program slashes Florida 

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Exclusion code: 6 

15. Stats & facts. Vaginal births after 

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Exclusion code: 4 

16. Medical discipline--not guilty. N Z 

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following U755. 

Exclusion code: 6 

17. National Institutes of Health state-ofthe-science conference statement: 

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Exclusion code: 4 

18. NIH State of the Science Conference: 

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Exclusion code: 4 

19. Risks and benefits of caesarean 

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20. Aali, B.S. and B. Motamedi, 

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21. Abbas, F., et al., Placenta percreta 

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22. Abboud, T.K., et al., Isoflurane or 

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23. Abboud, T.K., et al., Isoflurane or 

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F-2 
Appendix F. Excluded Studies List, continued 

1989. 33(7): p. 578-81. 

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24. Abboud, T.K., et al., Desflurane: a 

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25. Abboud, T.K., et al., Intravenous 

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26. Abdelhak, Y.E., et al., Management 

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27. Abitbol, M.M., et al., The 

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28. Abouleish, E., et al., Combined 

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29. Aboulfalah, A., et al., Induction of 

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42. 

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30. Abu-Ghazzeh, Y.M. and R. Barqawi, 

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31. Abu-Heija, A.T. and A.M. Ali, 

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32. Abu-Heija, A.T., F. El-Jallad, and S. 

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33. Afriat, C.I., Vaginal birth after 

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34. Agostini, A., et al., Risk of bladder 

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35. Al Nuaim, L.A., S. Kattan, and M.S. 

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F-3 
Appendix F. Excluded Studies List, continued 

36. Al Sakka, M., W. Dauleh, and S. Al 

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37. Al Sakka, M., A. Hamsho, and L. 

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38. Alarab, M., et al., Singleton vaginal 

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39. Albers, L.L., Safety of VBACs in 

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40. Alexander, J.M., et al., Fetal injury 

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41. Alexiadis, G., et al., Abdominal wall 

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42. Alfirevic, Z., Oral misoprostol for 

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43. Alfirevic, Z. and A. Weeks, Oral 

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44. Algert, C.S., et al., Labor before a 

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45. Al-Kadri, H., et al., Failed individual 

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46. Alkatib, M., A.V.M. Franco, and 

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47. Almeida, E.C.S., et al., Cesarean 

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48. Al-Najjar, F.S. and A.M. Al-Shafiai, 

F-4 
Appendix F. Excluded Studies List, continued 

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49. Alran, S., et al., Maternal and 

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50. Altman, D., et al., Symptoms of anal 

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51. Al-Took, S., Adhesion-related smallbowel obstruction after gynecologic 

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52. Amon, E., B.M. Sibai, and G.D. 

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53. Andersen, H.F., et al., Neonatal 

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54. Andersen, J.R., et al., Decidual 

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55. Anderson, G. and C. Strong, The 

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56. Andrews, W.W., et al., Effect of type 

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57. Angelini, D.J. and L. Greenwald, 

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58. Annibale, D.J., et al., Comparative 

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59. Anteby, S.O., A. Birkenfeld, and D. 

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60. Antoine, C. and B.K. Young, Fetal 

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61. Appleton, B., et al., Knowledge and 

F-5 
Appendix F. Excluded Studies List, continued 

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62. Ardiet, E., D. Subtil, and F. Puech, 

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63. Arias, E., et al., Annual summary of 

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64. Armstrong, V., et al., Detection of 

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65. Arraztoa, J.A., et al., [Delivery 

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66. Arulkumaran, S., et al., Uterine 

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67. Arulkumaran, S., I. Ingemarsson, 

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68. Ash, A., A. Smith, and D. Maxwell, 

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69. Ashton, P., et al., Return to theatre--

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70. Asole, S., et al., Effect of hospital 

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71. Atad, J., et al., Ripening and 

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72. Atad, J., et al., Continuous 

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73. Atalla, R.K., et al., Reactive 

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F-6 
Appendix F. Excluded Studies List, continued 

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74. Atug, F., et al., Delivery of dead 

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75. Austin, S.E., Childbirth classes for 

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76. Avery, J.K., Loss prevention case of 

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77. Avery, J.K., The obstetrical 

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78. Bader, D., et al., Breathing patterns 

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79. Bai, S.W., et al., Peripartum 

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52. 

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80. Bainbridge, J., Choices after 

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6. 

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81. Bakshi, S. and B.A. Meyer, 

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82. Barker, G., et al., Placental water 

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Exclusion code: 4 

83. Barnsley, J.M., et al., Cesarean 

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84. Barton, D.P., M.J. Turner, and J.M. 

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85. Baskett, T.F., Emergency obstetric 

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86. Baskett, T.F., Uterine compression 

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87. Basson, E., H.J. Odendaal, and D. 

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Afrikaanse Tydskrif Vir 

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88. Beall, M., et al., Vaginal delivery 

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89. Beckett, V.A. and L. Regan, Vaginal 

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90. Ben Nagi, J., et al., Reproductive 

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91. Ben Shachar, I. and D. Weinstein, 

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92. Benedetti, T.J., L. Platt, and M. 

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93. Ben-Haroush, A., et al., Indicated 

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94. Ben-Haroush, A., et al., Accuracy of 

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95. Benterud, T., Cesarean section is 

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61. 

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96. Berard, J., et al., Fetal macrosomia: 

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97. Berg, C.J., et al., Overview of 

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98. Bergeron, M.-E., et al., Sonography 

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99. Bergholt, T., et al., Prevalence and 

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F-8 
Appendix F. Excluded Studies List, continued 

16(11): p. 2418-21. 

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100. Bergholt, T., et al., Intraoperative 

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101. Berglund, L. and O. Axelsson, 

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102. Bernstein, P., Prostaglandin E2 gel 

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Can Med Assoc J 1992 Apr 

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103. Bhal, P.S., A. Sharma, and K. Asaad, 

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104. Bhattacharjee, N., R.P. Ganguly, and 

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5. 

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105. Biasucci, G., et al., Cesarean 

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106. Binder, T., et al., Conducting labor 

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107. Bingham, P., V. Hird, and R.J. 

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108. Biswas, A., Management of previous 

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109. Bjelic-Radisic, V., et al., Neonatal 

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110. Black, C., J.A. Kaye, and H. Jick, 

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111. Blackwell, S.C., et al., Influence of 

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F-9 
Appendix F. Excluded Studies List, continued 

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112. Blanchette, H., Comparison of 

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113. Blumenthal, N.J., et al., Changing 

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Exclusion code: 7 

114. Bolaji, I.I. and F.P. Meehan, 

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Exclusion code: 10 

115. Bolaji, I.I. and F.P. Meehan, Post 

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51(3): p. 181-92. 

Exclusion code: 4 

116. Bossert, R., et al., Early postpartum 

discharge at a university hospital. 

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Exclusion code: 4 

117. Boucher, M., et al., Maternal 

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after previous cesarean delivery. A 

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1984. 29(1): p. 12-6. 

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118. Boulet, S.B., Macrosomic births in 

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119. Boulet, S.L., H.M. Salihu, and G.R. 

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120. Boulvain, M., et al., Trial of labour 

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J Obstet Gynaecol, 1997. 104(12): p. 

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121. Boulvain, M., A.J. Kelly, and O. 

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122. Boulvain, M., C. Stan, and O. Irion, 

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Exclusion code: 4 

123. Bowers, S.K., H.M. MacDonald, and 

E.D. Shapiro, Prevention of 

iatrogenic neonatal respiratory 

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124. Bradley, C.F., S.E. Ross, and J. 

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125. Brahams, D., Caesarean sections by 

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126. Bricker, L. and M. Luckas, 

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127. Brill, Y., et al., The management of 

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128. Brill, Y. and R. Windrim, Vaginal 

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129. Brink, S., C-sections rise but may 

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130. Brody, C.Z., et al., Vaginal birth 

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131. Brown, C.E., et al., Puerperal septic 

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132. Brubaker, L., Outcomes of trial of 

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133. Bucklin, B.A., Vaginal birth after 

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134. Buechner, J.S., Rate of vaginal births 

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135. Buist, R., J. Brown, and T. 

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136. Bujold, E., Uterine rupture and 

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137. Bujold, E., A. Hammoud, and I. 

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144. Cahill, A.G., et al., Risk factors for 

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146. Cakmak, H. and S. Kuguoglu, 

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150. Caron, A. and D. Neuhauser, The 

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151. Carpenter, M.W., et al., Practice 

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152. Carr, C.A., P. Burkhardt, and M. 

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155. Cesario, S.K., Reevaluation of 

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156. Chadha, Y.C., et al., Breech delivery 

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157. Chaim, W., et al., Prevalence and 

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158. Chang, C., Trial of labor with prior 

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159. Chang, C.-Y., et al., Preservation of 

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160. Chanrachakul, B., S. Hamontri, and 

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161. Chattopadhyay, K., et al., Vaginal 

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162. Chattopadhyay, S.K., H. Kharif, and 

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163. Chattopadhyay, S.K., M.M. 

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164. Chauhan, S.P., et al., Application of 

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166. Chauhan, S.P., et al., Neonatal 

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167. Chazotte, C. and W.R. Cohen, 

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168. Chelmow, D. and R.K. Laros, Jr., 

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169. Chen, H.Y., S.J. Chen, and F.J. 

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170. Chen, K.C. and T.T. Hsieh, Rupture 

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171. Chen, L.H., K.H. Tan, and G.S. Yeo, 

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172. Cheng, M. and M. Hannah, Breech 

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173. Chestnut, D.H., Does epidural 

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174. Cheung, V.Y.T., Sonographic 

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175. Chez, R.A., Cervical ripening and 

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176. Chigbu, C.O., J.O. Enwereji, and 

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177. Cho, M.K., Y.H. Kim, and T.B. 

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178. Christian, S.S., et al., Vaginal breech 

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179. Chua, S. and S. Arulkumaran, Trial 

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180. Chuang, J.H. and R.A. Jenders, Trial 

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181. Chung, A., et al., Cost-effectiveness 

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182. Cicinelli, E., et al., Predictive factors 

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183. Clark, S.L., Rupture of the scarred 

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184. Clark, S.L., et al., Reducing obstetric 

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185. Clark, S.L., P.P. Koonings, and J.P. 

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186. Clark, S.L., et al., Is vaginal birth 

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187. Clark, S.L., et al., Emergency 

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F-15 
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189. Clarke, S.C. and S.M. Taffel, State 

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190. Clarkson, C., D.C. Derrick, and M. 

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191. Clarkson, C. and M. Newburn, 

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192. Clarkson, C. and M. Newburn, 

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194. Cohain, J.S., Vaginal births after Csection are not necessarily riskier in 

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195. Cohain, J.S., VBAC rupture & birth 

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196. Cohain, J.S. and S. Bewley, Vaginal 

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197. Coleman, V.H., et al., Vaginal birth 

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199. Collins, C., Story of a VBAC rupture. 

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200. Combs, C.A., E.L. Murphy, and R.K. 

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201. Committee on Obstetric, P., 

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203. Coniglio, C. and J.E. Dickinson, 

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204. Coonrod, D.V., R.C. Bay, and G.Y. 

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205. Coulter, C.H. and R. Lehrfeld, When 

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206. Crane, J.M., et al., Maternal 

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207. Crane, S.S., et al., Association 

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208. Crawford, P. and L. Kaufmann, How 

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209. Cunha, M., et al., Induction of labor 

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210. Curtin, S.C., L.J. Kozak, and K.D. 

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211. Daltveit, A.K., et al., Cesarean 

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212. Dandolu, V., et al., Resident 

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213. Danforth, D.N., Cesarean section. 

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214. Daponte, A., et al., The use of 

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F-17 
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215. Daponte, A., et al., Pregnancy 

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216. Dashow, E.E., J.A. Read, and F.H. 

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217. Daskalakis, G.J., et al., Misoprostol 

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218. Dauphinee, J.D., VBAC: safety for 

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219. Davey, M.R., J. Moodley, and G.J. 

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220. David, M., et al., Prior cesarean 

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222. Davies, G.A., P.M. Hahn, and M.M. 

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223. Daviss, B.A., Vaginal delivery after 

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225. de Jong, P., Trial of labor following 

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226. de Muylder, X. and M. Thiery, The 

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227. de Regt, R.H., et al., Relation of 

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228. Declercq, E., M. Barger, and J.P. 

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230. Delaney, T. and D.C. Young, Trial 

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231. Delpapa, E.H. and E. MuellerHeubach, Pregnancy outcome 

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232. Demianczuk, N.N., D.J. Hunter, and 

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233. Deneux-Tharaux, C., et al., 

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234. Deutchman, M. and R.G. Roberts, 

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235. Diani, F., Fetal macrosomia and 

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237. Dildy, G.A., et al., Very advanced 

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239. DiMaio, H., et al., Vaginal birth 

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F-19 
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241. Dodd, J. and C. Crowther, Vaginal 

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243. Dodd, J., E. Pearce, and C. 

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245. Dodd, J.M. and C.A. Crowther, 

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259. Eltabbakh, G.H. and J.D. Watson, 

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280. Flamm, B.L., Vaginal birth after 

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286. Flamm, B.L., et al., External 

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292. Franz, M.B., et al., Stillbirth 

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293. Fraser, W., Women's mid-pregnancy 

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294. Frederiksen, M.C., R. Glassenberg, 

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295. French, L., Trial of labor after 

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303. Garg, V.K. and E.N. Ekuma-Nkama, 

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304. Gates, P.E., Think globally, act 

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305. Gellman, E., et al., Vaginal delivery 

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306. Gerhardstein, L.P., et al., Reduction 

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308. Gibbs, C.E., Planned vaginal 

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309. Gibbs, C.P., et al., Obstetric 

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311. Gil, A. and C.J. Sultana, 

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313. Gleicher, N., Mandatory trial of 

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314. Gochnour, G., S. Ratcliffe, and M.B. 

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315. Goer, H., Misoprostol and uterine 

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316. Goer, H., VBAC and the New 

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317. Goffman, D., et al., Predictors of 

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318. Goldman, G., et al., Effects of 

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319. Gonzales, G.F. and A. Salirrosas, 

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320. Gorgen, H., et al., Fetal torticollis 

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321. Goyert, G.L., et al., The physician 

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322. Graham, A.R., Trial labor following 

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323. Granot, M., Postcesarean section 

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324. Gray, R., et al., Caesarean delivery 

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325. Gregory, K.D., Maternal and infant 

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326. Gregory, K.D., et al., Repeat 

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328. Gross, T., R.J. Sokol, and K.C. King, 

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329. Gross, T.L., et al., Avoiding 

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330. Groutz, A., et al., Persistent 

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331. Grunebaum, A.N., et al., The 

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332. Gudgeon, C.W., Uterine rupture and 

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333. Guleria, K., G.I. Dhall, and K. Dhall, 

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334. Gupta, A., et al., Meconium stained 

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335. Haas, A.V., Homebirth after 

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336. Habek, D. and R. Becarevic, 

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337. Haberman, S., et al., Variations in 

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338. Hales, K., Influence of labor and 

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339. Hall, M.H., Mode of delivery and 

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340. Hamar, B.D., et al., Expectant 

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341. Hammond, H., Death from 

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343. Hankins, G.D.V., S.M. Clark, and 

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344. Haq, C.L., Vaginal birth after 

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345. Harper, L.M. and G.A. Macones, 

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349. Hawe, J.A. and K.S. Olah, Posterior 

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350. Hawkins, J.L., Obstetric anesthesia 

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351. Hawkins, J.L., et al., Oral intake 

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F-28 
Appendix F. Excluded Studies List, continued 

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353. Hawkins, J.L., et al., Anesthesiarelated deaths during obstetric 

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354. Heddleston, L.N. and W.J. Watson, 

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355. Heffner, L.J., Uterine rupture among 

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356. Hendricks, M.S., et al., Previous 

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359. Heritage, C.K. and M.D. 

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360. Hicks, P., Systematic review of the 

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361. Hildingsson, I., et al., Few women 

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362. Hill, D.A., et al., Uterine rupture and 

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363. Hodgkinson, R., Repeat caesarean 

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364. Hodnett, E.D., et al., Continuous 

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365. Hoffman, M.K., et al., Uterine 

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366. Hofmeyr, G.J., et al., Methods for 

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367. Hofmeyr, G.J. and A.M. 

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368. Hofmeyr, G.J. and M.E. Hannah, 

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369. Hofmeyr, G.J. and R. Kulier, 

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370. Hofmeyr, G.J., L. Say, and A.M. 

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371. Horey, D., J. Weaver, and H. 

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372. Howarth, G.R. and D.J. Botha, 

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373. Hsu, C.D., et al., Rupture of uterine 

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374. Hurry, D.J., B. Larsen, and D. 

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375. Hutton, E. and E. Mozurkewich, 

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376. Hutton, E.K. and G.J. Hofmeyr, 

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377. Iglesias, S., R. Burn, and L.D. 

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378. Imberti, R., et al., Blood transfusion 

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379. Imoh-Ita, F. and S. Williams, 

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380. Jackson, N. and S. Paterson-Brown, 

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381. Jacob, J. and J. Pfenninger, Cesarean 

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382. Jaillard, S., V. Houfflin-Debarge, 

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383. Janke, J.R., Breastfeeding duration 

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384. Janni, W., et al., The prognostic 

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385. Janssen, P.A., et al., Outcomes of 

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386. Jarrell, M.A., G.G. Ashmead, and 

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387. Jastrow, N., et al., Inter- and 

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388. Jerbi, M., et al., Predictive factors of 

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389. Jerbi, M., et al., Previous cesarean 

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390. Johnson, C. and N. Oriol, The role of 

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392. Johnson, S.R., et al., Obstetric 

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393. Jolly, M.C., Risk factors for 

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394. Jonas, H.A., N. Khalid, and S.M. 

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395. Jonas, H.A. and J.M. Lumley, The 

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396. Jones, R.O., et al., Rupture of low 

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397. Joseph, G.F., Jr., C.M. Stedman, and 

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398. Joura, E.A., Minimal wound closure 

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399. Joyce, D.N., F. Giwa-Osagie, and 

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400. Kabir, A.A., et al., Unnecessary 

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401. Kaczmarczyk, M., et al., Risk factors 

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402. Kamal, P., et al., Factors influencing 

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403. Kaplan, B., et al., Routine revision of 

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405. Karaer, A., F.A. Avsar, and S. 

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406. Kastner, E.S., et al., Emergency 

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407. Kavak, Z.N., A. Basgul, and N. 

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408. Kavanagh, J., A.J. Kelly, and J. 

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409. Kavanagh, J., A.J. Kelly, and J. 

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410. Kavanagh, J., A.J. Kelly, and J. 

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411. Kavanagh, J., A.J. Kelly, and J. 

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412. Kayani, S.I. and Z. Alfirevic, 

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414. Kelly, A., et al., Induction of labour 

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415. Kelly, A.J. and J. Kavanagh, Nitric 

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416. Kelly, A.J., J. Kavanagh, and J. 

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417. Kelly, A.J., J. Kavanagh, and J. 

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418. Kelly, A.J., J. Kavanagh, and J. 

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419. Kelly, A.J. and B. Tan, Intravenous 

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420. Kendrick, J.S., et al., Previous 

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421. Khan, K.S. and A. Rizvi, The 

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422. Khan, K.S., A. Rizvi, and J.H. Rizvi, 

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423. Kirk, E.P., et al., Vaginal birth after 

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424. Kirkinen, P., Multiple caesarean 

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425. Kirkinen, P., Ultrasonography of the 

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426. Kishor, T., et al., Study of vaginal 

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427. Kline, J. and F. Arias, Analysis of 

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F-34 
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429. Kobelin, C.G., Intrapartum 

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430. Kolas, T., et al., Indications for 

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431. Kolderup, L.B., R.K. Laros, Jr., and 

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432. Kopelman, J.N., et al., Computed 

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433. Koroukian, S.M., Uterine rupture 

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434. Koroukian, S.M., D. Bush, and A.A. 

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435. Koroukian, S.M. and A.A. Rimm, 

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436. Koroukian, S.M., B. Trisel, and A.A. 

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437. Korst, L.M., et al., Hospital rates of 

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438. Kotagal, U.R., et al., The impact of 

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439. Kozak, L.J. and J.D. Weeks, U.S. 

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440. Krishnamurthy, S., et al., The role of 

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441. Kuczkowski, K.M., Vaginal birth 

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442. Kwee, A., et al., Uterine rupture and 

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444. Lagrew, D.C., Jr. and J.A. Adashek, 

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445. Lam, C.M., S.F. Wong, and L.Y. 

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446. Landon, M.B., Vaginal birth after 

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447. Langer, O., Shoulder dystocia: 

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448. Lao, T.T. and B.F. Leung, Rupture of 

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449. Laopaiboon, M., et al., Music during 

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450. Laros, R.K., Jr., T.A. Flanagan, and 

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451. Latendresse, G., P.A. Murphy, and 

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452. Latthe, P., et al., Factors 

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F-36 
Appendix F. Excluded Studies List, continued 

453. Lavin, J.P., et al., Vaginal delivery in 

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454. Leaphart, W.L., M.C. Meyer, and 

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455. Lee, K.S., et al., Relationship of 

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456. Leeman, L. and R. Leeman, A Native 

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458. Lieberman, E., Risk factors for 

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459. Lieberman, E., et al., Assessing the 

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460. Linton, A. and M.R. Peterson, Effect 

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461. Linton, A., M.R. Peterson, and T.V. 

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F-37 
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466. Lomas, J., et al., Opinion leaders vs 

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467. Longo, D.R., et al., Consumer 

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469. Lurie, S., et al., Routine previous 

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470. Lyerly, A.D., et al., Risks, values, 

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471. Lynch, J.C. and J.P. Pardy, Uterine 

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472. Macario, A., Y.Y. El-Sayed, and 

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475. MacKenzie, I.Z., S. Bradley, and 

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476. Macones, G.A., The utility of clinical 

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F-38 
Appendix F. Excluded Studies List, continued 

478. Mahmood, T.A., Maternal height, 

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479. Mahmood, T.A., The influence of 

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480. Mahony, R., et al., Outcome of 

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481. Makino, S., et al., Prospective 

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482. Makoha, F.W., et al., Multiple 

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483. Mankuta, D.D., et al., Vaginal birth 

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484. Many, A., et al., Neonatal 

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485. Martel, M.-J., et al., Guidelines for 

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486. Martel, M.-J., et al., Guidelines for 

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487. Martin, J.N., Jr., J.C. Morrison, and 

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488. Martin, J.N., Jr., et al., The case for 

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489. Martin, L.F., K.M. Finigan, and T.E. 

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490. Maslow, A.S. and A.L. Sweeny, 

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F-39 
Appendix F. Excluded Studies List, continued 

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491. Mastrobattista, J.M., Vaginal birth 

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492. Matalon, S., et al., Relationship of 

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493. Mathelier, A.C., Radiopelvimetry 

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494. Mauldin, J.G. and R.B. Newman, 

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495. Mawson, A.R., Reducing cesarean 

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496. Maymon, E., et al., Peripartum 

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497. McCarthy, F.P., A. Ades, and W.C. 

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498. McClain, C.S., Why women choose 

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499. McClain, C.S., Patient decision 

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500. McClain, C.S., The making of a 

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501. McCracken, L., Issue 57: Cesarean 

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502. McDonagh, M.S., P. Osterweil, and 

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503. McShane, P.M., P.S. Heyl, and M.F. 

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F-40 
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505. Meehan, F.P., Delivery following 

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506. Meehan, F.P., Trial of scar with 

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507. Meehan, F.P., et al., Delivery 

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508. Meehan, F.P., G. Burke, and J.T. 

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509. Meehan, F.P., et al., True 

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510. Meehan, F.P. and I.M. Magani, True 

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511. Megafu, U., Factors influencing 

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512. Mehta, S.H., et al., Shoulder dystocia 

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F-41 
Appendix F. Excluded Studies List, continued 

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520. Miller, D.A., et al., Vaginal birth 

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521. Miller, E.S., J. Partezana, and R.L. 

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522. Miller, P.J., et al., The relationship 

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523. Milsom, I., et al., Influence of 

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524. Minkoff, H. and S. McCalla, Uterine 

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525. Minkoff, H.L., et al., The 

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F-42 
Appendix F. Excluded Studies List, continued 

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531. Mootabar, H., et al., Vaginal delivery 

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532. Moran, C., et al., Gastrin levels in 

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535. Morin, K.H. and L. Reilly, Caring 

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536. Morrison, J., Neonatal respiratory 

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537. Mor-Yosef, S., A. Samueloff, and 

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538. Mor-Yosef, S., et al., Vaginal 

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F-43 
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543. Murphy, D.J., et al., The relationship 

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544. Murphy, H., Uterine rupture without 

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545. Murphy, M.C. and S.M. Harvey, 

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546. Murray, T.M., Case 9-1998: uterine 

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547. Murta, E.F.C. and R.S. Nomelini, Is 

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548. Murtha, A.P., et al., Umbilical 

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549. Murthy, K., et al., Association 

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551. Myers, S.A. and N. Gleicher, A 

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552. Myles, T., Vaginal birth of twins 

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554. Nather, A., et al., Nonclosure of 

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555. Naulty, J.S., et al., Epidural fentanyl 

F-44 
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556. Ngu, A. and M.A. Quinn, Vaginal 

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557. Ni, H.Y., et al., Previous abdominal 

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558. Nicoll, A.E., et al., An audit of 

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559. Nielsen, T.F., H. Hagberg, and U. 

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560. Nielsen, T.F. and K.H. Hokegard, 

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561. Nielsen, T.F., U. Ljungblad, and H. 

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562. Nordin, A.J. and J.A. Richardson, 

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563. Norman, P., S. Kostovcik, and A. 

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564. Norris, M.C., Are combined spinal 

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565. November, M.T., Cost analysis of 

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566. Nuthalapaty, F.S., D.J. Rouse, and J. 

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567. Nwokoro, C.A., et al., Vaginal birth 

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571. Ofir, K., et al., Uterine rupture: risk 

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573. Ojo, V.A. and J.Y. Aliyu, 

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577. Oleske, D.M., et al., Cesarean and 

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578. Olive, E.C., et al., Placenta praevia: 

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579. Ollendorff, D.A., et al., Vaginal birth 

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580. Onwude, J.L., S. Rao, and D.O. 

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F-46 
Appendix F. Excluded Studies List, continued 

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584. O'Sullivan, M.J., et al., Vaginal 

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585. Oyelese, Y. and J.C. Smulian, 

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586. Ozdemir, I., N. Yucel, and O. Yucel, 

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587. Pan, P., Multifactorial preoperative 

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588. Parazzini, F., et al., Risk factors for 

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589. Parilla, B.V., et al., Iatrogenic 

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591. Penso, C., Vaginal birth after 

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592. Perez-Rios, N., G. Ramos-Valencia, 

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595. Peschers, U., et al., Changes in 

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F-47 
Appendix F. Excluded Studies List, continued 

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598. Petrikovsky, B.M., Endoscopic 

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599. Peyrat, L., et al., Prevalence and risk 

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603. Pinette, M.G., et al., Vaginal birth 

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604. Piver, M.S. and R.A. Johnston, Sr., 

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605. Placek, P.J., S. Taffel, and M. 

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606. Placek, P.J. and S.M. Taffel, The 

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611. Pollio, F., et al., Uterine dehiscence 

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616. Ponkey, S.E., et al., Persistent fetal 

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620. Pridjian, G., Labor after prior 

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638. Roberts, H., et al., Ectopic 

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662. Sanchez-Ramos, L., et al., Route of 

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665. Saunders, L.D. and G. Flowerdew, 

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666. Schimmel, L.M., et al., The Yolo 

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671. Sciscione, A.C., et al., A randomized 

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672. Scott, J.R., Mandatory trial of labor 

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675. Segal, S., et al., Evaluation of breast 

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678. Seow, K.M., et al., Cesarean scar 

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680. Shalev, E., et al., External cephalic 

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683. Sheiner, E., et al., Failed vacuum 

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686. Shin, Y.K., Shoulder pain in a trial 

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691. Shukunami, K.-I., K. Nishijima, and 

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695. Simon, R. and D. Altman, Statistical 

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696. Singh, P.M., C. Rodrigues, and A.N. 

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704. Songane, F.F., et al., Balancing the 

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705. Spaulding, L.B. and D.G. Gallup, 

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706. Spellacy, W.N., et al., Neonatal 

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707. Spetz, J., M.W. Smith, and S.F. 

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708. Spurrett, B. and C.M. Cook, Why we 

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709. Stafford, R.S., The impact of 

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710. Stalnaker, B.L., et al., 

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711. Stevenson, D.K., et al., Increased 

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712. Stone, J.L., et al., Use of cervical 

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713. Strong, T.H., Jr., et al., Vaginal birth 

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714. Stubbs, T.M., Oxytocin for labor 

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715. Sumigama, S., et al., Placenta previa 

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717. Sur, S., K.W. Murphy, and I.Z. 

Mackenzie, Delivery after caesarean 

section: consultant obstetricians' 

professional advice and personal 

preferences. J Obstet Gynaecol, 

2009. 29(3): p. 212-6. 

Exclusion code: 6 

718. Swaim, L.S., C.S. Holste, and D.K. 

Waller, Umbilical cord blood pH 

after prior cesarean delivery. Obstet 

Gynecol, 1998. 92(3): p. 390-3. 

Exclusion code: 5 

719. Szczesny, W., et al., Bishop score 

and the outcome of labor induction 

with misoprostol. Acta Obstet 

Gynecol Scand, 2006. 85(5): p. 579-

82. 

Exclusion code: 5 

720. Takayama, T., Risks associated with 

cesarean section in women with 

placenta previa. J Obstet Gynaecol 

Res, 1997. 23: p. 375-9. 

Exclusion code: 10 

721. Tammelleo, A.D., Failure to "fully 

communicate": catastrophic results. 

Case in point: Baptist Medical 

Center v. Wilson 618 So. 2d 1335--

AL (1993). Regan Rep Nurs Law, 

1993. 34(3): p. 2. 

Exclusion code: 9 

722. Tan, P.C., R.N. Subramaniam, and 

S.Z. Omar, Predictors for caesarean 

delivery and neonatal admission 

after trial of labour in women with 

one previous lower segment 

caesarean scar. Singapore Med J, 

2008. 49(3): p. 188-92. 

Exclusion code: 8 

723. Tan, P.C., R.N. Subramaniam, and 

S.Z. Omar, Trial of labor after one 

cesarean: role of the order and 

number of prior vaginal births on the 

risk of emergency cesarean delivery 

and neonatal admission. Taiwan, 

2008. 47(3): p. 305-11. 

Exclusion code: 5 

724. Targett, C., Caesarean section and 

F-57 
Appendix F. Excluded Studies List, continued 

trial of scar. Aust N Z J Obstet 

Gynaecol, 1988. 28(4): p. 249-62. 

Exclusion code: 10 

725. Tatar, M., et al., Women's 

perceptions of caesarean section: 

reflections from a Turkish teaching 

hospital. Soc Sci Med, 2000. 50(9): 

p. 1227-33. 

Exclusion code: 6 

726. Taylor, V.M., et al., Placenta previa 

and prior cesarean delivery: how 

strong is the association? Obstet 

Gynecol, 1994. 84(1): p. 55-7. 

Exclusion code: 5 

727. To, W.W. and W.C. Leung, Placenta 

previa and previous cesarean 

section. Int J Gynaecol Obstet, 1995. 

51(1): p. 25-31. 

Exclusion code: 7 

728. Tripathi, J.B., H.U. Doshi, and P.J. 

Kotdawala, Vaginal birth after one 

caesarean section: analysis of 

indicators of success. J Indian Med 

Assoc, 2006. 104(3): p. 113-5. 

Exclusion code: 8 

729. Tuggy, M.L., Uterine-vesicular 

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Board Fam Pract, 1995. 8(5): p. 405-

9. 

Exclusion code: 9 

730. Tuncer, R., et al., Emergency 

postpartum hysterectomy. J Gynecol 

Surg, 1995. 11(4): p. 209-13. 

Exclusion code: 5 

731. Turner, M.J., Delivery after one 

previous cesarean section. Am J 

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741-4. 

Exclusion code: 7 

732. Turner, M.J., Uterine rupture. Best 

Pract Res Clin Obstet Gynaecol, 

2002. 16(1): p. 69-79. 

Exclusion code: 6 

733. Turner, M.J.A., G. Agnew, and H. 

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Exclusion code: 4 

734. Turner, M.J.A., G. Agnew, and H. 

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after a previous low transverse 

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113(6): p. 729-32. 

Exclusion code: 11 

735. Turnquest, M.A., et al., Vaginal birth 

after cesarean section in a university 

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92(6): p. 216-21. 

Exclusion code: 4 

736. Tutschek, B., H.G. Bender, and W. 

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during vaginal delivery successfully 

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Obstet Gynecol, 2005. 26(2): p. 199-

200. 

Exclusion code: 9 

737. Udayasankar, V., R. Padmagirison, 

and F. Majoko, National survey of 

obstetricians in Wales regarding 

induction of labour in women with a 

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Exclusion code: 6 

738. Udo-Inyang, A., C. Lee, and E. 

F-58 
Appendix F. Excluded Studies List, continued 

Evans, Gravid uterine rupture 

following cesarean section and 

intervening vaginal delivery. Henry 

Ford Hosp Med J, 1986. 34(3): p. 

215-7. 

Exclusion code: 9 

739. Uppington, J., Epidural analgesia 

and previous Caesarean section. 

Anaesthesia, 1983. 38(4): p. 336-41. 

Exclusion code: 9 

740. Usta, I.M., et al., Placenta previaaccreta: risk factors and 

complications. Am J Obstet Gynecol, 

2005. 193(3 Pt 2): p. 1045-9. 

Exclusion code: 4 

741. Usta, I.M. and A.H. Nassar, 

Advanced maternal age. Part I: 

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Exclusion code: 5 

742. van Amerongen, D., Vaginal birth 

after cesarean section in an HMO. 

Hmo Pract, 1989. 3(3): p. 104-7. 

Exclusion code: 4 

743. van Amerongen, D., Vaginal birth 

after cesarean section. Experience in 

a community-based practice. J 

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Exclusion code: 4 

744. Van Bogaert, L.J., The relation 

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82(2): p. 195-9. 

Exclusion code: 7 

745. van Bogaert, L.J., Mode of delivery 

after one cesarean section. Int J 

Gynaecol Obstet, 2004. 87(1): p. 9-

13. 

Exclusion code: 4 

746. van Loon, A.J., et al., Randomised 

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presentation at term. Lancet, 1997. 

350(9094): p. 1799-804. 

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747. van Roosmalen, J. and C.D. van der 

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1995. 47(1): p. 19-22. 

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748. Varner, M.W., et al., The MaternalFetal Medicine Unit cesarean 

registry: trial of labor with a twin 

gestation. Am J Obstet Gynecol, 

2005. 193(1): p. 135-40. 

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749. Varner, M.W., et al., Trial of labor 

after one previous cesarean delivery 

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750. Vause, S. and M. Macintosh, 

Evidence based case report: use of 

prostaglandins to induce labour in 

women with a caesarean section 

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8. 

Exclusion code: 9 

751. Veille, J.C., et al., Human umbilical 

artery flow velocity waveforms 

before and after regional anesthesia 

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F-59 
Appendix F. Excluded Studies List, continued 

Exclusion code: 4 

752. Vellekoop, J., E.A.M. Roell-Schorer, 

and J. van Roosmalen, Uterine scar 

rupture after a previous cesarean 

section and induction of labor with 

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Exclusion code: 9 

753. Veltman, L., Vaginal birth after 

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754. Vendittelli, F., et al., Is a breech 

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755. Vengadasalam, D., Vaginal delivery 

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Singapore Med J, 1986. 27(5): p. 

396-8. 

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756. Veridiano, N.P., N.S. Thorner, and J. 

Ducey, Vaginal delivery after 

cesarean section. Int J Gynaecol 

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Exclusion code: 5 

757. Wadhawan, S. and J.N. Narone, 

Outcome of labor following previous 

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758. Wagner, M., What every midwife 

should know about ACOG and 

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Exclusion code: 6 

759. Wallace, D.H., et al., Indirect 

sonographic guidance for epidural 

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patients. Reg Anesth, 1992. 17(4): p. 

233-6. 

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760. Wareham, V., C. Bain, and D. 

Cruickshank, Caesarean section 

audit by peer review. Eur J Obstet 

Gynecol Reprod Biol, 1993. 48(1): p. 

9-14. 

Exclusion code: 4 

761. Warren, L., A revelation in birth--

home VBAC. Midwifery Today Int 

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762. Wax, J.R., et al., Pregnancy 

following gastric bypass surgery for 

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763. Wax, J.R., et al., Twin vaginal birth 

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64(4): p. 205-8. 

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764. Wax, J.R., et al., Interpregnancy 

interval as a risk factor for placenta 

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659-61. 

Exclusion code: 5 

F-60 
Appendix F. Excluded Studies List, continued 

765. Weeks, A., et al., Misoprostol for 

induction of labor with a live fetus. 

Int J Gynaecol Obstet, 2007. 99 

Suppl 2: p. S194-7. 

Exclusion code: 6 

766. Weeks, J.W., T. Pitman, and J.A. 

Spinnato, 2nd, Fetal macrosomia: 

does antenatal prediction affect 

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Am J Obstet Gynecol, 1995. 173(4): 

p. 1215-9. 

Exclusion code: 5 

767. Weiss, J., A. Nannini, and L. 

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women with a prior cesarean 

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346(2): p. 134-7. 

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768. Whiteman, M.K., et al., Incidence 

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108(6): p. 1486-92. 

Exclusion code: 4 

769. Whiteside, D.C., C.S. Mahan, and 

J.C. Cook, Factors associated with 

successful vaginal delivery after 

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1983. 28(11): p. 785-8. 

Exclusion code: 7 

770. Wilson, P.D., R.M. Herbison, and 

G.P. Herbison, Obstetric practice 

and the prevalence of urinary 

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1996. 103(2): p. 154-61. 

Exclusion code: 5 

771. Windrim, R., Vaginal delivery in 

birth centre after previous caesarean 

section. Lancet, 2005. 365(9454): p. 

106-7. 

Exclusion code: 6 

772. Wing, D.A. and C.A.L. Gaffaney, 

Vaginal misoprostol administration 

for cervical ripening and labor 

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2006. 49(3): p. 627-41. 

Exclusion code: 4 

773. Wing, D.A. and R.H. Paul, Vaginal 

birth after cesarean section: 

selection and management. Clin 

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48. 

Exclusion code: 6 

774. Wood, S.L., et al., The risk of 

unexplained antepartum stillbirth in 

second pregnancies following 

caesarean section in the first 

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Exclusion code: 7 

775. Woods, J.R., Jr., et al., The effect of 

labor on maternal and fetal vitamins 

C and E. Am J Obstet Gynecol, 

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Exclusion code: 5 

776. Yamani, T.Y. and A.A. Rouzi, 

Induction of labor with vaginal 

prostaglandin-E2 in grand 

multiparous women with one 

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251-3. 

Exclusion code: 8 

777. Yamani Zamzami, T.Y., Indication 

of emergency peripartum 

hysterectomy: review of 17 cases. 

F-61 
Appendix F. Excluded Studies List, continued 

Arch Gynecol Obstet, 2003. 268(3): 

p. 131-5. 

Exclusion code: 8 

778. Yamani Zamzami, T.Y., Vaginal 

birth after cesarean section in grand 

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Exclusion code: 8 

779. Yamani-Zamzami, T.Y., Delivery 

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28(12): p. 1845-9. 

Exclusion code: 8 

780. Yang, J.I., et al., Sonographic 

findings of placental lacunae and the 

prediction of adherent placenta in 

women with placenta previa totalis 

and prior Cesarean section. 

Ultrasound Obstet Gynecol, 2006. 

28(2): p. 178-82. 

Exclusion code: 4 

781. Yang, Y.T., et al., Relationship 

between malpractice litigation 

pressure and rates of cesarean 

section and vaginal birth after 

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782. Yangzom, Y., et al., Outcome of 

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p. 317-21. 

Exclusion code: 8 

783. Yap, O.W., E.S. Kim, and R.K. 

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labor. Am J Obstet Gynecol, 2001. 

184(7): p. 1576-81. 

Exclusion code: 10 

784. Yasumizu, T., et al., Trial of vaginal 

birth following cesarean section for 

arrest disorders of labor: analysis of 

patients with well-documented 

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Obstet Gynaecol, 1994. 20(4): p. 

407-13. 

Exclusion code: 7 

785. Yeh, S., X. Huang, and J.P. Phelan, 

Postterm pregnancy after previous 

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1984. 29(1): p. 41-4. 

Exclusion code: 10 

786. Yogev, Y., et al., Induction of labor 

with vaginal prostaglandin E2. J 

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14(1): p. 30-4. 

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787. Yu, C.K.H., T.G. Teoh, and S. 

Robinson, Obesity in pregnancy. 

Bjog, 2006. 113(10): p. 1117-25. 

Exclusion code: 6 

788. Yudkin, P.L. and C.W. Redman, 

Caesarean section dissected, 1978-

1983. Br J Obstet Gynaecol, 1986. 

93(2): p. 135-44. 

Exclusion code: 7 

789. Zagorzycki, M.T. and C.R. 

Brinkman, 3rd, The effect of general 

and epidural anesthesia upon 

neonatal Apgar scores in repeat 

cesarean section. Surg Gynecol 

Obstet, 1982. 155(5): p. 641-5. 

Exclusion code: 7 

790. Zaideh, S.M., A.T. Abu-Heija, and 

F-62 
Appendix F. Excluded Studies List, continued 

M.F. El-Jallad, Placenta praevia and 

accreta: analysis of a two-year 

experience. Gynecol Obstet Invest, 

1998. 46(2): p. 96-8. 

Exclusion code: 8 

791. Zaki, Z.M., et al., Risk factors and 

morbidity in patients with placenta 

previa accreta compared to placenta 

previa non-accreta. Acta Obstet 

Gynecol Scand, 1998. 77(4): p. 391-

4. 

Exclusion code: 8 

792. Zhang, J. and D.A. Savitz, Maternal 

age and placenta previa: a 

population-based, case-control 

study. Am J Obstet Gynecol, 1993. 

168(2): p. 641-5. 

Exclusion code: 4 

793. Zhuang, Y.L., et al., [Treatment of 

pregnancy in a previous caesarean 

section scar with uterine artery 

embolization: analysis of 60 cases]. 

Zhonghua yi xue za zhi, 2008. 

88(33): p. 2372-4. 

Exclusion code: 8 

794. Ziadeh, S.M. and A.T. Abu-Heija, 

Duration of labor in patients 

delivered vaginally after one 

previous lower segment cesarean 

section. Int J Gynaecol Obstet, 1994. 

45(3): p. 213-5. 

Exclusion code: 8 

795. Ziadeh, S.M., M.R. Zakaria, and E.I. 

Sunna, Obstetric uterine rupture in 

north Jordan. J Obstet Gynaecol 

Res, 1996. 22(3): p. 209-13. 

Exclusion code: 8 

796. Zorlu, C.G., et al., Vaginal birth 

following unmonitored labor in 

patients with prior cesarean section. 

Gynecol Obstet Invest, 1996. 42(4): 

p. 222-6. 

Exclusion code: 4 

797. Zweifler, J., et al., Vaginal birth 

after cesarean in California: before 

and after a change in guidelines. 

Ann Fam Med, 2006. 4(3): p. 228-

34. 

Exclusion code: 7 

F-63 
Appendix F. Excluded Studies List, continued 

Studies excluded by specific topics of interest: 

Trial of labor and vaginal birth after cesarean rates: 

Studies were excluded from the trial of labor and vaginal birth after cesarean rates sections for 

various reasons, these include: limited population that was not comparable to others included, 

poor quality studies, examined the same group of cohort as included studies, studies were not 

specific about all who was eligible for a trial of labor. 

1. Blanchette, H., et al., Is vaginal birth 6. Gibson, D.H., Vaginal delivery after 

after cesarean safe? Experience at a 

community hospital. Am J Obstet 

Gynecol, 2001. 184(7): p. 1478-84; 

caesarean section in primigravidae. 

Ir J Med Sci, 1988. 157(9): p. 290-2. 

discussion 1484-7. 7. Gonen, R., et al., Variables 

2. Bujold, E., et al., Modified Bishop's 

associated with successful vaginal 

birth after one cesarean section: a 

score and induction of labor in 

patients with a previous cesarean 

delivery. Am J Obstet Gynecol, 

2004. 191(5): p. 1644-8. 

proposed vaginal birth after 

cesarean section score. Am J 

Perinatol, 2004. 21(8): p. 447-53. 

8. Grobman, W.A., et al., Pregnancy 

3. Cahill, A.G., et al., Is vaginal birth outcomes for women with placenta 

after cesarean (VBAC) or elective 

repeat cesarean safer in women with 

a prior vaginal delivery? Am J 

Obstet Gynecol, 2006. 195(4): p. 

previa in relation to the number of 

prior cesarean deliveries. Obstet 

Gynecol, 2007. 110(6): p. 1249-55. 

1143-7. 9. Heddleston, L.N. and W.J. Watson, 

4. Carroll, C.S., Sr., et al., Vaginal birth 

after cesarean section versus elective 

Vaginal birth after cesarean section 

in a small hospital. Mil Med, 1991. 

156(5): p. 239-40. 

repeat cesarean delivery: Weightbased outcomes. Am J Obstet 10. Kabir, A.A., et al., Racial differences 

Gynecol, 2003. 188(6): p. 1516-20; in cesareans: an analysis of U.S. 

discussion 1520-2. 2001 National Inpatient Sample 

5. Chauhan, S.P., et al., Mode of 

delivery for the morbidly obese with 

prior cesarean delivery: vaginal 

versus repeat cesarean section. Am J 

Obstet Gynecol, 2001. 185(2): p. 11. 

Data.[see comment][erratum 

appears in Obstet Gynecol. 2005 

Jun;105(6):1495]. Obstet Gynecol, 

2005. 105(4): p. 710-8. 

King, D.E. and K. Lahiri, 

349-54. Socioeconomic factors and the odds 

of vaginal birth after cesarean 

delivery. Jama, 1994. 272(7): p. 524-

9. 

F-64 
Appendix F. Excluded Studies List, continued 

12. Landon, M.B., et al., Maternal and 

perinatal outcomes associated with a 

trial of labor after prior cesarean 

delivery. N Engl J Med, 2004. 

351(25): p. 2581-9. 

13. Leung, A.S., E.K. Leung, and R.H. 

Paul, Uterine rupture after previous 

cesarean delivery: maternal and 

fetal consequences. Am J Obstet 

Gynecol, 1993. 169(4): p. 945-50. 

14. Melnikow, J., et al., Vaginal birth 

after cesarean in California. Obstet 

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15. Mercer, B.M., et al., Labor outcomes 

with increasing number of prior 

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111(2 Pt 1): p. 285-91. 

16. Montgomery, A.A., et al., Two 

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among women with previous 

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334(7607): p. 1305. 

17. Paterson, C.M. and N.J. Saunders, 

Mode of delivery after one caesarean 

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303(6806): p. 818-21. 

18. Paul, R.H., J.P. Phelan, and S.Y. 

Yeh, Trial of labor in the patient 

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Obstet Gynecol, 1985. 151(3): p. 

297-304. 

19. Peaceman, A.M., et al., The MFMU 

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size on trial of labor success for 

patients with previous cesarean for 

dystocia. Am J Obstet Gynecol, 

2006. 195(4): p. 1127-31. 

20. Quinones, J.N., et al., The effect of 

prematurity on vaginal birth after 

cesarean delivery: success and 

maternal morbidity. Obstet Gynecol, 

2005. 105(3): p. 519-24. 

21. Rudick, V., et al., Epidural analgesia 

for planned vaginal delivery 

following previous cesarean section. 

Obstet Gynecol, 1984. 64(5): p. 621-

3. 

22. Shorten, A., et al., Making choices 

for childbirth: a randomized 

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2005. 32(4): p. 252-61. 

23. Srinivas, S.K., et al., Predicting 

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24. Stone, C., et al., Vaginal births after 

Caesarean (VBAC): a population 

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2000. 14(4): p. 340-8. 

25. van der Walt, W.A., H.S. Cronje, 

and R.H. Bam, Vaginal delivery after 

one cesarean section. Int J Gynaecol 

Obstet, 1994. 46(3): p. 271-7. 

F-65 
Appendix F. Excluded Studies List, continued 

Uterine rupture 

Studies not using the anatomical definition, defined as: complete uterine rupture – separation 

through the entire thickness of the wall including visceral serosa (with or without extrusion of 

part of all of fetal-placental unit). The following studies were excluded from the risk of uterine 

rupture section of the report because they did not use this definition. 

1. Amir, W., J. Peter, and Z. Etan, Trial 

of labor without oxytocin in patients 

with a previous cesarean section. 

Am J Perinatol, 1987. 4(2): p. 140-3. 

8. Fisler, R.E., et al., Neonatal outcome 

after trial of labor compared with 

elective repeat cesarean section. 

Birth, 2003. 30(2): p. 83-8. 

2. Bais, J.M., et al., Vaginal birth after 

caesarean section in a population 9. Flamm, B.L., et al., Elective repeat 

with a low overall caesarean section cesarean delivery versus trial of 

rate. Eur J Obstet Gynecol Reprod 

Biol, 2001. 96(2): p. 158-62. 

labor: a prospective multicenter 

study. Obstet Gynecol, 1994. 83(6): 

p. 927-32. 

3. Blanchette, H., et al., Is vaginal birth 

after cesarean safe? Experience at a 10. Granovsky-Grisaru, S., M. Shaya, 

community hospital. Am J Obstet 

Gynecol, 2001. 184(7): p. 1478-84; 

and Y.Z. Diamant, The management 

of labor in women with more than 

discussion 1484-7. one uterine scar: is a repeat 

cesarean section really the only 

4. Bujold, E., S.C. Blackwell, and R.J. 

Gauthier, Cervical ripening with 

"safe" option? J Perinat Med, 1994. 

22(1): p. 13-7. 

transcervical foley catheter and the 

risk of uterine rupture. Obstet 

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11. Gregory, K.D., et al., Vaginal birth 

after cesarean: clinical risk factors 

associated with adverse outcome. 

5. Bujold, E., et al., The impact of a Am J Obstet Gynecol, 2008. 198(4): 

single-layer or double-layer closure p. 452.e1-10; discussion 452.e10-2. 

on uterine rupture. Am J Obstet 

Gynecol, 2002. 186(6): p. 1326-30. 12. Grossetti, E., et al., Rupture of the 

6. Eglinton, G.S., et al., Outcome of a 

scarred uterus. Acta Obstet Gynecol 

Scand, 2007. 86(5): p. 572-8. 

trial of labor after prior cesarean 

delivery. J Reprod Med, 1984. 29(1): 13. Grubb, D.K., S.L. Kjos, and R.H. 

p. 3-8. Paul, Latent labor with an unknown 

7. Eriksen, N.L. and L. Buttino, Jr., 

uterine scar. Obstet Gynecol, 1996. 

88(3): p. 351-5. 

Vaginal birth after cesarean: a 

comparison of maternal and 14. Hammoud, A., et al., The effect of 

neonatal morbidity to elective repeat gestational age on trial of labor after 

cesarean section. Am J Perinatol, Cesarean section. J Matern Fetal 

1989. 6(4): p. 375-9. Neonatal Med, 2004. 15(3): p. 202-6. 

F-66 
Appendix F. Excluded Studies List, continued 

15. Hibbard, J.U., et al., Failed vaginal 

birth after a cesarean section: how 

risky is it? I. Maternal morbidity. 

Am J Obstet Gynecol, 2001. 184(7): 

p. 1365-71; discussion 1371-3. 

16. Hollard, A.L., et al., Ethnic disparity 

in the success of vaginal birth after 

cesarean delivery. J Matern Fetal 

Neonatal Med, 2006. 19(8): p. 483-7. 

17. Hook, B., et al., Neonatal morbidity 

after elective repeat cesarean section 

and trial of labor. Pediatrics, 1997. 

100(3 Pt 1): p. 348-53. 

18. Juhasz, G., et al., Effect of body mass 

index and excessive weight gain on 

success of vaginal birth after 

cesarean delivery. Obstet Gynecol, 

2005. 106(4): p. 741-6. 

19. Lieberman, E., et al., Results of the 

national study of vaginal birth after 

cesarean in birth centers. Obstet 

Gynecol, 2004. 104(5 Pt 1): p. 933-

42. 

20. Lin, C. and B.D. Raynor, Risk of 

uterine rupture in labor induction of 

patients with prior cesarean section: 

an inner city hospital experience. 

Am J Obstet Gynecol, 2004. 190(5): 

p. 1476-8. 

21. Martin, J.N., Jr., et al., Vaginal 

delivery following previous cesarean 

birth. Am J Obstet Gynecol, 1983. 

146(3): p. 255-63. 

22. Meehan, F.P. and G. Burke, Trial of 

labour following prior section; a 5 

year prospective study (1982-1987). 

Eur J Obstet Gynecol Reprod Biol, 

1989. 31(2): p. 109-17. 

23. Meier, P.R. and R.P. Porreco, Trial 

of labor following cesarean section: 

a two-year experience. Am J Obstet 

Gynecol, 1982. 144(6): p. 671-8. 

24. Menihan, C.A., Uterine rupture in 

women attempting a vaginal birth 

following prior cesarean birth. J 

Perinatol, 1998. 18(6 Pt 1): p. 440-3. 

25. Nguyen, T.V., et al., Vaginal birth 

after cesarean section at the 

University of Texas. J Reprod Med, 

1992. 37(10): p. 880-2. 

26. Obara, H., et al., Vaginal birth after 

cesarean delivery: results in 310 

pregnancies. J Obstet Gynaecol Res, 

1998. 24(2): p. 129-34. 

27. Phelan, J.P., et al., Vaginal birth 

after cesarean. Am J Obstet 

Gynecol, 1987. 157(6): p. 1510-5. 

28. Quinones, J.N., et al., The effect of 

prematurity on vaginal birth after 

cesarean delivery: success and 

maternal morbidity. Obstet Gynecol, 

2005. 105(3): p. 519-24. 

29. Sakala, E.P., et al., Oxytocin use 

after previous cesarean: why a 

higher rate of failed labor trial? 

Obstet Gynecol, 1990. 75(3 Pt 1): p. 

356-9. 

30. Schneider, J., D. Gallego, and R. 

Benito, Trial of labor after an earlier 

cesarean section. A conservative 

approach. J Reprod Med, 1988. 

33(5): p. 453-6. 

F-67 
Appendix F. Excluded Studies List, continued 

31. Socol, M.L. and A.M. Peaceman, 

community with a solo practice. Am 

J Perinatol, 2003. 20(2): p. 63-7. 

32. 

Vaginal birth after cesarean: an 

appraisal of fetal risk. Obstet 

Gynecol, 1999. 93(5 Pt 1): p. 674-9. 

Stovall, T.G., et al., Trial of labor in 

35. van der Walt, W.A., H.S. Cronje, 

and R.H. Bam, Vaginal delivery after 

one cesarean section. Int J Gynaecol 

Obstet, 1994. 46(3): p. 271-7. 

previous cesarean section patients, 

excluding classical cesarean 

sections. Obstet Gynecol, 1987. 

70(5): p. 713-7. 

36. Wen, S.W., et al., Comparison of 

maternal mortality and morbidity 

between trial of labor and elective 

33. Tahilramaney, M.P., et al., Previous 

cesarean section and trial of labor. 

cesarean section among women with 

previous cesarean delivery. Am J 

Obstet Gynecol, 2004. 191(4): p. 

Factors related to uterine 1263-9. 

dehiscence. J Reprod Med, 1984. 

29(1): p. 17-21. 37. Zwart, J.J., et al., Uterine rupture in 

The Netherlands: a nationwide 

34. Upadhyaya, C.D., D.M. Upadhyaya, 

and S.J. Carlan, Vaginal birth after 

population-based cohort study. Bjog, 

2009. 116(8): p. 1069-78; discussion 

cesarean delivery in a small rural 1078-80. 

F-68 
 

Appendix G. List of Citations From the Maternal-Fetal 

Medicine Units Network Cohort 

Overview: This appendix contains the full-text papers used from the National Institute of 

Child Health and Human Development Maternal-Fetal Medicine Units Network 

(MFMU) in this report by key question. 

Description of overall cohort: The MFMU cohort drew subjects from 19 academic 

medical centers and report on 45,988 women with singleton gestation and prior cesarean 

delivery. The Network, established in 1986, was designed to focus on clinical questions 

in maternal-fetal medicine and obstetrics, particularly with respect to the continuing 

problem of preterm birth. 

Key Question 1 

• Grobman, 20071 

• Landon, 20042 

• Mercer, 20083 

• Peaceman, 20064 

Key Question 2 

• Grobman, 20075 

• Grobman, 20086 

• Hibbard, 20067 

• Landon, 20042 

• Landon, 20068 

• Mercer, 20083 

• Rouse, 20069 

• Silver, 200610 

• Spong, 200711 

Key Question 3 

• Grobman, 20075 

• Hibbard, 20067 

• Landon, 20068 

• Spong, 200711 

G-1 
Appendix G. List of Citations From the Maternal-Fetal 

Medicine Units Network Cohort, continued 

References 

1. Grobman WA, Lai Y, Landon 

MB, et al. Development of a 

nomogram for prediction of 

vaginal birth after cesarean 

delivery. Obstet Gynecol. 

2007;109(4):806-812. 

2. Landon MB, Hauth JC, Leveno 

KJ, et al. Maternal and perinatal 

outcomes associated with a trial 

of labor after prior cesarean 

delivery. N Engl J Med. 

2004;351(25):2581-2589. 

3. Mercer BM, Gilbert S, Landon 

MB, et al. Labor outcomes with 

increasing number of prior 

vaginal births after cesarean 

delivery. Obstet Gynecol. 

2008;111(2 Pt 1):285-291. 

4. Peaceman AM, Gersnoviez R, 

Landon MB, et al. The MFMU 

Cesarean Registry: impact of 

fetal size on trial of labor success 

for patients with previous 

cesarean for dystocia. American 

Journal of Obstetrics & 

Gynecology. 2006;195(4):1127-

1131. 

5. Grobman WA, Gilbert S, Landon 

MB, et al. Outcomes of induction 

of labor after one prior cesarean. 

Obstet Gynecol. 2007;109(2 Pt 

1):262-269. 

6. Grobman WA, Lai Y, Landon 

MB, et al. Prediction of uterine 

rupture associated with attempted 

vaginal birth after cesarean 

delivery. American Journal of 

Obstetrics & Gynecology. 

2008;199(1):30.e31-35. 

7. Hibbard JU, Gilbert S, Landon 

MB, et al. Trial of labor or repeat 

cesarean delivery in women with 

morbid obesity and previous 

cesarean delivery. Obstet 

Gynecol. 2006;108(1):125-133. 

8. Landon MB, Spong CY, Thom 

E, et al. Risk of uterine rupture 

with a trial of labor in women 

with multiple and single prior 

cesarean delivery. Obstet 

Gynecol. 2006;108(1):12-20. 

9. Rouse DJ, MacPherson C, 

Landon M, et al. Blood 

transfusion and cesarean 

delivery.[erratum appears in 

Obstet Gynecol. 2006 

Dec;108(6):1556]. Obstet 

Gynecol. 2006;108(4):891-897. 

10. Silver RM, Landon MB, Rouse 

DJ, et al. Maternal morbidity 

associated with multiple repeat 

cesarean deliveries. Obstet 

Gynecol. 2006;107(6):1226-

1232. 

11. Spong CY, Landon MB, Gilbert 

S, et al. Risk of uterine rupture 

and adverse perinatal outcome at 

term after cesarean delivery. 

Obstet Gynecol. 

2007;110(4):801-807. 

G-2 
Appendix H. Quality Rating Criteria 

Introduction 

Quality assessment of individual studies is a critical and necessary step in conducting an 

evidence review. Quality assessment is an assessment of a study’s internal validity (the study’s 

ability to measure what it intends to measure). If a study is not conducted properly, the results 

that they produce are unlikely to represent the truth and thus are worthless (the old adage garbage 

in garbage out). If however, a study is structurally and analytically sound, then the results are 

valuable. A systematic review, is intended to evaluate the entire literature and distill those studies 

which are of the highest possible quality and therefore likely to be sound and defensible to affect 

practice. 

Our senior advisory team reviewed the literature around quality assessment including: 

We were searching for a system that was able to evaluate the entire breadth of study 

designs as the Obstetric literature and vaginal birth after cesarean literature spans all study types. 

Using one system that is able to cover all study designs, makes it easier for the reader to 

understand quality assessments across study designed that are included in any given topic. For 

example, the topic of uterine rupture will include randomized controlled trials of induction of 

labor or other interventions but will also necessarily include cohort, case series, and case control 

literature. 

We concluded that the quality assessment tool that was used in the last report remained 

the optimal choice for this current review. We felt that this was likely to be widely applicable 

across clinical reviews, and as such, we have developed a user’s guide to the quality assessment 

tool to increase reliability across staff. 

H-1 
Appendix H. Quality Rating Criteria, continued 

Taxonomy of study designs1 

Experimental designs 

A study in which the investigator has control over at least some study conditions, particularly 

decisions concerning the allocation of participants to different intervention groups. 

Randomized controlled trial 

Participants are randomly allocated to intervention or control groups and flowed up over time 

to assess any differences in outcome rates. Randomization with allocation concealment 

ensures that on average known and unknown determinants of outcome are evenly distributed 

between groups. 

Observational designs 

A study in which natural variation in interventions (or exposure) among study participants is 

investigated to explore the effect of the interventions (or exposure) on health outcomes. 

Cohort study 

A follow-up study that compares outcomes between participants who have received an 

intervention and those who have not. Participants are studied during the same (concurrent) 

period either prospectively or, more commonly, retrospectively. 

Case-control study 

Participants with and without a given outcome are identified (cases and controls respectively) 

and exposure to a given intervention(s) between the two groups compared. 

Cross-sectional study 

Examination of the relationship between disease and other variables of interest as they exist 

in a defined population at one particular time point. 

Case series 

Description of a number of cases of an intervention and outcome (no comparison with a 

control group). 

H-2 
Appendix H. Quality Rating Criteria, continued 

Hierarchy of Study Designs 

H-3
 
Appendix H. Quality Rating Criteria, continued 

Randomized Controlled Trials Table Example 

Quality Criteria Study, Year Random assignment Allocation concealed 

Groups comparable at 

baseline & maintained 

What should First author, Y/N/Unclear Y/N/Unclear Y/N/Unclear 

be in the cell Year of 

Publication Yes Yes Yes 

Definitions -computer-generated 

random numbers -random numbers tables No -use of alternation -case record numbers -birth dates -days of the week -horoscope Unclear reports study as randomized, but provides no details on approach or not reported 

-centralized or pharmacycontrolled serially-numbered identical containers -on-site computer based system with a randomization sequence that is not readable until allocation No -open random numbers lists -serially numbered envelopes (even sealed opaque envelopes can be subject to manipulation) Unclear not reported or reports study as concealed, but provides no details on approach 

-comparison groups are balanced for relevant baseline characteristics, either describin the text or in a table -comparable groups were maintained throughout the stuNo (if no, state reason) -there are noted differences between the groups at baselin-authors excluded a group of people after they were randomized Unclear does not state that groups wedifferent, but does not provide data to allow reader to compagroups on baseline characteristics 

H-4 
Appendix H. Quality Rating Criteria, continued 

Randomized Controlled Trials Table Example, continued 

Blinded: Outcome Assessors/ 

Care Provider/Patient 

Report of attrition 

Differential loss to follow-up Analysis considerati

Y/N/Unclear Please note: answer for each person; outcome assessors, care providers and patients Yes -Blinding is used to keep the participants, investigators and outcome assessors ignorant about the interventions which participants are receiving during a study. Blinding of outcome assessment can often be done even when blinding of participants and caregivers cannot. Blinding is used to protect against performance bias and detection bias. It may also contribute to adequate allocation concealment. No -open label -un-blinded Unclear reports as 'blind' or 'double blind' but no details are provided 

Attrition rate=% Differential loss to follow-up=% Report the actual attrition rate, per group - < 20% - Good - < 40% - Fair Calculate the differential loss to follow-up 

Y/N/Unclear Yes -ITT analysis is followed, not only but actually followed in the result-included all who were randomizeanalysis -<5% missing data without includthe analysis No -specifically exclude people from -conduct ONLY a per protocol anUnclear reports ITT, but provides no detaanalysis 

H-5 
Appendix H. Quality Rating Criteria, continued 

Randomized Controlled Trials Descriptors 

Random assignment – The process by which study participants are allocated to treatment 

groups in a trial. Adequate (that is, unbiased) methods of randomization include computer 

generated schedules and random-numbers tables. 

Allocation concealed – The process by which the person determining eligibility, consent, and 

enrollment is unaware of which group the next patient is to be assigned. 

Groups comparable at baseline & maintained - The researchers need to explicitly describe 

their groups at baseline and how they may or may not differ on important prognostic factors. 

These types of comparable groups must be maintained throughout the study as well. This 

becomes very important and can be tricky to assess. We know that some women who end up 

with a cesarean will have opted for a trial of labor and some who opted for a cesarean prior to 

trial of labor will go into labor. Thus issues such as inclusion from intended cohort and intention 

to treat analyses are important. 

Eligibility criteria specified – The researchers need to be explicit in laying out the eligibility 

criteria. This will include what inclusion criteria needed to be met to be eligible for the study as 

well as the reasons why they excluded particular individuals. This information is important to 

determine generalizability of the study. 

Blinded: Outcome Assessors/Care Provider/Patient – A way of making sure that the people 

involved in a research study — participants, clinicians, or researchers —do not know which 

participants are assigned to each study group. Blinding usually is used in research studies that 

compare two or more types of treatment for an illness. Blinding is used to keep the participants, 

investigators and outcome assessors ignorant about the interventions which participants are 

receiving during a study. Blinding of outcome assessment can often be done even when blinding 

of participants and caregivers cannot. Blinding is used to protect against performance bias and 

detection bias. It may also contribute to adequate allocation concealment. 

Report of attrition/Differential loss to follow-up – For every study, some proportion of 

participants is likely to dropout or be lost to follow-up due to a number of reasons. Loss to 

follow-up occurs when there is a loss of contact with some participants, so that researchers 

cannot complete data collection as planned, and do not know why the participants discontinued. 

Loss to follow-up is a common cause of missing data, especially in long-term studies. An 

acceptable attrition rate is < 20% for a good quality rating and < 40% for a fair quality rating. 

Analysis considerations – The use of data from a randomized controlled trial in which data 

from all randomized patients are accounted for in the final results. Trials often incorrectly report 

results as being based on intention to treat despite the fact that some patients are excluded from 

the analysis. If co-interventions occurred the researchers need to describe how these were 

handled in the analysis. 

H-6 
Appendix H. Quality Rating Criteria, continued 

Cohort Studies Table Example 

Quality 

Criteria 

Study, Year/ 

Design Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures reliable & 

valid 

What should First author, Y/N/Unclear Y/N/Unclear Y/N/Unclear be in the cell Year of 

Publication This is analogous to ITT. Yes 

Definitions Study design 

as determined by investigator 

Yes -authors layout explicit eligibility criteria in the methods section -authors reference another article for methods and we are able to pull the information from that article No -authors imply eligibility criteria, but do not explicitly state it 

Yes -comparison groups are balanced for relevant baseline characteristics, either described in the text or in a table -relevant, important prognostic factors are similar across groups -comparable groups are maintained throughout the study No (if no, state reason) -there are noted differences between the groups at baseline Unclear does not state that groups were different, but does not provide data to allow reader to compare groups on baseline characteristics 

-validated, standard measurement used No -study uses questions they came up with, but have not validated or standardized Unclear There is mention of a measure used, but it is not described 

H-7 
Appendix H. Quality Rating Criteria, continued 

Cohort Studies Table Example, continued 

Missing data 

Follow-up long 

enough for 

outcomes to occur 

Consider/adjust for potential 

confounders (obstetric 

conditions) 

Clear definition o

prognostic factors

Overall differential loss to follow-up=% Report the actual attrition rate, per group - < 20% - Good - < 40% - Fair Calculate the differential loss to follow-up 

Y/N/Unclear Has enough time passed to allow measured outcomes to occur? 

Y/N/Unclear/NA Consider Yes -descriptions of potential confounders are noted -the authors describe confounders that they are aware of in the groups No no mention of potential confounders Adjust Yes statistical analysis conducted to minimize the affect of potential confounders No no statistical analysis is mentioned 

Y/N/Unclear 

H-8 
Appendix H. Quality Rating Criteria, continued 

Cohort Studies Descriptors 

Assembly of groups– In a cohort study, the assembly and maintenance of comparable groups is 

critical. Sometimes you will hear people talking about inception cohort that is the vision of a 

group of patients who represent the target population. In most intervention studies, you would 

want the intervention group to be as similar to the placebo group as possible with the only 

exception being the intervention. If this is sound, then whatever differences you measure 

between intervention and non intervention should be based upon the intervention itself. This 

issue can be difficult in obstetrics, particularly relating to delivery as the intervention in that, 

patients often self select to groups and there may be systematic reasons why people would 

choose different options which may also contribute to outcomes. Nonetheless, our goal in a 

systematic review is to ask were the groups assembled for cesarean versus trial of labor similar to 

each other. That is, would the group that had the cesarean have been eligible for a trial of labor in 

the first place? If the group who had a cesarean all had placenta previas, this population would 

not be eligible for a trial of labor and there are ways in which the group with placenta previa 

would be expected to differ in outcomes regardless of choice of intervention. The first test 

should be to examine the populations, look at whatever groups were systematically removed 

from the cohort assembled, and ensure that what remains in the TOL and Cesarean group are 

otherwise comparable. 

Maintenance of comparable groups – This also becomes very important and can be tricky to 

assess. We know that some women who end up with a cesarean will have opted for a trial of 

labor and some who opted for a cesarean prior to trial of labor will go into labor. This topic is 

analogous to intention to treat analysis. The ideal cohort study would keep the patients in their 

original groups e.g. trial of labor versus repeat cesarean and report outcomes based upon that 

“inception cohort.” Doing this allows the study to report on outcomes for real experience that 

include adverse effects. It may be easier to understand the importance of this by looking at what 

happens if you don’t follow this. A VBAC study takes all women who intend trial of labor at 35 

weeks and then reports on repeat cesarean without labor as the cesarean comparator and places 

the patients instead into the trial of labor groups reasoning that this group underwent labor. The 

outcome profile for the cesarean group is likely to be unrealistically positive in that labor 

increases the opportunity for infection, fetal intolerance of labor etc. Similarly, what a clinician 

can tell a patient is only what their experience would be if they chose cesarean and never went 

into labor rather than what the patient and clinician would like to know, what are the chance that 

I might go into labor anyways before my scheduled cesarean and what would be the implications 

for that. This maintenance must be maintained through analysis. 

Outcome measures reliable and valid – Were the researchers clear and specific about the 

outcome measures? They should have identified the outcome they were attempting to identify, 

and then identify the measure(s) they were using to capture that outcome. This may for example, 

be ICD-9 codes in a study using a database that includes these codes. In this case, the researchers 

should identify how they determined the validity and reliability of these codes for the outcome 

measure of interest. If the outcomes were clinical measures abstracted from patient charts, the 

determination of an outcome should be well defined, and there should be indication that some 

assessment of the validity and reliability of decisions made by those making the determinations. 

H-9 
Appendix H. Quality Rating Criteria, continued 

In the best studies, the researchers will discuss why they selected specific outcome measures, for 

example, why they selected the HAM-D scale rather than the MADRS scale to measure 

depression, what change on the scale indicated clinically meaningful improvement or response, 

and so on. 

Outcome assessors blind to exposure status – Were the outcome assessors blinded to which 

group the patient belonged? Those making determinations of whether an outcome occurred or 

not should ideally be unaware of which group that patient was in. This can be achieved in most 

cases. When the outcomes are being assessed retrospectively, the researcher recording outcome 

measure should be looking only at outcome data, separated from intervention data. If this is truly 

not possible, for example, the outcome data are described in such a way that the group the patient 

is in is apparent, then researchers who are not aware of the study purpose at the time of 

abstracting the outcome measure data can be employed. Blinding of outcome measure 

assessment is important even when it seems like the determination of the outcome is black and 

white. Many outcome assessments are in fact subjective, because the data are not perfect such 

that judgments have to be made along the way. While identifying mortality may be quite clear in 

most cases, there are situations where the data may be less reliable. More difficult is identifying 

the cause of death, if that is an outcome measure. 

Missing data – For every study, some proportion of participants is likely to dropout or be lost to 

follow-up due to a number of reasons. Loss to follow-up occurs when there is a loss of contact 

with some participants, so that researchers cannot complete data collection as planned, and do 

not know why the participants discontinued. Loss to follow-up is a common cause of missing 

data, especially in long-term studies. An acceptable attrition rate is < 20% for a good quality 

rating and < 40% for a fair quality rating. 

Follow-up long enough for outcomes to occur – Was the follow-up period long enough? The 

researchers should indicate that they have thought through the disease process in detail when 

designing their study, such that the period of follow-up is long enough to allow the outcome to 

occur. If the outcome is mortality associated with hepatitis C, then a follow-up period of only 

several weeks is likely to be inadequate. If the researchers have not indicated reasoning for their 

selection of follow-up period, then you need to consider this determination. 

Consider/adjust for potential important confounders – A confounder is a characteristic of 

study subjects that is a common cause of the exposure and the outcome. Researchers need to 

identify what potential confounders are possible given their study and when possible adjust for 

these confounders using statistical analysis. 

Clear definition of prognostic factors* – In addition to these quality criteria, the evaluation of 

prediction modeling studies required that they provided a clear definitions of prognostic factors 

(1 extra criterion). The most important criteria for these studies were: comparable groups that 

included clear inclusion and exclusion criteria; clear definitions of the prognostic factors; 

adjustment (as needed, for studies without comparable groups) for confounders. To achieve a 

good rating, minimally, the study had to meet these three ratings. A study with comparable 

groups and no need for adjustment could still meet this standard. For studies that only met 2 of 

these 3 criteria, the highest rating they could achieve was fair. 

H-10 
Appendix H. Quality Rating Criteria, continued 

*For prediction modeling studies only. 

H-11
 
Appendix H. Quality Rating Criteria, continued 

Case-Control Studies Table Example 

Quality 

Criteria 

Author, 

Year 

Explicit definition 

of cases 

Disease state of the cases 

similar & reliably assessed 

Case ascertainment 

reliable, valid & applied 

appropriately 

N

What should be in the cell Definitions 

First author, Year of Publication 

Y/N Authors must clearly state how they defined who is considered a case. 

Y/N/Unclear Cases should be similar in respect to time course of disease; this may include capturing all cases along a spectrum or focus on cases at a similar point in their progression of the disease/condition. 

Y/N/Unclear Y

YCa

H-12 
Appendix H. Quality Rating Criteria, continued 

Case-Control Studies Table Example, continued 

Cases/controls: comparable 

confounding factors 

Study procedures applied 

equally 

Appropriate attention to 

confounders (consider & adjust) 

Appropriate stat

analysis used (ma

unmatched, overm

Y/N/Unclear Were they matched on important factors (i.e., age, SES, # of prior C/S, etc)? 

Y/N/Unclear Are the procedures & measurement of exposure accurate & applied equally? 

Y/N/Unclear/NA Consider Yes -descriptions of potential confounders are noted -the authors describe confounders that they are aware of in the groups No no mention of potential confounders Adjust Yes statistical analysis conducted to minimize the affect of potential confounders No no statistical analysis is mentioned 

Y/N/Unclear 

H-13 
Appendix H. Quality Rating Criteria, continued 

Case-Control Studies Descriptors 

Explicit definition of cases – It is important to ensure that the authors clearly state how they 

defined who would be considered a case and that these cases are determined by outcome (e.g. 

cancer). A case definition may not be a definitive health outcome but rather an intermediate 

outcome such as in the case of uterine rupture for obstetric research. 

Disease state of the cases similar and reliably assessed – When there is a spectrum of disease 

such as in the case of cancer or neurologic injury of a fetus, considerations of whether the cases 

are similar to one another in relation to time course of disease is important to consider. 

Depending on the stated objective, you may wish to capture all cases along the spectrum or to 

focus such that cases are at a similar point in their progression of disease. 

Case ascertainment reliable, valid and applied appropriately – How did the authors assess 

whether the patient was a case, how reliable is this method, and how did they ascertain cases? 

For example in the case of leukemia research use of ICD-9 codes, not clearly stated, histological 

evaluation by 2 pathologists, excluded all adopted children (this may be important if you were 

evaluating the effect of exposure to radiation and this was geographically represented rather than 

biologically inherited). In the obstetric literature, case control studies have been conducted on 

cases of uterine rupture. Studies have used ICD-9 codes to ascertain cases, however there are 

several that may apply. Some of the codes are more specific to uterine rupture while others 

include not only uterine rupture but also surgical extension of uterine incisions, which is not a 

uterine rupture. Studies that include the latter would have a consistent mechanism to apply but 

research has shown that the latter code is unreliable to ascertain cases. The next question once 

you know what method people use to identify cases is where they apply them. For example, 

hospitals’ discharge summaries in a single institution, identification from a cancer registry, 

governmental databases, laboratory pathological diagnoses. Similar to the conceptual cohort idea 

of the cohort study this is where you are asking whether the methods are likely to capture all 

cases that would be of interest. 

Nonbiased selection of controls – The issue of ensuring that controls are comparable to cases is 

critical to the quality and reliability of a case control study. Selecting a noncomparable control 

may skew the results and make then uninterruptable. 

Cases/controls: comparable confounding factors – The cases and controls should be 

comparable with respect to potential confounding factors. Otherwise, the results must be 

interpreted with this bias in mind. 

Study procedures applied equally - Are the procedures & measurement of exposure accurate & 

applied equally? All measurements should be applied to both cases and controls equally and 

accurately. 

Appropriate attention to confounders (consider & adjust) - A confounder is a characteristic 

of study subjects that is a risk factor (determinant) for the outcome to the putative cause, or is 

associated (in a statistical sense) with exposure to the putative cause. Researchers need to 

H-14 
Appendix H. Quality Rating Criteria, continued 

identify what potential confounders are possible given their study and when possible adjust for 

these confounders using statistical analysis. 

Appropriate statistical analysis used (matched, unmatched, overmatching) – Was the 

method used for statistical analysis appropriate? Did the researchers match their controls and 

cases appropriately? Beware of overmatching by researchers as well, when they match the 

subjects on too many variables making the results uninterruptable as well. 

H-15 
Appendix H. Quality Rating Criteria, continued 

Case Series Studies Table Example 

Sufficient Follow-up long 

Representative sample description of enough for 

Quality Author, selected from a Explicit definition of distribution of important events 

Criteria Year relevant population cases prognostic factors to occur 

What should First Y/N/Unclear Y/N Y/N/Unclear/NA Y/N/Unclear 

be in the cell author, 

Year of Is the population Yes Did the authors 

Definitions Publication examined relevant to the -authors layout allow enough time 

disease and age group? or atypical? 

explicit definitions for their cases 

for the outcomes to occur. 

Yes -randomly selected from 

-authors reference another article for 

registry methods and we are -consecutive patients No -self-selected volunteers 

able to pull the information from that article 

-investigator selected No 

-authors imply definition, but do not explicitly state it 

H-16 
Appendix H. Quality Rating Criteria, continued 

Case Series Studies Descriptors 

Representative sample selected from a relevant population – For case series studies, 

the cases being selected must be representative of the overall population. This will 

require the judgment of experts in the particular subject matter being studied to 

understand if the cases represent the broader population they are being drawn from. The 

researchers need to describe the overall population and how their cases are a 

representative sample of this overall population. 

Explicit definition of cases – It is important to ensure that the authors clearly state how 

they defined who will be considered a case and that these cases are determined by 

outcome (e.g. cancer). A case definition may not be a definitive health outcome but rather 

an intermediate outcome such as in the case of uterine rupture for obstetric research. 

Sufficient description of distribution of prognostic factors – A prognostic factor is a 

situation or condition, or a characteristic of a patient, that can be used to estimate the 

chance of recovery from a disease or the chance of the disease recurring. The researchers 

should explicitly describe the prognostic factors that are relevant to the group(s). 

Follow-up long enough for important outcomes to occur – Was the follow-up period 

long enough? The researchers should indicate that they have thought through the disease 

process in detail when designing their study, such that the period of follow-up is long 

enough to allow the outcome to occur. If the outcome is success of a trial of labor in a 

pregnant woman with a previous cesarean delivery, then a follow-up period of only 

several hours is adequate. However, if the outcome is neurological sequelae in the infant, 

then a much longer period of follow-up is necessary, possibly years are required. If the 

researchers have not indicated reasoning for their selection of follow-up period, then you 

will need to consider this determination. 

Outcomes assessed using objective criteria/blinding used – Were the outcome 

assessors blinded to which group the patient belonged? Those making determinations of 

whether an outcome occurred or not should ideally be unaware of which group that 

patient was in. This can be achieved in most cases. When the outcomes are being 

assessed retrospectively, the researcher recording outcome measure should be looking 

only at outcome data, separated from intervention data. If this is truly not possible, for 

example, the outcome data are described in such a way that the group the patient is in is 

apparent, then researches who are not aware of the study purpose at the time of 

abstracting the outcome measure data can be employed. Blinding of outcome measure 

assessment is important even when it seems like the determination of the outcome is 

black and white. Many outcome assessments are in fact subjective, because the data are 

not perfect such that judgments have to be made along the way. While identifying 

mortality may be quite clear in most cases, there are situations where the data may be less 

reliable. More difficult is identifying the cause of death, if that is an outcome measure. 

H-17 
Appendix H. Quality Rating Criteria, continued 

Rating Determinations2 

Good (low risk of bias). These studies have the least bias and results are considered 

valid. A study that adheres mostly to the commonly held concepts of high quality 

including the following: a formal randomized controlled study; clear description of the 

population, setting, interventions, and comparison groups; appropriate measurement of 

outcomes; appropriate statistical and analytic methods and reporting; no reporting errors; 

low dropout rate; and clear reporting of dropouts. 

Fair. These studies are susceptible to some bias, but it is not sufficient to invalidate the 

results. They do not meet all the criteria required for a rating of good quality because they 

have some deficiencies, but no flaw is likely to cause major bias. The study may be 

missing information, making it difficult to assess limitations and potential problems. 

Poor (high risk of bias). These studies have significant flaws that imply biases of 

various types that may invalidate the results. They have serious errors in design, analysis, 

or reporting; large amounts of missing information; or discrepancies in reporting. 

H-18 
Appendix H. Quality Rating Criteria, continued 

References 

1. Adapted from: Deeks JJ, Dinnes J, D'Amico R, et al. Evaluating non-randomised 

intervention studies. Health Technology Assessment. 2003;7(27):iii-x, 1-173. 

2. Agency for Healthcare Research and Quality. Methods Reference Guide for 

Effectiveness and Comparative Effectiveness Reviews, Version 1.0. Rockville, 

MD 2007. 

H-19 
Appendix I. Quality Ratings of Randomized Controlled Tria

Study, Year 

Random 

assignment 

Allocation 

concealed 

Groups 

comparable 

at baseline 

& 

maintained 

Eligibility 

criteria 

specified 

Blinded: 

Outcome 

Assessors/ 

Care Provider/ 

Patient 

Report of 

attrition 

Differential 

loss to followup Analy

consider

Grubb, 19961 Yes No Yes Yes No/No/No 8/188 lost to 

follow-up, 

<20% 

Ye

Peleg, 19992 Yes Yes NR Yes No/No/No Unclear Uncle

Thubisi, 19933 

No. 

"Allocated 

alternately by 

admitting 

clerks" 

No Yes Yes No/No/No No data given No 

Wing, 19984 NR NR NR/NR Yes No/No/No No data given No 

I-1 
Appendix I. Quality Ratings of Cohort Studies
 

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

e

Amir, 19875 Yes Yes Unclear 

Asakura, 19956 Unclear Unclear Unclear 

Bahtiyar, 20067 Yes Yes No 

Bais, 20018 Yes Unclear Yes 

Bashiri, 20089 Yes No Yes 

Blanchette, 199910 

Yes Unclear Unclear 

Blanchette, 200111 

Unclear No No 

Bujold, 200212 Yes No Unclear 

Bujold, 200213 Yes Yes Yes 

Bujold, 200414 Yes Yes Unclear 

I-2 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Amir, 19875 None Yes Yes/No 

Asakura, 19956 Unclear Yes No/No 

Bahtiyar, 20067 Unclear Yes Yes/Yes 

Bais, 20018 No Yes Yes/No 

Bashiri, 20089 No Yes Yes/Yes 

Blanchette, 199910 Not reported Yes No/No 

Blanchette, 200111 

Unclear Yes Yes/Yes for uterine rupture, 

no for all others 

Bujold, 200212 Unclear Yes Yes/Yes 

Bujold, 200213 No Yes Yes/Yes 

Bujold, 200414 No Yes Yes/Yes 

I-3 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outcom

e

Bujold, 200415 Yes Yes Unclear 

Bujold, 200516 Yes Yes Yes 

Cahill, 200617 Yes No Yes 

Carroll, 200318 Yes Unclear Unclear 

Caughey, 199919 Yes Yes Unclear 

Chang, 200820 

Yes Yes Yes 

Chapman, 199721 

Yes No Unclear 

Chauhan, 200122 

Yes No Yes 

Chauhan, 200223 

Yes Unclear Unclear 

I-4 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Bujold, 200415 No Yes Yes/Yes 

Bujold, 200516 No Yes Yes/Yes 

Cahill, 200617 No Yes Yes/Yes 

Carroll, 200318 Unclear Yes Yes/Yes 

Caughey, 199919 <20% Yes Yes/Yes 

Chang, 200820 

None Yes Yes/Yes 

Chapman, 199721 

Unclear Yes No/No 

Chauhan, 200122 

No Yes Yes/Some 

Chauhan, 200223 

Low, 1/156 Yes Yes/Yes 

I-5 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Chestnut, 198524 

Unclear Yes Unclear 

Coughlan, 200225 

Yes No Yes 

DeFranco, 200726 

Yes Yes Yes 

Delaney, 200327 Yes Yes Yes 

Dhall, 198728 Yes Unclear Unclear 

DiMaio, 200229 Yes No Yes 

Dinsmoor, 200430 

Yes No Yes 

Duff, 198831 Yes Unclear Yes 

Durnwald, 200432 

Unclear Unclear Yes 

I-6 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Chestnut, 198524 Maternal morbidity for postop: 25%; Other outcomes: 

0% for other outcomes 

Yes Some/No 

Coughlan, 200225 

Unclear Yes No/No 

DeFranco, 200726 

None Yes Yes/Yes 

Delaney, 200327 None Yes Yes/No 

Dhall, 198728 Not reported Yes Yes/Yes 

DiMaio, 200229 Not applicable Yes No 

Dinsmoor, 200430 

Low, 12% Yes Yes/Yes 

Duff, 198831 Unclear Yes No/No 

Durnwald, 200432 

Unclear Yes Yes/Yes 

I-7 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Durnwald, 200433 

Yes Yes No 

Edwards, 200334 

Yes Unclear No 

Eglinton, 198435 Yes Unclear Yes 

Elkousy, 200336 Unclear Unclear No 

El-Sayed, 200737 

Unclear Not applicable Unclear 

Eriksen, 198938 Unclear Yes Unclear 

Fisler, 200339 Yes Yes Yes 

Flamm, 198740 Yes Not applicable Yes 

Flamm, 198941 Yes Unclear Unclear 

I-8 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Durnwald, 200433 

No Yes No/No 

Edwards, 200334 No Yes Yes/No 

Eglinton, 198435 Low, 5% Yes Yes/Yes 

Elkousy, 200336 Unclear Yes Yes/Yes 

El-Sayed, 200737 

<20% Yes Yes/Yes 

Eriksen, 198938 No Yes Some/No 

Fisler, 200339 No Yes Yes/Yes 

Flamm, 198740 Not applicable Yes Yes/Yes 

Flamm, 198941 No Unclear No/No 

I-9 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Flamm, 199442 Yes Not applicable Yes 

Flamm, 199743 Yes Yes Yes Gemer, 199244 Yes Unclear Yes 

Getahun, 200645 Unclear Unclear Unclear 

Gibson, 198846 Unclear Unclear Unclear 

Gonen, 200647 Unclear No Yes 

Gonen, 200748 Yes No Unclear 

Goodall, 200549 Yes Unclear Yes 

GranovskyGrisaru, 199450 Yes Unclear Unclear 

I-10 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Flamm, 199442 Not applicable Yes Yes/Yes 

Flamm, 199743 Not applicable Yes Yes/Yes Gemer, 199244 No Yes Yes/No Getahun, 200645 Unclear Yes Yes/Yes 

Gibson, 198846 None Yes No/No 

Gonen, 200647 Unclear Yes Yes/Yes 

Gonen, 200748 Unclear Yes No/No 

Goodall, 200549 No Yes Yes/Yes 

GranovskyGrisaru, 199450 Not applicable Yes Yes/Yes 

I-11 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Gregory, 199951 Yes Not applicable Yes 

Gregory, 200852 Yes No No 

Grobman, 200753 

Yes Unclear Yes 

Grobman, 200854 

Yes Unclear Yes 

Grossetti, 200755 Unclear Yes Unclear 

Hammoud, 200456 

Yes No Unclear 

Hansell, 199057 Yes Yes Yes 

Hashima, 200758 Yes No Yes 

Hemminki, 200559 

Yes Unclear Unclear 

I-12 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Gregory, 199951 Not applicable Not applicable Yes/Yes 

Gregory, 200852 Unclear Unclear Yes/Yes 

Grobman, 

200753 

No Yes Yes/Yes 

Grobman, 

200854 Missing 30% of body mass indexes, and 25% of prior 

birth weights 

Yes Yes/Yes 

Grossetti, 200755 No Yes Unclear 

Hammoud, 

200456 

Unclear Yes Yes/Yes 

Hansell, 199057 No Yes Yes/No 

Hashima, 200758 Unclear Yes Yes/Yes 

Hemminki, 

200559 

1.20% Yes Yes/Yes 

I-13 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Hershkowitz, 199560 

Yes Unclear Unclear 

Hibbard, 200161 Unclear No Yes 

Hibbard, 200662 Yes Yes Yes 

Hollard, 200663 Yes No Yes 

Hook, 199764 Yes Yes Yes 

Horenstein, 198465 

Unclear Yes Unclear 

Horenstein, 198566 

Unclear Yes Unclear 

Hoskins, 199767 Yes Not applicable Yes 

Johnson, 199168 Yes Unclear Yes 

I-14 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Hershkowitz, 199560 

Unclear Yes Yes/Yes 

Hibbard, 200161 ERCD: 2.4%; VBAC: 6.9% Yes Yes/Yes 

Hibbard, 200662 No Yes Yes/Yes 

Hollard, 200663 No Yes Yes/Yes 

Hook, 199764 No Yes Yes/Yes 

Horenstein, 198465 

No Yes Very little/No 

Horenstein, 198566 

No Yes Very little/No 

Hoskins, 199767 Not applicable Yes No 

Johnson, 199168 Unclear Yes No/No 

I-15 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Juhasz, 200569 Yes Unclear Yes 

Kamath, 200970 Yes No Yes 

Kayani, 200571 Yes Yes Unclear 

Kugler, 200872 Unclear Not applicable No 

Kwee, 200773 Yes Unclear Yes 

Landon, 200474 Yes No Yes 

Landon, 200675 Yes No Yes 

Lieberman, 200476 Yes Yes Unclear 

Lin, 200477 Yes Yes Yes 

I-16 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough for 

outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Juhasz, 200569 No Yes Yes/Yes 

Kamath, 200970 No Yes Yes/Yes 

Kayani, 200571 No Yes Very little/No 

Kugler, 200872 No Yes No/No 

Kwee, 200773 No Yes No/No 

Landon, 200474 < 20% Yes Yes/Yes 

Landon, 200675 <20% - 7% (unknown intent 

to trial of labor) 

Yes Yes/Yes 

Lieberman, 200476 Unclear Yes Yes/No 

Lin, 200477 No Yes Unclear 

I-17 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Loebel, 200478 Unclear Yes Unclear 

Lydon-Rochelle, 200179 

Yes No Unclear 

Lyndon-Rochelle, 200180 

Yes Not applicable No 

Macones, 200581 Yes Not applicable Yes 

Martin,198382 Yes Not applicable Yes. No for fever 

McMahon, 199683 Yes Not applicable Yes 

Melnikow, 200184 Yes Unclear Yes 

Miller, 199285 Yes Not applicable Yes 

Naef, 199586 Yes No Yes 

I-18 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough 

for outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Loebel, 200478 No Yes No/No 

Lydon-Rochelle, 200179 No data given Yes Yes/Yes 

Lyndon-Rochelle, 200180 Not applicable Yes Yes/Yes 

Macones, 200581 Not applicable Yes Yes/No 

Martin,198382 Not applicable Yes No/No 

McMahon, 199683 Not applicable Yes Yes/Yes 

Melnikow, 200184 Low, 73/1662 Not applicable Not reported 

Miller, 199285 Not applicable Not applicable No/No 

Naef, 199586 Unclear Yes No/No 

I-19 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Nisenblat, 200687 Yes No Yes 

Obara, 199888 Yes No Unclear 

Odibo, 200789 Yes Unclear unclear 

Ogunyemi, 199890 Yes No Unclear 

Ouzounian, 199691 Unclear Yes Yes 

Paterson, 199192 Yes Yes Unclear 

Pathadey, 200593 Yes Yes Unclear 

Paul, 198594 Yes Not applicable Yes 

Peaceman, 200695 Yes No Yes 

I-20 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough 

for outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Nisenblat, 200687 Unclear Yes Yes/Yes 

Obara, 199888 Unclear Yes Yes/No 

Odibo, 200789 Unclear Yes Yes/Yes 

Ogunyemi, 199890 No Yes No/No 

Ouzounian, 199691 No Yes No/No 

Paterson, 199192 Not applicable Yes Unclear 

Pathadey, 200593 No Yes Yes/No 

Paul, 198594 Not applicable Yes Yes/No 

Peaceman, 200695 Unclear Yes Yes/Yes 

I-21 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Phelan, 198796 Yes Not applicable Yes 

Phelan, 198997 Yes Unclear Yes for uterine rupture. No 

for fever 

Pruett, 198898 Yes Unclear Yes 

Quinones, 200599 Unclear Unclear Yes 

Rageth, 1999100 No Not applicable No 

Ravasia, 2000101 Unclear No No 

Raynor, 1993102 Yes Not applicable Yes 

Richardson, 2005103 

Yes Unclear Yes 

Richter, 2002104 Yes No Yes 

I-22 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough 

for outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Phelan, 198796 Not applicable Yes Yes/No 

Phelan, 198997 No Yes Yes/No 

Pruett, 198898 Unclear Yes No/No 

Quinones, 200599 low Yes Yes/Yes 

Rageth, 1999100 Not applicable Yes No/No 

Ravasia, 2000101 No Yes No/No 

Raynor, 1993102 Not applicable Yes No 

Richardson, 2005103 

No Yes Yes/Yes 

Richter, 2002104 No Yes Some/No 

I-23 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Rozenberg, 1996105 

Yes Yes Yes 

Rozenberg, 1999106 

No Yes Yes 

Rudick, 1984107 Yes Yes Unclear 

Russillo, 2008108 Yes Unclear Unclear 

Sakala, 1990109 Yes Yes Unclear 

Sakala, 1990110 Unclear Unclear Unclear 

Schneider, 1988111 Inclusion criteria are described, but 

methods to ascertain group are not discussed. Elective repeat cesarean group includes medical and obstetric reasons as well as maternal decisions, and methods for ascertaining the reason are not described 

Unclear Unclear 

Sciscione, 2008112 Yes No Yes 

Rozenberg, 1996105 

Yes Yes Yes 

I-24 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough 

for outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Rozenberg, 1996105 

No Yes Yes/Yes 

Rozenberg, 1999106 

No Yes Yes/Unclear 

Rudick, 1984107 No Yes Yes/No 

Russillo, 2008108 No Yes Yes/No 

Sakala, 1990109 No Yes Yes/No 

Sakala, 1990110 No Yes No/No 

Schneider, 1988111 No Yes Yes/No 

Sciscione, 2008112 No Yes Yes/Yes 

I-25 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Shipp, 2008113 Yes No Yes 

Smith, 2002114 Yes Yes Yes Socol, 1999115 Yes Unclear Yes 

Spaans, 2003116 Yes Unclear Unclear 

Spong, 2007117 Yes. However, the number 

(39,177) for term singleton gestation with prior cesarean is different from prior publication (Landon, 2006) 

Yes Yes 

Stone, 2000118 Unclear Not applicable Unclear 

Strong, 1992119 Unclear Yes No 

Stovall, 1987120 Yes Not applicable Yes/Yes 

Tahilramaney, 1984121 

Yes Yes Unclear 

I-26 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough 

for outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Shipp, 2008113 No Yes Yes/Yes 

Smith, 2002114 No Yes Yes/Some Socol, 1999115 No Yes No/No 

Spaans, 2003116 Unclear Yes No/No 

Spong, 2007117 Yes Yes Yes/Yes 

Stone, 2000118 Not applicable Yes No/No 

Strong, 1992119 No Yes No/No 

Stovall, 1987120 Not applicable Yes No 

Tahilramaney, 1984121 

No Yes Yes/Yes 

I-27 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Tucker, 1993122 Yes Unclear No 

Upadhyaya, 2003123 

Unclear Unclear Yes 

Van der Walt, 1994124 

Unclear Unclear Yes 

Van Gelderen, 1986125 

Unclear Yes Unclear 

Videla, 1995126 Yes Unclear No 

Weinstein, 1996127 Yes Yes For some, not for others 

Wen, 2004128 Unclear Yes Unclear 

Yetman, 1989129 Yes Unclear No 

Yogev, 2004130 Unclear Yes Yes 

I-28 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough 

for outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Tucker, 1993122 No Yes No/No 

Upadhyaya, 2003123 Not applicable Yes Yes/Yes 

Van der Walt, 1994124 

Yes Yes Yes/Yes 

Van Gelderen, 1986125 

No Yes No/No 

Videla, 1995126 Yes Yes No/No 

Weinstein, 1996127 Not applicable Yes Yes/Yes 

Wen, 2004128 No Yes Some/Some 

Yetman, 1989129 Low, 5% Yes No/No 

Yogev, 2004130 No Yes Yes/Yes 

I-29 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Assembly of Groups 

Maintenance of 

comparable groups 

Outcome measures 

reliable & valid 

Outco

Zelop, 1999131 Yes Yes Yes 

Zelop, 2000132 Yes Unclear No Zelop, 2001133 Yes Yes Yes 

I-30 
Appendix I. Quality Ratings of Cohort Studies, continued

Study, Year Missing data 

Follow-up long enough 

for outcomes to occur 

Consider/adjust for 

potential confounders 

(obstetric conditions) 

Zelop, 1999131 No Yes No/No 

Zelop, 2000132 Yes Yes No/No 

Zelop, 2001133 Not applicable Yes Yes/Yes 

I-31 
Appendix I. Quality Ratings of Case-Control Studies
 

Study, Year 

Explicit 

definition 

of cases 

Disease 

state of 

the cases 

similar & 

reliably 

assessed 

Case 

ascertainment 

reliable, valid 

& applied 

appropriately 

Nonbiased 

selection 

of controls 

Cases/controls: 

comparable 

confounding 

factors 

Study 

procedures 

applied 

equally 

Appro

attenti

confou

(consi

adju

Adair, 1995134 Yes Unclear Unclear No No Unclear Yes/

Bashiri, 20089 Yes Unclear No Yes No No Unc

Bodelon, 2009135 

Yes Yes Unclear Yes No Unclear Yes/

Buhimschi, 2005136 

Yes Yes Yes Yes Yes Yes No/

Gilliam, 2002137 Yes Yes No Yes No Yes Yes/

Guihard, 2001138 Yes Yes Yes Unclear Unclear Yes Yes/

Hadley, 1986139 Somewhat Yes Yes Yes No Yes NA 

Juntunen, 2004140 

Yes Unclear Yes Unclear Unclear Yes No/

I-32 
Appendix I. Quality Ratings of Case-Control Studies, continu

Study, Year 

Explicit 

definition 

of cases 

Disease 

state of 

the 

cases 

similar & 

reliably 

assessed 

Case 

ascertainment 

reliable, valid 

& applied 

appropriately 

Nonbiased 

selection 

of 

controls 

Cases/controls: 

comparable 

confounding 

factors 

Study 

procedures 

applied 

equally 

Appr

atten

confo

(cons

ad

Kacmar, 2003141 Yes Yes Unclear Yes No Yes Yes

Laughon, 2005142 Yes Yes Yes Yes No Yes Yes

Leung, 1993143 Yes Yes Unclear Yes Unclear Unclear No

Macones, 2001144 Yes Yes/No Yes No Yes Yes/No Yes

Macones, 200581 Yes Yes No Unclear Unclear Yes Yes/U

Macones, 2006145 Yes Yes Yes Yes No Yes Yes

McMahon, 1997146 

Yes Unclear. 

Used 

birth 

certificate 

data for 

previa 

Unclear Yes No Unclear No

Miles, 2000147 Yes Yes Unclear No Unclear Unclear Som

Pickhardt, 1992148 Yes Yes/No Yes/No No Yes Yes/No Y

I-33 
Appendix I. Quality Ratings of Case-Control Studies, continu

Study, Year Explicit 

definition 

of cases 

Disease 

state of 

the 

cases 

similar & 

reliably 

assessed 

Case 

ascertainment 

reliable, valid 

& applied 

appropriately 

Nonbiased 

selection 

of 

controls 

Cases/controls: 

comparable 

confounding 

factors 

Study 

procedures 

applied 

equally 

Appr

atten

confo

(cons

ad

Rochelson, 2005149 

Yes Yes Yes Unclear Matched on # 

prior cesarean 

otherwise nonmatched 

Yes No

Rouse, 2006150 Yes Yes Unclear Unclear No Unclear Yes

Seidman, 1994151 Yes Yes Unclear Unclear No Unclear Yes

Shimonovitz, 2000152 

No Unclear No Yes Yes Unclear Un

Shipp, 2003153 

Yes Yes Yes Yes Yes Yes Yes

Tikkanen, 2006154 Yes Unclear No No No Unclear Yes

Uygur, 2005155 Yes Yes Yes No No Yes No

Uygur, 2005156 Yes Unclear No No Yes No

Wu, 2005157 Yes Yes No Yes No Unclear Yes

I-34 
Appendix I. Quality Ratings of Case Series Studies
 

Study, Year 

Representative sample 

selected from a 

relevant population 

Explicit definition 

of cases 

Sufficient 

description of 

distribution of 

prognostic factors 

Follow-up long 

enough for 

important events to 

occur 

c

Armstrong, 2004158 

Yes Yes Yes Yes 

Asakura, 2000159 

Unclear Yes Yes Yes 

Blanco, 1992160 Yes Yes No Yes 

Bujold, 2002161 Yes Yes Yes Yes 

Chilaka, 2004162 Yes Yes Unclear Yes 

Gotoh, 2000163 No No Yes Yes 

Grobman, 2007164 

Yes Yes Yes Yes 

Kieser, 2002165 Yes Yes Yes Yes 

Landon, 2005166 Yes Yes Yes Yes 

I-35 
Appendix I. Quality Ratings of Case Series Studies, continu

Study, Year 

Representative sample 

selected from a 

relevant population 

Explicit definition 

of cases 

Sufficient 

description of 

distribution of 

prognostic factors 

Follow-up long 

enough for 

important events to 

occur 

c

Leung, 1993167 Yes Yes Yes Yes 

Lynch, 2002168 Yes Yes Yes Yes 

Meehan, 1989169 

NR NR Somewhat Yes 

Mercer, 2008170 Yes Yes Yes Yes 

Raynor, 1993102 Yes Yes NA NA 

Scott, 2001171 Yes Yes Yes Yes 

Sheiner, 2004172 Yes Yes Unclear Yes 

Shellhaas, 2009 Yes Yes Yes Yes 

Shipp, 2002173 Yes Yes Somewhat Yes 

I-36 
Appendix I. Quality Ratings of Case Series Studies, continu

Study, Year 

Representative sample 

selected from a 

relevant population 

Explicit definition 

of cases 

Sufficient 

description of 

distribution of 

prognostic factors 

Follow-up long 

enough for 

important events to 

occur 

c

Silver, 2006174 Yes Yes Yes Yes 

Stovall, 1987120 Yes Yes No Yes 

Yucel, 2006175] Yes Yes No Yes 

Zelop, 1993176 Yes Yes Yes Yes 

I-37 
Appendix I. Quality Ratings of Cohort Prediction Studies
 

Study, Year 

Comparable 

Groups 

Clear 

inclusion and 

exclusion 

criteria for 

VBAC 

Maintenance 

of 

comparable 

groups 

Clear 

definition 

of 

prognostic 

factors 

Measures 

reliable, 

valid 

Unbiased 

assessment 

of data and 

analysis of 

results 

Loss/ 

Dropout 

rate 

Follow-up 

long 

enough for 

outcomes 

to occur 

c

Bujold, 2001177 No NA Yes Yes/Yes Unclear NA Yes 

Bujold, 200414 Yes NA Yes Yes/Yes Yes NA Yes 

Cameron, 2004178 

Yes NA Yes Yes/Yes No NA Yes 

Chang, 200820 Yes NA Yes Yes/Yes Yes NA Yes 

Costantine, 2009179 

Yes. Unclear 

for twins 

NA Yes Yes/Yes No NA Yes 

Dinsmoor, 200430 

Yes NA Yes Yes/Yes Unclear NA Yes 

Flamm, 199743 Yes NA Yes Yes/Yes Yes NA Yes 

Gonen, 2004180 Yes NA Yes Yes/Yes Unclear NA Yes 

I-38 
Appendix I. Quality Ratings of Cohort Prediction Studies, conti

Study, Year 

Comparable 

Groups 

Clear 

inclusion and 

exclusion 

criteria for 

VBAC 

Maintenance 

of 

comparable 

groups 

Clear 

definition 

of 

prognostic 

factors 

Measures 

reliable, 

valid 

Unbiased 

assessment 

of data and 

analysis of 

results 

Loss/ 

Dropout 

rate 

Follow-up 

long 

enough for 

outcomes 

to occur 

c

c

Grobman, 2007164 

Yes NA Yes Yes/Yes Yes NA Yes 

Gyamfi, 2004181 Yes Yes Yes Yes/Yes Unclear NA Yes 

Harper, 2009182 

(Macones 200581) 

Yes NA Yes Yes/Yes Yes NA Yes 

Hashima, 200758 No. Exclusion 

not defined 

NA Yes Yes/Yes Unclear NA Yes 

Hendler, 2004183 No. Exclusion 

not defined 

Yes Yes Yes/Yes Unclear NA Yes 

Huang, 2002184 No. Exclusion 

not defined 

NA Yes Yes/Yes Unclear NA Yes 

Hueston, 1994185 

No. Exclusion 

not defined. 

NA No Yes/Yes Unclear NA Yes 

Unclear for 

twins 

Grobman, 2007164 

Yes NA Yes Yes/Yes Yes NA Yes 

I-39 
Appendix I. Quality Ratings of Cohort Prediction Studies, conti

Study, Year 

Comparable 

Groups 

Clear 

inclusion and 

exclusion 

criteria for 

VBAC 

Maintenance 

of 

comparable 

groups 

Clear 

definition 

of 

prognostic 

factors 

Measures 

reliable, 

valid 

Unbiased 

assessment 

of data and 

analysis of 

results 

Loss/ 

Dropout 

rate 

Follow-up 

long 

enough for 

outcomes 

to occur 

c

c

Jakobi, 1993186 Yes Yes Yes Yes/Yes No NA Yes 

Kabir, 2005187 Yes NA Yes Yes/Yes NA NA Yes 

King, 1994188 Yes NA Yes Yes/Yes Unclear NA NA 

Landon, 2005166 Yes NA Yes Yes/Yes No NA Yes 

Learman, 1996189 

Yes NA Yes Yes/Yes No NA Yes 

Macones, 2001144

 Unclear how 

controls were 

selected. 

NA Yes Yes/Yes Unclear NA Yes 

Macones, 200581 

Yes NA Yes Yes/Yes Yes NA Yes 

McMahon, 199683 

Yes Yes Yes Yes/Yes Yes NA Yes 

I-40 
Appendix I. Quality Ratings of Cohort Prediction Studies, conti

Study, Year 

Comparable 

Groups 

Clear 

inclusion and 

exclusion 

criteria for 

VBAC 

Maintenance 

of 

comparable 

groups 

Clear 

definition 

of 

prognostic 

factors 

Measures 

reliable, 

valid 

Unbiased 

assessment 

of data and 

analysis of 

results 

Loss/ 

Dropout 

rate 

Follow-up 

long 

enough for 

outcomes 

to occur 

c

c

Mercer, 2008170 Yes NA Yes Yes/Yes NA NA Yes 

Pang, 2009190 Yes Yes Yes Yes/Yes Unclear NA Yes 

Pickhardt, 1992148 

No. Exclusion 

not defined 

NA No Yes/Yes Unclear NA Yes 

Quinones, 200599 

Yes NA Yes Yes/Yes No NA Yes 

Selo-Ojeme, 2008191 

No. Exclusion 

not defined 

NA Yes Yes/Yes No NA Yes 

Shipp, 2000192 Unclear 

comparison 

between 

repeat CD and 

primary CD 

NA Yes Yes/Yes Yes NA Yes 

Smith, 2005193 Yes Yes Yes Yes/Yes No NA Yes 

Spaans, 2002194 Yes NA Yes Yes/Yes No NA Yes 

I-41 
Appendix I. Quality Ratings of Cohort Prediction Studies, conti

Study, Year 

Comparable 

Groups 

Clear 

inclusion and 

exclusion 

criteria for 

VBAC 

Maintenance 

of 

comparable 

groups 

Clear 

definition 

of 

prognostic 

factors 

Measures 

reliable, 

valid 

Unbiased 

assessment 

of data and 

analysis of 

results 

Loss/ 

Dropout 

rate 

Follow-up 

long 

enough for 

outcomes 

to occur 

c

c

Srinivas, 2007195 Yes Yes Yes Yes/Yes Yes NA Yes 

Strong, 1996196 No. Exclusion 

not defined 

Yes Yes Yes/Yes No NA Yes 

Troyer, 1992197 Yes NA Yes Yes/No Unclear NA Yes 

Vinueza, 2000198 Yes NA Yes Yes/No No NA Yes 

Weinstein, 1996127 

Yes NA Yes Yes/Yes Unclear NA Yes 

*Poor quality studies are not included in the narrative or synthesis of the final report, unless no studies of better quality wertopic and/or key question. Abbreviations: CD=cesarean delivery; ERCD=elective repeat cesarean delivery; VBAC=vaginal birth after cesarean 

I-42 
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Appendix J. Strength of Evidence Table 

Domains pertaining to strength of evidence Magnitude of effect 

Strength 

of 

Evidence 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Vaginal Birth After Cesarean 

Rate 

Low, 

Moderate, 

High 

Vaginal Birth After Cesarean Rate 

67 

368,304 

Medium 

16 cohort (Good 

Quality); 

51 cohort (Fair 

Quality) 

Inconsistent Direct for 

delivery 

outcome 

Precise 74% 

(95% CI: 72% to 75%) 

Moderate 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Proportion of Induced Trials 

of Labor 

Low, 

Moderate, 

High 

Any Induction Method in Trial of Labor: Proportion with Vaginal Birth After Cesarean 

28 

11,938 

Medium 

1 RCT, 19 

cohort, 9 case 

series (Fair 

Quality) 

Consistent Direct Precise 63% 

(95% CI: 59% to 67%) 

Moderate 

Prostaglandin E2 Induction in Trial of Labor: Proportion with Vaginal Birth After Cesarean 

5 

1671 

Medium 

11 case series, 4 

cohort (Fair 

Quality) 

Inconsistent Direct Precise 63% 

(95% CI: 58% to 69%) 

Moderate 

Misoprostol Induction in TOL: Proportion with Vaginal Birth After Cesarean 

2 

96 

Medium 

Cohort, (Fair 

Quality) 

Inconsistent Direct Imprecise 61% 

(95% CI: 27% to 90%) Low 

Oxytocin Induction in Trial of Labor: Proportion with Vaginal Birth After Cesarean 

5 

308 

Low 

2 cohort, 3 case 

series (Fair 

Quality) 

Inconsistent Direct Imprecise 62% 

(95% CI: 53% to 70%) 

Low 

Oxytocin Augmentation in Trial of Labor: Proportion with Vaginal Birth After Cesarean 

7 

660* 

Medium 

5 cohort, 2 case 

series (Fair 

Quality) 

Inconsistent Direct Imprecise 68% 

(95% CI: 64% to 72%) 

Low 

Oxytocin verses Prostaglandin E2 Induction in Trial of Labor: Proportion with Vaginal Birth After 

Cesarean 

2 

3301 

1 RCT (Poor 

Quality) 

1 cohort (Fair 

Quality) 

Inconsistent Indirect Imprecise Not applicable Low 

Mechanical Induction in Trial of Labor: Proportion with Vaginal Birth After Cesarean 

Foley 

Catheter 

2 

416 

2 cohort (Fair 

Quality) 

Consistent Direct Imprecise 54% 

(95% CI: 49% to 59%) 

Moderate 

J-1 
Appendix J. Strength of Evidence, continued 

Domains pertaining to strength of evidence Magnitude of effect 

Strength 

of 

Evidence 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Trial of Labor versus Elective 

Repeat Cesarean Delivery 

Low, 

Moderate, 

High 

Maternal Mortality 

14 

405,827 

Medium 

13 cohort (2 

Good, 

11 Fair Quality); 

1 case control 

(Fair Quality) 

Consistent Direct Precise TOL: 3.8/100,000 

(95% CI: 0.9/100,000 to 

15.5/100,000) 

ERCD: 13.4/100,000 

(95% CI: 4.3/100,000 to 

41.6/100,000) 

High 

Maternal Outcomes: Uterine Rupture Rate 

8 

63,499 

Medium 

4 prospective 

cohort; 

4 retrospective 

cohort 

(4 include both 

TOL and ERCD) 

Consistent Direct Precise Overall: 3% 

(95% CI: 0.2% to 0.4%) 

TOL: 0.47% 

(95% CI: 0.28% to 0.68%) 

ERCD: 0.04% 

(95% CI: 0.018% to 0.11%) 

Moderate 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Proportion of Induced Trials 

of Labor 

Low, 

Moderate, 

High 

Any Induction Method in Trial of Labor: Uterine Rupture 

7 

5296 

Medium 

5 cohort, 2 case 

series (Fair 

Quality) 

Inconsistent Direct Imprecise 1.2% 

(95% CI: 0.7% to 1.9%) 

Low 

Prostaglandin E2 Induction in Trial of Labor: Uterine Rupture 

12 6 cohort (5 Fair, 

1 Good Quality) 

6 case series 

(Fair Quality) 

Inconsistent Direct Imprecise 2% 

(95% CI: 1.1% to 3.5%) 

Low 

Misoprostol Induction in Trial of Labor: Uterine Rupture 

1 

226 

Cohort (Fair 

Quality) 

NA Direct Imprecise 13% Low 

Oxytocin Induction in Trial of Labor: Uterine Rupture 

9 

5713 

Medium 

1 case control, 5 

cohort, 3 case 

series (Fair 

Quality) 

Inconsistent Direct Precise 1.1% 

(95% CI: 0.9% to 1.5%) 

Moderate 

Oxytocin Augmentation in Trial of Labor: Uterine Rupture 

Insufficient data to assess 

Oxytocin verses Prostaglandin E2 Induction in Trial of Labor: Uterine Rupture 

1 

3035 

Medium 

1 cohort (Fair 

Quality) 

NA Direct Imprecise Increased risk found in oxytocin 

groups 

Low 

Mechanical Induction in Trial of Labor: Uterine Rupture 

Insufficient data to assess 

Any Induction method in Trial of Labor: Other Harms 

Insufficient data to assess 

J-2 
Appendix J. Strength of Evidence Table, continued 

Domains pertaining to strength of evidence Magnitude of effect 

Strength 

of 

Evidence 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Proportion of Induced Trials 

of Labor 

Low, 

Moderate, 

High 

Prostaglandin E2 Induction in Trial of Labor: Other Harms 

Insufficient data to assess 

Misoprostol Induction in Trial of Labor: Other Harms 

Insufficient data to assess 

Oxytocin Induction in Trial of Labor: Other Harms 

Insufficient data to assess 

Oxytocin Augmentation in Trial of Labor: Other Harms 

Insufficient data to assess 

Oxytocin verses Prostaglandin E2 Induction in Trial of Labor: Other Harms 

Insufficient data to assess 

Mechanical Induction in Trial of Labor: Other Harms 

Insufficient data to assess 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Trial of Labor versus Elective 

Repeat Cesarean Delivery 

Low, 

Moderate, 

High 

Maternal Outcomes: Hysterectomy 

16 

402,059 

Medium 

14 cohort (4 

Good, 

10 Fair Quality); 

1 case control 

(Good Quality) 

Inconsistent Direct Precise Overall: 0.537/1,000 

(95% CI: -1.49/1,000 to 

0.419/1,000) 

TOL: 1.73/1,000 

(95% CI: 0.115/1,000 to 

2.42/1,000) 

ERCD: 3.1/1,000 

(95% CI: 0.172/1,000 to 

4.88/1,000) 

Moderate 

Maternal Outcomes: Transfusion 

10 

409,382 

Medium 

10 cohort (4 

Good, 

6 Fair Quality) 

Consistent Direct Precise Overall: -0.818/1,000 

(95% CI: -0.339/1,000 to 

1.76/1,000) 

TOL: 8.81/1,000 

(95% CI: 4.2/1,000 to 

15.1/1,000) 

ERCD:11.6/1,000 

(95% CI: 6.39/1,000 to 

18.3/1,000) 

Moderate 

Maternal Outcomes: Blood Loss/Hemorrhage 

7 

47,754 

High 

7 cohort (1 

Good, 

6 Fair Quality) 

Inconsistent Indirect Imprecise General trend toward increased 

blood loss with ERCD and RCD 

after a TOL when reported 

Low 

Maternal Outcomes: Effect of Induction on Hemorrhage 

Insufficient data to assess 

J-3 
Appendix J. Strength of Evidence Table, continued 

Domains pertaining to strength of evidence Magnitude of effect 

Strength 

of 

Evidence 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Trial of Labor versus Elective 

Repeat Cesarean Delivery 

Low, 

Moderate, 

High 

Maternal Outcomes: Infection, All Definitions 

22 

354,060 

High 

20 cohort 

(5 Good, 

15 Fair Quality); 

2 case control 

(Fair Quality) 

Inconsistent Indirect Imprecise Overall: 0.93% 

(95% CI: 0.068% to 1.8%) 

TOL: 6.3% 

(95% CI: 3.4% to 10.1%) 

ERCD: 3.9% 

(95% CI: 2.3% to 5.8%) 

Low 

Maternal Outcomes: Fever 

12;26,679 High 

1 cohort (1 

Good, 

11 Fair Quality) 

Inconsistent Direct Imprecise Overall: -5.4% 

(95% CI: -9.9% to -0.80%) 

TOL: 6.6% 

(95% CI: 4.4% to 9.3%) 

ERCD: 10.2% 

(95% CI: 4.9% to 17.1%) 

Low 

Long Term Maternal Outcomes: Adhesions 

Insufficient data to assess 

Long Term Maternal Outcomes: Pelvic Pain 

Insufficient data to assess 

Long Term Maternal Outcomes: Reproductive Health 

Insufficient data to assess 

Infant Outcomes: Perinatal Mortality (infant death occurring ≥20 weeks-28 days life) 

5 

76,899 

Medium 

4 cohort (3 

Good, 1 Fair 

Quality) 

Consistent Indirect Imprecise TOL: 0.00133 

(95% CI: 0.00059 to 0.00034) 

ERCD: 0.00050 

(95% CI: 0.00007 to 0.00382) 

Moderate 

Infant Outcomes: Fetal Mortality (infant death occurring ≥20 weeks gestation, but prior to birth) 

2 

63,646 

Medium 

2 cohort (Good 

Quality, 1with 

AP/IP deaths; 1 

IP only) 

Consistent Indirect Imprecise TOL (overall): 39/30,834 

(1.3/1000) 

ERCD (overall): 23/32,806 

(0.7/1000) 

Low (2 

cohort 

studies) 

Infant Outcomes: Neonatal Mortality (infant death occurring after birth but < 28 days of life) 

6 

108,328 

Medium 

6 cohorts (3 Fair, 

3 Good Quality) 

Consistent Indirect Imprecise TOL: 0.00114 

(95% CI: 0.00063 to 0.00204) 

ERCD: 0.00055 

(95% CI: 0.00020 to 0.00150) 

Moderate 

Term Infant Outcomes: Transient Tachypnea of the Newborn 

3 

4,927 

Medium 

3 cohort (Fair 

Quality) 

Inconsistent Direct Imprecise TOL: 36.1/1,000 

ERCD: 42/1,000 

Low 

Term Infant Outcomes: Neonatal Respiratory Morbidity with Bag & Mask Ventilation 

3 

2,110 

Medium 

3 cohort (Fair 

Quality) 

Inconsistent Direct Imprecise TOL: 53.7/1000 

ERCD: 25/1000 

Low 

J-4 
 

Appendix J. Strength of Evidence Table, continued 

Domains pertaining to strength of evidence Magnitude of effect 

Strength 

of 

Evidence 

# of Studies; 

# of 

Subjects 

Risk of Bias 

(Design/ 

Quality) Consistency Directness Precision 

Trial of Labor versus Elective 

Repeat Cesarean Delivery 

Low, 

Moderate, 

High 

Term Infant Outcomes: Neonatal Respiratory Morbidity with Intubation for Meconium 

2 

1438 

Medium 

2 cohort (Fair 

Quality) 

Consistent Direct Precise TOL: 11.5% 

ERCD: 1.5% 

Moderate 

Term Infant Outcomes: Hypoxic Ischemic Encephalopathy and Asphyxia 

3 

62,829 

High (definition 

issues) 3 cohort 

(Fair Quality) 

Inconsistent Low Imprecise Cannot calculate summary 

estimate 

Low 

Term Infant Outcomes: Neonatal Intensive Care Unit Admissions 

*8 

65,121 

Medium 

8 cohort (2 

Good, 6 Fair 

Quality) 

Inconsistent Indirect Imprecise Cannot calculate summary 

estimate 

Low 

Term Infant Outcomes: Short and Long Term Neurologic Outcomes 

Insufficient data to assess 

Term Infant Outcomes: Confirmed Sepsis 

Insufficient 

data to 

assess 

High (definition 

issues) 

3 cohort (Fair 

Quality) 

Inconsistent Indirect Imprecise Cannot calculate summary 

estimate 

Low 

Term Infant Outcomes: Trauma 

2 

41,899 

High (definition 

issues) 

2 cohort (Fair 

Quality) 

Inconsistent Indirect Imprecise Cannot calculate summary 

estimate 

Insufficient 

Term Infant Outcomes: Breastfeeding 

Insufficient data to assess 

*1 case series included 628 women with induced labor, number with augmentation not reported 

Abbreviations: AP=antepartum; CI=confidence interval; ERCD=elective repeat cesarean delivery; IP=intrapartum; 

RCD=repeat cesarean delivery; TOL=trial of labor 

J-5 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean 

Introduction 

A brief description on the predictors of trial of labor (TOL) and vaginal birth after cesarean 

(VBAC) is included in the text of the evidence report. Detailed descriptions of the studies and 

analyses conducted on these topics are included in this appendix. 

Predictors of Trial of Labor 

Three good quality retrospective cohort studies,1-3 five fair quality retrospective cohort 

studies4-8 and one fair quality retrospective cross sectional study9

 looked for factors known in the 

prenatal setting that may predict TOL. Predictors have been categorized into three categories as 

they relate to the likelihood of TOL: 1) nonclinical which includes the site of care and type of 

insurance 2) demographic which include maternal age, race and economic status and 3) past 

obstetric factors which include a history of a vaginal birth and the gestational age of the prior 

cesarean delivery. Unless otherwise noted, all results are presented in odds ratios. If studies 

reported relative risks (RR), these are noted in the tables. 

Nonclinical Factors 

Among the studies that reported factors related to TOL rates, location of delivery (volume), 

hospital level, and access to private insurance were considered nonclinical factors. 

Three retrospective studies found that the location of delivery was associated with TOL1, 2 or 

related to unnecessary RCDs.9

 In a secondary analysis of the Agency for Healthcare Research 

and Quality’s (AHRQ) 2001 Healthcare Cost and Utilization Project (HCUP) National Inpatient 

Sample database, investigators reported that women had a reduced likelihood of TOL if they 

were delivered in rural or nonteaching urban hospitals (Table K-1).9 These investigators 

identified all women who had unnecessary (had no discharge indication, ICD-9 code, for a repeat 

cesarean delivery [RCD]) RCDs as a way to quantify the number of women who may not have 

been offered a TOL; the database includes data from 33 states. In this study, a prior cesarean 

alone was not considered as sufficient justification for a RCD. With this definition, 65 percent of 

RCDs were considered unnecessary and overall bed size of the hospital was not related to 

unnecessary RCDs. 

In a study of Australian deliveries during 1998 to 2001,1 predictors of TOL were evaluated 

for 14,350 charts of women eligible for TOL by the American College of Obstetricians and 

Gynecologists (ACOG) standards. Women had an increased likelihood of TOL if they delivered 

at a Level 5 or 6 hospital (metro district hospital for high-risk mothers/babies or perinatal center) 

and a decreased likelihood at a Level 4 or below (metro district for moderate-risk 

mothers/babies, rural, and private hospitals).1

 A study conducted in Nova Scotia, Canada, 

between 1986 and 1992, similarly found that women in community and regional hospitals were 

half as likely to have a TOL as women delivering in tertiary care centers.2

 Further examination 

of rural community hospitals suggest that women delivering at rural teaching hospitals with 

lower volumes of deliveries and women with private insurance had a decreased likelihood of 

TOL even when adjusting for race, employment and marital status.7

 Interestingly, the only study 

to date that considered the volume of VBAC deliveries found no relationship between annual 

VBAC volume and rate of TOL (not shown as no odds ratio or RR were provided).5

 In this 

secondary analysis5 of a large, retrospective cohort study,10 55, 51, and 57 percent of women had 

K-1 
 

Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

TOL in hospitals that had less than 70; 70 to 100, or more than 100 VBAC deliveries per year, 

respectively. 

Table K-1. Nonclinical factors as predictors of trial of labor 

Author, Year Characteristic 

Adjusted odds 

ratio for TOL 95% CI 

Site of Care (volume of deliveries) 

Hueston, 19947 

252 women with prior 

CD/2y 1.00 Referent 

135 women with prior 

CD/2 y 0.46 0.29-0.74 

179 women with prior 

CD/2 y 0.57 0.38-0.85 

193 women with prior 

CD/2y 0.38 0.25-0.56 

Hospital Level 

Cameron, 20041 

Level 6 (Perinatal 

center) 1.00 Referent 

Level 5 (High-risk care) 1.22 1.09-1.37 

Level 4 (moderate-risk 

care) 0.90 0.81-0.99 

Level 1-3 (Rural)* 0.66 0.58-0.74 

Private 0.45 0.41-0.50 

McMahon, 19962 

Tertiary Care 1.00 Referent 

Regional Hospital 0.50 0.50-0.60 

Community Hospital 0.40 0.30-0.50 

Private Insurance 

Hueston, 19947

 Yes 0.52 0.35-70 

*96 percent rural hospitals 

Abbreviations: CD=cesarean delivery; CI=confidence interval; TOL=trial of labor; y=year(s) 

Demographic and Pre-Existing Factors 

Studies reported only maternal age, race and economic status as current demographic factors 

affecting rates of TOL. 

Two studies provided evidence that advancing maternal age may change the likelihood of 

TOL (Table K-2).1, 2 In the older of the two studies, conducted between 1986 and 1992, younger 

women (age 19 and younger) and older women (age 30 and older) were more likely to have a 

TOL compared with 25 to 29 year old women.2

 In the second study conducted between 1998 and 

2001, older women were less likely to have a TOL.1

 In contrast to this more recent finding, 

women age 35 and older in a US study conducted in 2001 had a reduced likelihood of an 

unnecessary RCD (or increased likelihood of TOL).9 In this retrospective cross-sectional study 

67 percent of women under age 35 had unnecessary RCDs compared with 60 percent of women 

age 35 and older, p<0.001. 

Two studies found that non-white women had an increased likelihood of a TOL compared 

with white women. In a study based in the United Kingdom (UK) that recorded the rate of TOL 

in 2007, 77 percent of Afro-Caribbean women, 68 percent of Asian women and 41 percent of 

white women chose a TOL.8 In a US study, 66 percent of white women had unnecessary RCDs 

compared with 62 percent of African American women, suggesting that white women had less 

K-2 
 

 

Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

opportunity for a TOL (p<0.001).9 Race in this study was an independent predictor of TOL even 

when type of insurance was included in a regressive model. 

One retrospective study of women in Hong Kong conducted between 2002 and 2006 reported 

social economic factors influenced the decision. When the family monthly income was $3,850 or 

less US dollars, the woman was less likely to choose a TOL (adjusted odds ratio 0.64; 95% CI: 

0.43 to 0.97).3 

Table K-2. Demographic factors as predictors of trial of labor 

Author, Year 

Study Design Characteristic 

Adjusted odds 

ratio for TOL 95% CI 

Maternal Age 

Cameron, 20041 

Retrospective Cohort 

<30 y 1.00 Referent 

30-39 y 0.86 0.80-0.92 

40 y and older 0.40 0.33-0.48 

McMahon, 19962 

Retrospective Cohort 

<19 y 1.40 1.00-2.10 

20-24 y 1.00 0.80-1.10 

25-29 y 1.00 Referent 

30-34 y 1.10 1.00-1.20 

>35 y 1.20 1.00-1.40 

Race 

Selo-Ojeme, 20088 

Retrospective Cohort 

White 1.00 Referent 

Non-white (AfroCaribbean, Asian) 3.5 1.90-6.10 

Abbreviations: CI=confidence interval; TOL=trial of labor; y=year(s) 

Past obstetric factors 

The number of previous vaginal deliveries and gestational age (GA) at prior caesarean 

delivery are the past-obstetric factors that have been assessed for their influence on TOL rates 

Careful attention is given to prior obstetric history in estimating likelihood of VBAC, which, 

in turn may influence the initial decision to have a TOL. Three retrospective cohort studies,1-3 

described above, and a secondary analysis6

 of a large retrospective study10 examined whether 

obstetric factors such as number of prior vaginal deliveries or GA at the prior cesarean predicted 

TOL (Table K-3). The likelihood of TOL increased for women with prior vaginal deliveries1-3 

while it decreased for women who had a prior cesarean before 34 weeks GA.6 

Table K-3. Past obstetric factors as predictors of trial of labor 

Author, Year 

Study Design Characteristic 

Adjusted odds ratio 

or relative risk for 

VBAC 

95% CI 

Number of previous vaginal deliveries 

Cameron, 20041 

Retrospective Cohort 

1 Prior VD 1.51 1.35-1.68 

2 Prior VDs 2.35 1.92-2.86 

> 3 Prior VDs 2.94 2.23-3.88 

McMahon, 19962 

Retrospective Cohort 

1 Prior VD 3.20 Not reported 

2 Prior VDs 4.00 Not reported 

Pang, 2009 

Retrospective Cohort History of VD 6.67 2.70-16.67 

K-3 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-3. Past obstetric factors as predictors of trial of labor 

Author, Year 

Study Design Characteristic 

Adjusted odds ratio 

or relative risk for 

VBAC 

95% CI 

Gestational age of prior cesarean delivery 

Harper, 20096 

Retrospective Cohort 

GA > 34 wk 1 Referent 

GA < 34 wk 1.2 RR 1.1-1.2 

Abbreviations: CI=confidence interval; GA=gestational age; RR=Relative Risk; VBAC=vaginal birth after 

cesarean; VD=vaginal delivery; wk=week(s) 

Summary of Predictors of Trial of Labor 

Trial of labor is more likely in hospitals with higher delivery volumes, tertiary care centers, 

and teaching hospitals. Women with a prior vaginal delivery or non-white women were more 

likely to have a TOL (odds ratio 1.51 to 6.67). 

Predictors of Vaginal Birth After Cesarean 

The impact of individual factors on VBAC discussed in the evidence report can overlap and 

interact with each other such that a factor found to have statistically significant influence on 

VBAC rate may no longer be significant when other key factors are taken into account. Studies 

that evaluate these factors in concert, using regression analyses for example, can provide a higher 

level of evidence on the residual influence of individual factors. Four prospective cohort 

studies,11-14 18 retrospective cohort studies,1, 5, 8, 15-29 and one case-control study30 addressed 

predictive factors for VBAC. The key factors considered by these studies were demographic 

factors that included maternal age, ethnicity, race, and marital status; nonclinical factors that 

included insurance status, site of delivery, and volume of VBACs; past obstetric factors that 

included prior vaginal delivery and prior indications for cesarean; pre-existing and current 

factors that included maternal height, body mass index (BMI), substance abuse, and pre-existing 

maternal disease; and current obstetric factors related to the infant gender, age and size. Finally, 

the section folds in factors related to the labor experience (dilation, effacement, station, Bishop 

score, cervix position, type of labor and epidural use). 

Demographic Factors 

Maternal age, ethnicity, race and marital status have been examined for their ability to predict 

VBAC in women who attempt a TOL (Table K-4). Eight cohort studies provided inconsistent 

evidence on the effect of advancing age on the VBAC rate.1, 11-13, 19, 21, 24, 27 In five of the eight 

studies, younger women were more likely to have a VBAC, particularly women under age 40.1, 

11, 12, 19, 24 In the other studies, there was no statistically significant relationship between maternal 

age and likelihood of VBAC.13, 21, 27 Taken as a group, the overall trend appears to be that 

younger women have a higher likelihood of a VBAC. 

In all four cohort studies reporting on ethnicity and race, Hispanic and African American 

women had a reduced likelihood to have a VBAC compared with non-Hispanic and white 

women, respectively.12, 13, 19, 26 Two large prospective cohort studies reported reduced likelihood 

of VBAC for Hispanic and for African American women (Table K-4).12, 13 In both studies data 

were analyzed from the National Institute of Child Health and Human Development MaternalFetal Medicine Units Network (MFMU, Appendix G). While different subsets of data were 

K-4 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

analyzed based on GA, both studies reached the same conclusions about the effects of race or 

ethnicity on likelihood of VBAC. In one study,13 the VBAC rate was evaluated for women with 

GAs of at least 20 weeks. In this study, Hispanic women were 35 percent less likely to have a 

VBAC and African American women were 31 percent less likely to have a VBAC compared 

with non-Hispanic and white women respectively. 

It is interesting to note that non-white women were more likely to have a TOL but less likely 

to have a VBAC.8 This suggests that other factors related to patient preferences may be driving 

this result. In a prior systematic review,31 underlying cultural ideologies were found to influence 

the desire to go through the painful labor process. Non-white women in 100 structured 

interviews reported that labor was a painful process that did not relate to motherhood.32 By 

contrast, white women in the same cohort study viewed vaginal birth as an experience “not to be 

missed” in motherhood.32 

Additionally, unmarried women had a reduced likelihood of a VBAC.13. Finally, in a 

retrospective study of births in New York in 1989, women with more than 12 years of education 

had an increased likelihood of a VBAC.19 

Table K-4. Demographic factors as predictors of vaginal birth after cesarean 

Author, Year 

Study Design Characteristic 

Adjusted OR for 

VBAC 95% CI 

Maternal age 

Flamm, 199711 

Prospective Cohort >40y 0.39 0.23-0.65 

McNally, 199921 

Retrospective Cohort Per y 1.18 0.98-1.40 

Weinstein, 199627 

Retrospective Cohort >37 y 0.9 0.5-1.7 

Smith, 200524 

Retrospective Cohort Per 5 y increase 0.82 0.78-0.86 

King, 199419 

Retrospective Cohort Per 5 y increase 0.85 0.81-0.90 

Cameron, 20041 

Retrospective Cohort 

<30 y 1.0 referent 

30-39 y 0.86 0.77-0.95 

>40 y 0.59 0.43-0.82 

Grobman, 200712 

Prospective Cohort Per yr 0.96 0.95-0.97 

Landon, 200513 

Prospective Cohort 

<17 y 0.84* 0.57-1.25 

18-34 y 1.0 referent 

>35 y 1.0* 0.91-1.10 

Ethnicity, race and marital status 

Hispanic 

Grobman, 200712 

Prospective Cohort Referent: Non-Hispanic 0.51 0.44-0.59 

Landon, 200513 

Prospective Cohort Referent: Non-Hispanic 0.65* 0.59-0.72 

Srinivas, 200726 

Retrospective Cohort Referent: White 0.69 0.56-0.84 

K-5 
 

Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-4. Demographic factors as predictors of vaginal birth after cesarean 

Author, Year 

Study Design Characteristic 

Adjusted OR for 

VBAC 95% CI 

King, 199419 

Retrospective Cohort Referent: White 0.61 0.51-0.73 

African American 

Grobman, 200712 

Prospective Cohort Referent: White 0.51 0.44-0.59 

Landon, 200513 

Prospective Cohort Referent: White 0.69* 0.63-0.75 

Srinivas, 200726 

Retrospective Cohort Referent: White 0.58 0.52-0.67 

King, 199419 

Retrospective Cohort Referent: White 0.80 0.70-0.93 

Afro-Caribbean 

Selo-Ojeme, 20088 

Retrospective Cohort Referent: White 3.22 1.5-7.14 

Asian 

Srinivas, 200726 

Retrospective Cohort Referent: White 0.80 0.61-1.05 

Other 

Landon, 200513 

Prospective Cohort Referent: White 0.71* 0.60-0.84 

Unmarried 

Landon, 200513 

Prospective Cohort Referent: Married 0.88 0.82-0.95 

Education 

King, 199419 

Retrospective Cohort 

<12 y 1.0 Referent 

12 y 1.15 0.99-1.34 

13-15 y 1.36 1.16-1.60 

16 y 1.59 1.32-1.93 

17 y 2.00 1.64-2.45 

*Only provided univariate odds ratio 

 Abbreviations: CI=confidence interval; OR=odds ratio; VBAC=vaginal birth after cesarean; y=year(s) 

Nonclinical Factors 

Nonclinical factors such as insurance and site of delivery play an important role in deciding 

what kind of birthing options are pursued. Women with non-private insurance or who were 

uninsured had a decreased likelihood for VBAC (Table K-5).13 However, women in Health 

Maintenance Organizations (HMO) had an increased likelihood of VBAC.19 The level of the 

hospital at which the birth takes place is also a major factor in the likelihood of VBAC. Women 

at rural and private hospitals that provide obstetric care for lower risk deliveries had a decreased 

likelihood of VBAC.1

 This finding is consistent with another finding by the same investigators1 

that women at rural and private hospitals were less likely to attempt a TOL. Private hospitals in 

this study had an average VBAC rate of 57 percent compared with a VBAC rate of 66 percent 

for level 6 hospitals.1

 Finally, in a secondary analysis5 of a retrospective cohort study,10 the 

annual VBAC volume at the hospital did not change the likelihood of VBAC. 

K-6 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-5. Nonclinical factors as predictors of vaginal birth after cesarean 

Author, Year 

Study Design Characteristic 

Adjusted OR for 

VBAC 95% CI 

Insurance Status 

Landon, 200513 

Prospective Cohort 

Private 1.00 Referent 

Non-private 0.88* 0.81-0.95 

Uninsured 0.74* 0.66-0.83 

King, 199419 

Retrospective Cohort 

Private 1.00 Referent 

HMO 1.15 1.02-1.30 

Self-pay 1.19 0.96-1.47 

Medicaid 1.01 0.89-1.15 

Hospital Level of Birth 

Cameron, 20041 

Retrospective Cohort 

Level 6 (Perinatal center) 1.0 Referent 

Level 5 (High-risk care) 0.96 0.82-1.12 

Level 4 (Moderate-risk 

care) 1.02 0.89-1.19 

Level 1-3 (Rural†

) 0.79 0.65-0.95 

Private 0.72 0.62-0.84 

Volume of VBACs 

Chang, 20085 

Retrospective Cohort 

<70 per year 1.11 0.79-1.56 

70-100 per year 1.16 0.93-1.45 

>100 per year 1.00 Referent 

*Only provided univariate odds ratio 

†

96 percent rural hospitals 

Abbreviations: CI=confidence interval; HMO=health management organization; OR=odds ratio; 

VBAC=vaginal birth after cesarean 

Past obstetric Factors 

There is particular interest in whether demographic factors, nonclinical and past obstetric 

factors may predict VBAC since these factors are known prenatally and would allow clinicians 

to provide information on prognosis early in pregnancy. Investigators from studies have explored 

prior vaginal delivery, years since prior cesarean delivery, prior labor experience and prior baby 

weight as potential factors for predicting VBAC. A prior history of vaginal delivery was 

consistently reported to increase likelihood of VBAC in all 13 cohort studies (Table K-6).1, 11-13, 

15, 17, 18, 20, 21, 24, 26, 27, 33 in one case-control study30 Women with a vaginal delivery after their prior 

cesarean (prior VBAC) were three to seven times more likely to have a VBAC for their current 

delivery11-13, 15, 17, 18, 30, 33 compared with women with no prior VDs. Women who had a vaginal 

delivery before their cesarean deliveries also had an increased likelihood to have a VBAC.11, 27 

One secondary analysis of a retrospective cohort study10 of 16 community and university 

hospitals that is not included in Table K-6 because it did not provide odds ratios34 specifically 

examined the effect of prior vaginal delivery before a cesarean and of a prior VBAC on the 

current TOL. The VBAC rate for women with no history of vaginal delivery was 65 percent, 83 

percent for women with a prior vaginal delivery before a cesarean, and 94 percent for women 

with a prior VBAC.34 Finally, a secondary analysis of the MFMU cohort data reported that the 

likelihood of a VBAC increased with each prior VBAC.35 Women with zero, one, two, three, and 

four or more prior VBACs had likelihoods of VBAC of 63.3, 87.6, 90.9, 90.6, and 91.6 percent 

(p<0.001), respectively. 

K-7 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-6. Past obstetric factor as predictors of vaginal birth after cesarean: prior 

deliveries 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR for 

VBAC 95% CI 

Multipara/vaginal delivery 

Learman, 199620 

Retrospective Cohort Yes 03.45 RR 1.0-12.50 RR 

Prior vaginal delivery 

McNally, 199921 

Retrospective Cohort Yes 27.78 3.85-200 

Grobman, 200712 

Prospective Cohort Yes 2.43 2.04-2.89 

Landon, 200513 

Prospective Cohort Yes 3.90 3.60-4.30 

Smith, 200524 

Retrospective Cohort Yes 5.08 4.82-5.72 

Cameron, 20041 

Retrospective Cohort 

1 prior 2.95 2.47-3.53 

2 prior 5.58 3.92-7.96 

3 prior 3.57 2.43-5.26 

Bujold, 200415 

Retrospective Cohort Yes 2.69 1.41-5.13 

Srinivas, 200726 

Retrospective Cohort Yes 4.76 4.17-5.26 

Gyamfi, 200418 

Retrospective Cohort 

Spontaneous 

vaginal delivery 1.83 1.29-2.60 

Vaginal delivery before prior cesarean 

Flamm, 199711 

Prospective Cohort Yes 1.53 1.12-2.10 

Weinstein, 199627 

Retrospective Cohort Yes 1.8 1.1-3.1 

Vaginal delivery after prior cesarean 

Flamm, 199711 

Prospective Cohort Yes 3.39 2.25-5.11 

Macones, 200130 

Case Control Yes 7.69 3.23-20 

Gonen, 200417 

Retrospective Cohort Yes 7.20 2.10-24.80 

Grobman, 200712 

Prospective Cohort Yes 2.73 2.21-3.36 

Landon, 200513 

Prospective Cohort 

No 1.0 referent 

Yes 4.76* 4.35-5.26 

Bujold, 200415 

Retrospective Cohort Yes 3.32 1.35-8.13 

Gyamfi, 200418 

Retrospective Cohort Yes 7.40 4.51-12.16 

K-8 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-6. Past obstetric factor as predictors of vaginal birth after cesarean: prior 

deliveries 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR for 

VBAC 95% CI 

Vaginal delivery after prior cesarean versus vaginal delivery before prior cesarean 

Caughey, 199833 

Retrospective Cohort Yes 3.48 1.9-6.1 

Vaginal delivery before and vaginal delivery after prior cesarean 

Flamm, 199711 

Prospective Cohort Yes 9.11 2.2-38.0 

*Only provided univariate odds ratio 

Abbreviations: CI=confidence interval; OR=odds ratio; RR=relative risk when odds ratio not reported; 

VBAC=vaginal birth after cesarean 

In examining the indication for the prior cesarean delivery, the evidence suggested an 

association between a prior indication of breech and a VBAC (Table K-7). One retrospective 

study17 showed that a prior cesarean delivery due to malpresentation (breech) significantly 

increased likelihood of VBAC (adjusted odds ratio 7.4; 95% CI: 2.8 to19.2, compared with an 

indication for failure to progress [FTP]) and a second retrospective study27 suggested a 

relationship that was not statistically significant (adjusted odds ratio 1.0; 95% CI: 1.0 to 3.6 

compared to a non-breech indication). Consistent with these findings, a third retrospective 

study23 reported that women with a prior breech indication had the same risk of a RCD as a 

nulliparous woman’s risk of a primary cesarean (risk of RCD odds ratio 0.95; 95% CI: 0.70 to 

1.30). 

This same study reported that women with a prior indication of FTP were four times (odds 

ratio 4.50; 95% CI: 3.60 to 5.50) as likely to have a RCD when compared with the risk of a 

nulliparous woman to have a primary cesarean.23 This finding supports the trend shown in Table 

K-7 that a prior indication of FTP reduces the likelihood of a VBAC.11, 20, 27 

The evidence on prior indications for dystocia, FTP or for fetal concern was inconsistent in 

predicting VBAC.13, 15, 20, 25, 27 Cervical ripening with a Foley catheter was also reported in one 

study15 to reduce likelihood of VBAC (adjusted odds ratio 0.6; 95% CI: 0.40 to 0.89) compared 

with a fetal indication. 

In considering other factors about the prior cesarean delivery, two studies found no 

relationship in the spacing of deliveries: less than 19 months36 or less than 2 years13 compared to 

larger inter-delivery spacing. Compared with women who had an unknown scar, women with a 

LTCS had a reduced likelihood of VBAC (univariate odds ratio 0.71; 95% CI: 0.64 to 0.79).13 

Finally, Women who delivered prior babies greater than 4,000 grams, were less likely to have a 

VBAC (adjusted odds ratio 0.52; 95% CI: 0.32 to 0.85).15 

K-9 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-7. Past obstetric factor as predictors of vaginal birth after cesarean: prior 

indications 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR for 

VBAC 95% CI 

Recurring versus nonrecurring 

Weinstein, 199627 

Retrospective Cohort 

Referent: 

Nonrecurring 0.80 0.3-2.0 

Grobman, 200712 

Prospective Cohort 

Referent: 

Nonrecurring 

indication for arrest 

in dilation or 

descent 

0.53 0.48-0.60 

Gyamfi, 200418 

Retrospective Cohort 

Referent: 

Nonrecurring 0.42 0.31-0.57 

Mal-presentation (breech) 

Weinstein, 199627 

Retrospective Cohort Yes 1.9 1.0-3.6 

Gonen, 200417 

Retrospective Cohort Referent: FTP 7.40 2.8-19.2 

Dystocia 

Landon, 200513 

Retrospective Cohort Referent: Breech 0.59 0.56-0.67 

Bujold, 200415 

Retrospective Cohort 

1st stage of labor 

Referent: fetal 

indication 

0.5 0.34-0.74 

Bujold, 200415 

Retrospective Cohort 

2nd stage of labor 

Referent: fetal 

indication 

0.97 0.50-1.88 

Cephalopelvic disproportion 

Srinivas, 200726 

Retrospective Cohort Any CPD 0.69 0.63-0.77 

Failure to progress 

Weinstein, 199627 

Retrospective Cohort FTP 0.81 0.3-2.0 

Learman, 199620 

Retrospective Cohort FTP 0.83 (RR) 0.36-1.67 

Flamm, 199711 

Prospective Cohort FTP 0.52 0.43-0.63 

Spaans, 2002 

Retrospective Study 

FTE or suspected 

cephalic pelvic 

distortion 

0.34 0.15-0.77 

Cervical ripening with foley catheter 

Bujold, 200415 

Retrospective Cohort 

Referent: fetal 

indication 0.60 0.40-0.89 

Fetal wellbeing 

Landon, 200513 

Prospective Cohort 

Non-reassuring 

fetal well-being 

Referent: Breech 

0.51* 0.45-0.58 

K-10 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-7. Past obstetric factor as predictors of vaginal birth after cesarean: prior 

indications 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR for 

VBAC 95% CI 

Weinstein, 199627 

Retrospective Cohort Fetal Distress 1.05 0.4-2.6 

*Only univariate odds ratio provided 

Abbreviations: CI=confidence interval; CPD=cephalopelvic disproportion; FTP=failure to progress; 

OR=odds ratio; RR=Relative Risk; VBAC=vaginal birth after cesarean 

Pre-Existing and Current Obstetric Factors 

Many pre-existing factors (maternal height, BMI, smoking and substance use, and maternal 

disease) greatly impact the likelihood of VBAC (Table K-8). In examining pre-existing factors, 

women with greater maternal height (for each 5 cm increase) had an increased likelihood of 

VBAC.24 Increased BMI at the first prenatal visit (per BMI unit)12 or an increased BMI at 

delivery (greater than 30) resulted in decreased likelihood of VBAC.13 Women who smoked or 

reported any substance abuse had an increased likelihood of VBAC but neither study adjusted for 

socioeconomic status.13, 30 However, in three of four cohort studies in Table K-8, women with a 

maternal disease (hypertension, diabetes, asthma, seizures, renal disease, thyroid disease, or 

collagen vascular disease) had a decreased likelihood of VBAC.13, 18, 26 By contrast, in a large 

prospective study by Grobman et al,12 the presence of diabetes, asthma, chronic hypertension, 

renal disease or heart disease, was not significant in the study’s multivariable logistic model. 

Table K-8. Pre-existing maternal factors predicting vaginal birth after cesarean 

Author, Year 

Study Design Characteristic 

Adjusted OR for 

VBAC 95% CI 

Maternal height 

Smith, 200524 

Retrospective Cohort Per 5 cm increase 1.33 1.28-1.37 

BMI at first prenatal visit 

Grobman, 200712 

Prospective Cohort Per BMI unit 0.94 0.93-0.95 

BMI at delivery 

Landon, 200513 

Prospective Cohort >30 0.55* 0.51-0.60 

Smoking 

Landon, 200513 

Prospective Cohort Smoker 1.15* 1.04-1.28 

Substance Abuse 

Macones, 200130 

Case Control Yes 3.70 1.25-11.11 

Maternal disease 

Srinivas, 200726 

Retrospective Cohort Chronic hypertension 0.70 0.56-0.86 

Srinivas, 200726 

Retrospective Cohort Gestational diabetes 0.68 0.58-0.81 

Grobman, 200712 

Prospective Cohort Diabetes Not significant Not significant 

Gymafi, 200418 

Retrospective Cohort 

Diabetes or gestational 

diabetes 0.42 0.28-0.62 

K-11 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-8. Pre-existing maternal factors predicting vaginal birth after cesarean 

Author, Year 

Study Design Characteristic 

Adjusted OR for 

VBAC 95% CI 

Landon, 200513 

Prospective Cohort 

Hypertension, diabetes, 

asthma, seizures, renal 

disease, thyroid disease, 

or collagen vascular 

disease. 

0.83 0.71-0.71 

Grobman, 200712 

Hypertension, cardiac 

disease, asthma, renal 

disease, or connective 

tissue disorder 

Not reported Not reported 

*Only univariate odds ratio provided 

Abbreviations: BMI=body mass index; CI=confidence interval; cm=centimeters; OR=odds ratio; 

VBAC=vaginal birth after cesarean 

Many current obstetric factors related to the infant (GA, birth weight and infant gender) 

predicted VBAC or TOL followed by a cesarean delivery (Table K-9). Of these, the most 

consistent finding is that as infant weight increases the likelihood of VBAC decreases. Four of 

five studies reported that infants weighing more than 4 kilograms (kg) were less likely to be 

delivered vaginally.1, 13, 18, 27, 28 The oldest of these studies27 found no relationship between a 

birth weight over 4,000 grams and likelihood of VBAC. 

Table K-9. Current obstetric factors: infant gender, gestational age, and weight 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR 

for VBAC 95% CI 

Gestational age 

Srinivas, 200726 

Retrospective Cohort 

37-41 wk 1.00 Referent 

<32 wk 2.32 1.67-3.33 

32-37 wk 1.37 1.14-1.67 

>41 wk 1.25 1.10-1.41 

Cameron, 20041 

Retrospective Cohort 

40 wk 1.00 Referent 

37 wk 0.43 0.34-0.54 

38 wk 0.51 0.44-0.60 

39 wk 0.74 0.65-0.85 

41 wk 0.89 0.77-1.04 

Landon, 200513 

Prospective Cohort 

37 0/7-40 6/7 wk/d 1.00 Referent 

>41 wk 0.61* 0.55-0.68 

Smith, 200524 

Retrospective Cohort 

40 wk 1.00 Referent 

41 wk 0.77 0.7-0.85 

42 wk 0.72 0.62-0.85 

Gonen, 200417

 >41 wk 0.36 0.14-0.91 

Learman, 199620 

Retrospective Cohort >41 wk 1.25 (*RR) 0.53-3.33 

Quiñones, 200522 

Retrospective Cohort 

33.9 wk 1.54 1.27-1.86 

39.2 wk 1.0 Referent 

Gestational age and labor 

Zelop, 200128 Retrospective 

Cohort >40wks spontaneous 0.67 0.56-0.83 

K-12 
 

Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-9. Current obstetric factors: infant gender, gestational age, and weight 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR 

for VBAC 95% CI 

Zelop, 200128 Retrospective 

Cohort >40wks induced 0.67 0.45-0.91 

Birth weight 

Weinstein, 199627 

Retrospective Cohort >4000g 1.05 0.20-5.88 

Zelop, 200128 

Retrospective Cohort >4000g 0.59 0.45-0.77 

Gyamfi, 200418 

Retrospective Cohort >4000g 0.49 0.30-0.78 

Cameron, 20041 

Retrospective Cohort 

3000-3499g 1.0 Referent 

<2500g 0.66 0.45-0.97 

2500-2999g 0.93 0.78-1.10 

3500-3999g 0.75 0.66-0.85 

>4000g 0.54 0.46-0.64 

Landon, 200513 

Prospective Cohort >4000g 0.50 0.43-0.56 

Mean estimated fetal weight 

Gonen, 200417 

Prospective Cohort 3360g + 395 0.9 0.8-0.9 

Learman, 199620 

Retrospective Cohort >3800g 0.53 (*RR) 0.24-1.11 

Sex of Infant 

Smith, 200524 

Retrospective Cohort Female 1.18 1.08-1.28 

*Only univariate odds ratio provided 

Abbreviations: CI=confidence interval; d=day(s); g=gram(s); kg=kilogram(s); OR=odds ratio; RR=relative 

risk; VBAC=vaginal birth after cesarean; wk= week(s); 

Obstetric factors related to the labor itself (dilation, effacement, station, Bishop score, cervix 

position) consistently predicted VBAC (Table K-10). Three prospective cohort studies,11, 13, 17 

one retrospective study20 and one case-control study30 provided consistent evidence that women 

who were more dilated at admission or at rupture of membranes (ROM) were more likely to 

deliver vaginally. All three studies that examined effacement reported increased likelihood as 

effacement reached 75 to 100 percent.11, 17, 21 Similarly, all three studies that examined head 

position reported that as the baby’s position was vertex, engaged or at a lower station, the 

likelihood of VBAC increased.14, 19, 20 Both studies that examined Bishop’s score showed that as 

the score increased the likelihood of VBAC increased two15 to six times.27 

Table K-10. Current obstetric factors: cervical dilation, etc 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR 

for VBAC 95% CI 

Cervical dilation at admission 

Flamm, 199711 

Prospective Cohort >4cm 2.16 1.66-2.82 

Landon, 200513 

Prospective Cohort >4cm 2.56* 2.38-2.78 

K-13 
 

Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-10. Current obstetric factors: cervical dilation, etc 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR 

for VBAC 95% CI 

Macones, 200130 

Case Control Per cm increase 1.89 1.13-3.22 

Gonen, 200417 

Prospective Cohort >2cm 3.00 1.70-5.30 

Learman, 199620 

Retrospective Cohort >2cm 1.69 (*RR) 0.80-3.45 RR 

Effacement 

Flamm, 199711 

Prospective Cohort 

>75% 

Referent: <25% 2.72 2.00-3.71 

Flamm, 199711 

Prospective Cohort 

25-75% 

Referent: <25% 1.79 1.31-2.44 

McNally, 199921 

Retrospective Cohort 100% 5.0 1.28-19.2 

Head position and station 

King, 199419 

Retrospective Cohort Head in vertex position 7.69 5.26-12.5 

Strong, 199614 

Prospective Cohort 

Head engaged on 

admission 12.3 4.6-33.3 

Learman, 199620 

Retrospective Cohort Lower than -3 cm 2.10 (*RR) 1.10-4.20 RR 

Bishop score 

Weinstein, 199627 

Retrospective Cohort >4 6.00 3.5-10.4 

Bujold, 200415 

Retrospective Cohort >6: modified 2.07 1.28-3.35 

*Only univariate odds ratio provided 

Abbreviations: CI=confidence interval; cm=centimeters; OR=odds ratio; RR: relative risk; VBAC=vaginal 

birth after cesarean 

Other obstetric factors related to interventions (augmentation, induction, or epidural use) 

were examined in predicting VBAC (Table K-11). Three studies consistently showed reduced 

likelihood of VBAC with augmentation.13, 17, 30 Two studies13, 20 showed that induction reduced 

the likelihood of VBAC and three more studies showed the same trend.17, 24, 25 One of these 

studies showed no effect when a non-prostaglandin was used but showed a reduced likelihood of 

VBAC if a prostaglandin was used.24 

The overall evidence suggests that epidurals reduced the likelihood of VBAC17, 21 but is not 

completely consistent with one study showing an increased likelihood of VBAC.13 

Table K-11. Current obstetric factors: type of labor 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR 

for VBAC 95% CI or P value 

Augmentation 

Macones, 200130 

Case Control Yes 0.47 0.25-0.88 

Landon, 200513 

Prospective Cohort Referent: Spontaneous 0.68* 0.62-0.75 

K-14 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

Table K-11. Current obstetric factors: type of labor 

Author, Year 

Study Design Characteristic 

Adjusted OR* or RR 

for VBAC 95% CI or P value 

Gonen, 200417 

Prospective Cohort 

Augmentation with 

oxytocin 0.29 0.16-0.53 

Spaans, 200225 

Retrospective Cohort Yes 0.83 0.30-2.50 

Induction 

Gonen, 200417 

Prospective Cohort 

On admit 

Referent: in labor and 

ROM 

0.6 0.3-1.5 

Gonen, 200417 

Prospective Cohort During labor 0.5 0.23-1.11 

Landon, 200513 

Prospective Cohort Referent: Spontaneous 0.5* 0.45-0.55 

Learman, 199620 

Retrospective Cohort Yes 0.34 (*RR) 0.19-0.67 RR 

Spaans, 200225 

Retrospective Cohort Yes 0.67 0.16-3.33 

Smith, 200524 

Retrospective Cohort 

IOL: Non-prostaglandin 

Referent: Spontaneous 1.00 0.87-1.14 

Smith, 200524 

Retrospective Cohort 

IOL: With prostaglandin 

Referent: Spontaneous 0.70 0.63-0.79 

Epidural use 

McNally, 199921 

Retrospective Cohort Yes 0.26 0.06-1.12 

Landon, 200513 

Prospective cohort Yes 2.70* 2.44-3.03 

Gonen, 200417 

Prospective Cohort Yes 0.17 0.09-0.35 

*Only univariate odds ratio provided 

Abbreviations: CI=confidence interval; IOL=induction of labor; OR=odds ratio; ROM=rupture of 

membranes; RR=relative risk; VBAC=vaginal birth after cesarean 

Summary of Predictors of Vaginal Birth After Cesarean 

With the exception of three studies,11, 12, 24 these prognostic studies of VBAC could be 

described as exploratory.37 According to Simon and Altman, studies that report association and 

identify patients at risk but that have not yet had results confirmed in followup studies with prestated hypotheses, do not yet provide sufficient evidence to change clinical practice.37 The three 

studies11, 12, 24 that provided this cross-validation evidence also proposed screening tools for 

VBAC and are discussed in detail in the section on Screening Tools for VBAC and in Appendix 

N. 

Summary of Predictors 

Hispanic and African American women were more likely to have a TOL but less likely to 

have a VBAC compared with non-Hispanic and white women, respectively. Women at rural and 

private hospitals had a decreased likelihood of TOL and a decreased likelihood of VBAC. A 

K-15 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

prior history of vaginal delivery was consistently reported to increase likelihood of VBAC. 

Women delivering infants over 4 kg have a reduced likelihood of VBAC. Greater progress of 

labor--measured as greater dilation, lower station and higher Bishop score--predicts a higher 

likelihood of VBAC. The effect of epidural use on the likelihood of VBAC is uncertain. 

K-16 
Appendix K. Detailed Evaluation of Predictors of Trial of 

Labor and Vaginal Birth After Cesarean, continued 

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K. Interdelivery interval and the 

success of vaginal birth after 

cesarean delivery. Obstet Gynecol. 

2002;99(1):41-44. 

37. Simon R, Altman D. Statistical 

aspects of prognostic factor studies 

in oncology. Br J Cancer. 

1994;69:979-985. 

K-19 
Appendix L. Detailed Evaluation of Vaginal Birth After 

Cesarean Rates 

Introduction 

A brief description on the vaginal birth after cesarean (VBAC) rate is included in the text of 

the evidence report. Detailed descriptions of the studies and analyses conducted on this topic are 

included in this appendix. 

Vaginal Birth After Cesarean 

Sixty-seven studies, 14 fair quality prospective cohort studies1-14 and 53 retrospective cohort 

studies15-67 provided an overall summary estimate for VBAC of 74 percent (95 percent CI: 72 to 

75 percent). The heterogeneity of this meta-analysis of 67 observational studies that included 

368,304 women was high, I

2

 greater than 98 percent. To examine this heterogeneity, these 

studies were stratified and analyzed by study design (prospective versus retrospective; true 

cohort that included trial of labor (TOL) and elective repeat cesarean delivery (ERCD) versus 

studies of TOL only), country (United States [U.S.] versus non-U.S.), gestational age ([GA] term 

only versus all GAs) and by years when the data were collected (completed before 1996, during 

1996, and started after 1996). None of these factors were found to result in statistically 

significant differences analysis of study design yielded a statistically significant association 

(p<0.05). The summary estimate for VBAC for 14 prospective studies was 73 percent (95 

percent CI: 71 to 74 percent) compared with 77 percent (95 percent CI: 75 to 79 percent) for the 

53 retrospective studies. The VBAC rate did not differ between studies that included both TOL 

and ERCD groups and those that focused exclusively on TOL (73 percent; 95 percent CI: 71 to 

75 percent versus 74 percent; 95 percent CI 71 to 77 percent).Similarly when studies were 

stratified by country (U.S. versus Non-U.S.) and by GA at enrollment (term versus non-term 

studies), no clear associations emerged (Figures L-1 and L-2). The summary estimates for rates 

of VBAC were similar: for the 43 studies conducted in the U.S., 74 percent (95 percent CI: 72 to 

76 percent) versus 73 percent (95 percent CI: 71 to 74 percent) for the 24 studies conducted 

outside the U.S.. In examining the GA for enrolled patients, the summary estimates for rates of 

VBAC were again similar: for the 18 studies of term deliveries, 73 percent (95 percent CI: 71 to 

75 percent) versus 74 percent (95 percent CI: 72 to 76 percent) for the 49 studies that included 

preterm and term deliveries. 

L-1 
0.77 (0.72, 0.82) 

0.81 (0.78, 0.84) 

0.74 (0.72, 0.76) 

0.82 (0.80, 0.83) 

0.79 (0.75, 0.84) 

0.61 (0.55, 0.68) 

0.83 (0.78, 0.88) 

0.67 (0.59, 0.76) 

0.76 (0.71, 0.81) 

0.68 (0.63, 0.73) 

0.61 (0.47, 0.74) 

0.75 (0.73, 0.76) 

0.85 (0.80, 0.90) 

0.75 (0.73, 0.77) 

0.64 (0.61, 0.66) 

0.75 (0.73, 0.76) 

0.61 (0.61, 0.62) 

0.81 (0.79, 0.82) 

0.63 (0.58, 0.69) 

0.69 (0.68, 0.71) 

0.76 (0.69, 0.83) 

0.66 (0.62, 0.70) 

0.66 (0.62, 0.70) 

0.87 (0.85, 0.89) 

0.79 (0.76, 0.82) 

0.77 (0.75, 0.80) 

0.75 (0.75, 0.76) 

0.78 (0.76, 0.79) 

0.73 (0.73, 0.74) 

0.75 (0.75, 0.76) 

0.74 (0.71, 0.77) 

0.73 (0.67, 0.78) 

0.68 (0.64, 0.72) 

0.75 (0.68, 0.82) 

0.85 (0.83, 0.87) 

0.74 (0.73, 0.75) 

0.77 (0.72, 0.82) 

0.77 (0.75, 0.79) 

0.81 (0.78, 0.83) 

0.76 (0.75, 0.76) 

0.85 (0.83, 0.87) 

0.64 (0.63, 0.65) 

0.67 (0.66, 0.68) 

0.52 (0.48, 0.57) 

0.73 (0.70, 0.77) 

0.74 (0.72, 0.76) 

 

 

 

Appendix L. Detailed Evaluation of Vaginal Birth After 

Cesarean Rates, continued 

Figure L-1. Vaginal birth after cesarean rates in United States studies 

Study Name 95% Confidence Interval 

Any gestational age N
 

Horenstein, 1984 292
 

Horenstein, 1985 732 

Flamm,1987 1776 

Phelan,1987 1796 

Stovall, 1987 272 

Yetman, 1989 224 

Sakala, 1990 237 

Johnson,1991 110 

Nguyen, 1992 242 

Pickhardt, 1992 312 

Raynor,1993 51 

Flamm,1994 5022 

Learman,1996 175 

Ouzounian,1996 1436 

Hoskins,1997 1917 

Caughey, 1999 3891 

Gregory, 1999 39096 

Socol, 1999 2082 

Vinueza, 2000 263 

Zelop, 2001 2775 

Dinsmoor, 2004 153 

Durnwald, 2004b 522 

Durnwald,2004a 510 

Lieberman, 2004 1106 

Goodall, 2005 725 

Juhasz,2005 1213 

Macones,2005 13617 

Hollard, 2006 2575 

Landon,2006 17898 

DeFranco, 2007 13698 

Subtotal 

Term 

Troyer, 1992 264 

Hook, 1997 492 

DiMaio,2002 139 

Huang,2002 1185 

Elkousy, 2003 9960 

Fisler, 2003 313 

Gyamfi, 2004 1216 

Loebel,2004 927 

Hibbard,2006 15780 

El-Sayed, 2007 1284 

Hashima,2007 16767 

Gregory, 2008 11480 

Costantine, 2009 502 

Subtotal 

(Total) overall 

0 .4 .6 .8 1 

Vaginal birth after cesarean rate (95% confidence interval) 

L-2 
0.60 (0.46, 0.73) 

0.82 (0.78, 0.87) 

0.60 (0.59, 0.62) 

0.75 (0.71, 0.78) 

0.77 (0.71, 0.83) 

0.78 (0.74, 0.82) 

0.62 (0.55, 0.68) 

0.78 (0.72, 0.84) 

0.77 (0.71, 0.83) 

0.71 (0.64, 0.79) 

0.65 (0.64, 0.66) 

0.73 (0.72, 0.74) 

0.76 (0.74, 0.77) 

0.75 (0.73, 0.76) 

0.79 (0.77, 0.81) 

0.63 (0.60, 0.66) 

0.79 (0.70, 0.88) 

0.80 (0.77, 0.82) 

0.80 (0.77, 0.83) 

0.73 (0.70, 0.77) 

0.75 (0.74, 0.75) 

0.72 (0.71, 0.72) 

0.74 (0.73, 0.75) 

0.49 (0.39, 0.59) 

0.70 (0.66, 0.74) 

0.72 (0.70, 0.74) 

0.73 (0.71, 0.74) 

 

 

 

Appendix L. Detailed Evaluation of Vaginal Birth After 

Cesarean Rates, continued 

Figure L-2. Vaginal birth after cesarean rates in studies conducted outside the United States 

Study Name N 95% Confidence Interval 

Any gestational age 

van Gelderen, 1986 52 

Jakobi, 1993 

McMahon, 1996 

Rozenberg, 1996 

Strong, 1996 

Weinstein, 1996 

Obara, 1998 

Rozenberg, 1999 

Bais, 2001 

Spaans, 2002 

Cameron, 2004 

DeLaney, 2003 

Hammoud, 2004 

Hendler, 2004 

Locatelli, 2004 

Yogev, 2004 

Pathadey, 2005 

Gonen, 2006 

Kugler, 2008 

Subtotal 

Term 

Smith, 2002 

Wen, 2004 

Smith, 2005 

Selo-Ojeme, 2008 

Pang, 2009 

Subtotal 

(Total) Overall 

261 

3249 

517 

195 

471 

214 

185 

184 

147 

6983 

3746 

2493 

2204 

1321 

1028 

81 

841 

774 

15515 

128960 

23286 

92 

478 

0 .4 .6 .8 1 

Vaginal birth after cesarean rate (95% confidence interval) 

Finally, when the studies were stratified by years of data collection, the summary estimates 

of VBAC again remained similar: 73 percent (95 percent CI: 70 to 77 percent) for the 31 studies 

completed before 1996;1, 2, 5, 8-14, 16, 26, 27, 30, 36-38, 43, 47-50, 53-55, 59, 61, 63, 65, 67, 68; 74 percent (95 percent 

CI: 72 to 76 percent) for the 19 studies that included data collection during 19963, 19, 22-25, 32-34, 42, 

44-46, 52, 57, 58, 60, 62, 64 and 73 percent (95 percent CI: 70 to 75 percent) for the 17 studies started 

after 1996.4, 6, 7, 15, 17, 18, 20, 21, 28, 29, 31, 35, 39, 41, 51, 56, 66

 Summary of vaginal Birth After Cesarean Rate 

The rates of VBAC are highly variable in these studies. Most evidence of VBAC rates are 

from studies based in large tertiary care centers. While TOL rates have dropped over time, 

VBAC rates reported in observational studies have remained constant for the women who have a 

TOL. In studies based in the U.S., 74 percent of women who had a TOL delivered vaginally. 

L-3 
Appendix L. Detailed Evaluation of Vaginal Birth After 

Cesarean Rates, continued 

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L-5 
Appendix L. Detailed Evaluation of Vaginal Birth After 

Cesarean Rates, continued 

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L-6 
Appendix L. Detailed Evaluation of Vaginal Birth After 

Cesarean Rates, continued 

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L-8 
percent Augmented with oxytocin

 

 

Appendix M. Induction of Labor Additional Figures 

Figure M-1. Proportion with vaginal birth after cesarean and any method of induction of labor 

Study Name 

Any gestational age
 

Blanco, 1992
 

Chilaka, 2004
 

DelValle, 1994
 

Kayani, 2005
 

Meehan, 1988
 

Umeadi, 2007
 

Flamm, 1997
 

Hammoud, 2004
 

Horenstein, 1984
 

Horenstein, 1985
 

Ben-Aroya, 2002
 

Locatelli, 2004
 

Bujold, 2004
 

Pathadey, 2005
 

Rageth, 1999
 

Sakala, 1990
 

Flamm, 1987
 

Van Gelderen, 1986
 

Yogev, 2004
 

Agnew, 2009
 

Overall
 

Term 

Goldberger, 1989
 

Norman, 1992
 

Silver, 1987
 

Hammoud, 2004
 

Gibson, 1988
 

Grobman, 2007
 

Zelop, 1999
 

Overall
 

Term randomized 

controlled trial 

Rayburn, 1999
 

Overall 

(Total) overall 

N 

25
 

130
 

89
 

205
 

127
 

17
 

453
 

685
 

58
 

289
 

216
 

310
 

672
 

59
 

2,459
 

48
 

485
 

22
 

97
 

421
 

6,867
 

19
 

30
 

34
 

441
 

10
 

3,259
 

560
 

4,353 

143
 

143
 

0.1 VBAC rate (95% confidence interval) 

VBAC Rate (95% 

Confidence Interval) 

0.720 (0.518, 0.860) 

0.500 (0.415, 0.585) 

0.640 (0.536, 0.733) 

0.522 (0.454, 0.590) 

0.740 (0.657, 0.809) 

0.235 (0.091, 0.486) 

0.514 (0.468, 0.560) 

0.692 (0.656, 0.725) 

0.534 (0.407, 0.658) 

0.692 (0.636, 0.743) 

0.519 (0.452, 0.584) 

0.710 (0.657, 0.758) 

0.695 (0.659, 0.729) 

0.678 (0.549, 0.784) 

0.656 (0.637, 0.674) 

0.583 (0.441, 0.713) 

0.637 (0.593, 0.679) 

0.636 (0.423, 0.807) 

0.639 (0.539, 0.728) 

0.786 (0.744, 0.823) 

0.634 (0.595, 0.671) 

0.842 (0.608, 0.948) 

0.733 (0.550, 0.861) 

0.629 (0.365, 0.688) 

0.730 (0.687, 0.770) 

0.600 (0.297, 0.842) 

0.664 (0.648, 0.680) 

0.382 (0.343, 0.423) 

0.637 (0.502, 0.753) 

0.573 (0.491, 0.652) 

NaN (NaN, NaN) 

0.628 (0.589, 0.665) 

1
 

Abbreviations: NaN=Not a number; VBAC=vaginal birth after cesarean 

M-1 
 

 

 

Appendix M. Induction of Labor Additional Figures, 

continued 

Figure M-2. Proportion with vaginal birth after cesarean after induction of labor with prostaglandin 

E2 

Any gestational age: 

cohort 

Study Name 

Any gestational age: 

case series 

Any gestational age: 

randomized controlled trial 

Term: 

case series 

(Total) overall 

N VBAC Rate (95% 

Confidence Interval) 

Ardiet, 2005 

Blanco, 1992 

Chilaka, 2004 

DelValle, 1994 

Flamm, 1997 

Kayani, 2005 

Locatelli, 2006 

Meehan, 1988 

Umeadi, 2007 

Overall 

144 

25 

130 

36 

453 

97 

310 

52 

17 

1,264 

55 

34 

97 

54 

240 

Ben-Aroya, 2002 

Pathaday, 2005 

Yogev, 2004 

Agnew, 2009 

Overall 

0.639 (0.557, 0.713) 

0.720 (0.518, 0.860) 

0.608 (0.521, 0.688) 

0.694 (0.528, 0.688) 

0.514 (0.468, 0.560) 

0.464 (0.367, 0.563) 

0.710 (0.657, 0.758) 

0.788 (0.657, 0.879) 

0.235 (0.091, 0.486) 

0.612 (0.527, 0.691) 

0.545 (0.414, 0.671) 

0.676 (0.505, 0.811) 

0.639 (0.539, 0.728) 

0.741 (0.609, 0.840) 

0.646 (0.565, 0.720) 

19 

30 

49 

Goldberger, 1989 

Norman, 1992 

Overall 

0.842 (0.608, 0.948) 

0.733 (0.550, 0.861) 

0.770 (0.631, 0.868) 

143 

143 

Rayburn, 1999 

Overall 

0.573 (0.491, 0.687) 

NaN (NaN, NaN) 

0.633 (0.575, 0.687) 

0 1 

VBAC rate (95% confidence interval) 

Abbreviations: NaN=Not a number; VBAC=vaginal birth af ter cesarean 

M-2 
 

 

 

 

 

Appendix M. Induction of Labor Additional Figures, 

continued 

Figure M-3. Vaginal birth after cesarean rates with oxytocin augmentation 

Study Name N 95% Confidence Interval 

(Term: cohort) 

(Term : case series) 

(Any gestational 

age: cohort) 

(Any gestational
 

age: cohort)
 

(Any gestational 

age: cohort) 

(Any gestational
 

Age: cohort)
 

(Total) overall 

Vaginal birth after cesarean rate (95% confidence interval) 

M-3 
Appendix N. Detailed Evaluation of Screening Tools for 

Predicting Vaginal Birth After Cesarean 

Introduction 

A brief description on the screening tools for predicting vaginal birth after cesarean (VBAC) 

is included in the text of the evidence report. Detailed description of the studies and analyses 

conducted on this topic is included in this appendix. 

Screening Tools for Predicting Vaginal Birth After Cesarean 

The purpose of a screening tool is to help providers and patients to better identify who will 

have a VBAC (and who is more likely to have a repeat cesarean delivery [RCD]). Two 

prospective cohort studies,1, 2 ten retrospective cohort studies3-12 and two case-control studies13, 14 

that presented screening tools were identified. All included studies were either good or fair 

quality (Table N-1). These studies combined individual factors to predict the likelihood of 

VBAC (or cesarean delivery) when certain thresholds were reached. Predictive variables 

(historic, intrapartum or perinatal) of delivery route were first identified by univariate analyses. 

Significant variables (p<0.05) were included in multiple logistic regression models and/or scored 

models. 

In the strongest studies, the resulting models or scoring systems were then evaluated with a 

separate validation data set.15 Three of the scored models presented at the top of Table N-1 had 

one or more external validation studies (shaded) that tested the models with independent cohort 

data sets. The scored model by Flamm et al1

 was externally validated by one retrospective cohort 

study.5

 The scored model by Grobman et al2 was externally evaluated with a retrospective study.4 

The Troyer model was externally validated by two retrospective studies.5, 11 In all validation 

studies, the scored model’s performance was similar to the originally reported performance. In a 

retrospective cohort study that evaluated three scored models using the same data set,1, 10, 16, 

Dinsmoor et al reported that all three models were accurate at predicting which women would 

have a VBAC but were not accurate at predicting who would have a RCD after a TOL. Using the 

three models, 50 percent of women with unfavorable risk factors (in these three models) had 

vaginal deliveries suggesting that other factors may be needed to identify women at risk for 

cesarean. A previous decision analysis of VBAC17 suggested that a scored model would be most 

useful clinically if it achieved a sensitivity and specificity over 85 percent5

 which none of these 

tools achieved. 

In four studies, a cross-validation approach was taken.1, 2, 7, 9 The data in these studies were 

randomly divided to create a score development group and a validation group. In a multi-center 

prospective cohort study by Flamm,1

 48 percent of women were assigned VBAC estimates either 

below 60 percent or greater than 80 percent suggesting that almost half of the women gained new 

information after the screening. After being screened by the tool that included maternal age, prior 

vaginal delivery history, prior cesarean delivery indication, cervical effacement and dilation, 18 

percent of women in the validation group had a less than 60 percent likelihood of VBAC which 

might discourage some of these women from attempting a TOL. Thirty percent of the women in 

the validation group had an estimated 87% likelihood of VBAC, which might prove to encourage 

more of these women to attempt a TOL. 

N-1 
Appendix N. Detailed Evaluation of Screening Tools for Predicting Vagi

Cesarean, continued 

Table N-1. Screening tools for predicting vaginal birth after cesarean 

Design Years TOL/ Predictors included 

Author/Year Population Eligible Score development (point values if provided) Perfo

Flamm, Prospective 5003/ Half of the population for score Age <40 years: 2 pts, prior vaginal In vali

199718 cohort 5022 development and the other for delivery (prior to CD: 1pt, VBAC: 2 VD

1990-1992 score validating. Logistic pts, both: 4 pts), prior cesarean 0 to 2 Prior LTCS All GA 

modeling of significant variables at the univariate level. Scores based on beta coefficients. 

indication (other than FTP: 1 pt), cervical effacement (25-75%: 1 pt, >75%: 2 pt), cervical dilation (>4cm at admission: 1pt) to predict 

3 59.9 4 66.7 5 77.0 6 88.6 7 92.6 VBAC. 8 to 10 

Dinsmoor, Retrospective 153/153 Applied Flamm scored model Age <40 years: 2 pts, prior vaginal Score 20045 Cohort 

1998 

(validation study) delivery (prior to CD: 1pt, VBAC: 2 

pts, both: 4 pts), prior cesarean 

>7 100 < 4 56 

Prior CD indication (other than FTP: 1 pt), All GA cervical effacement (25-75%: 1 pt, 

>75%: 2 pt), cervical dilation (>4cm at admission: 1pt) to predict VBAC. 

Grobman, Prospective 11,856/ Half of the population randomly Maternal age, pre-pregnancy BMI, In valid

200719 cohort 11,856 selected for score development prior VD, prior VBAC, recurring 

1999-2002 and the other for score indication for CD to predict VBAC. 1 LTCS validating. Logistic modeling of Term significant variables at the 

univariate level. Scores based on beta coefficients. 

Costantine, Retrospective 502/502 Applied Grobman 2007 scored Maternal age, pre-preg BMI, prior Correc

20094 2002-2007 

Prior CD GA > 36 wks 

model (validation study) VD, prior VBAC, recurring 

indication for CD to predict VBAC. 

women 60% oAURO

Troyer, Retro cohort 264/567 Univariate analysis identified Previous dysfunctional labor, no Score 199210 1990-1991 variables significantly associated prior vaginal delivery, non- 0 91.5 

Term Prior LTCS 

GA > 36 wks Vertex 

with trial of labor outcome. Onepoint per variable. reassuring FHT at admission, induction (1 pt each) to predict 

VBAC. 

1 73.9 2 66.7 3-4 46
Appendix N. Detailed Evaluation of Screening Tools for Predicting Vagi

Cesarean, continued 

Table N-1. Screening tools for predicting vaginal birth after cesarean 

Design Years TOL/ Predictors included 

Author/Year Population Eligible Score development (point values if provided) Perfo

Dinsmoor, Retrospective 153/153 Applied Troyer scored model Previous dysfunctional labor, no Score 

20045 Cohort (validation study) prior vaginal delivery, non- 0 97 

1998 reassuring FHT at admission, 3 56 Prior CD induction (1 pt each) to predict All GA VBAC. 

Vinueza, Retro cohort 236/236 Applied Troyer screening tool Previous dysfunctional labor, no Score 

200011 1992-1997 

Prior LTCS All GA 

(validation study). prior vaginal delivery, nonreassuring FHT at admission, 

induction (1 pt each) to predict VBAC. 

0 98 1 69 2 40 3-4 33 

Weinstein, Retro cohort 471/572 Logistic regression analysis to Bishop score (>4: 4 pts), vaginal Score 199612 1981-1990 obtain weighted scores based on delivery before cesarean: 2 pts), > 4 58 

Israel 1 prior CD 

All GA 

odds ratios. prior cesarean indication (multiple 

grades ranging in values of 3-6 pts) to predict VBAC. 

> 6 67 > 8 78 > 10 8> 12 8For > Spec:6Accura

Jakobi, 19938 Retro cohort 261/261 Univariate analysis coupled with Prior breech, prior VBAC, station, PV for 

Israel Years NR multivariate analysis and admission without ROM, dilation at PV for 

1 prior CD discriminant analysis. admission, prior failure to AccuraNo oxytocin prorgress to predict VBAC. All GA 

Gonen, Retro cohort 339/475 Univariate analysis coupled with Indication of first CD (0-3 pts), Score 

20046 Isreal 2000 

1 LTCS All GA 

logistic regression analysis. previous VBAC (3 pts), diliation > 2 

cm (2 pts), gestation (< 41 wks, 2 pts) to predict VBAC. 

0-2 42 3-6 81 7-10 9PV for 88.2%Accura
Appendix N. Detailed Evaluation of Screening Tools for Predicting Vagi

Cesarean, continued 

Table N-1. Screening tools for predicting vaginal birth after cesarean 

Design Years TOL/ Predictors included 

Author/Year Population Eligible Score development (point values if provided) Perfo

Hashima, Retro cohort, 10, 828/ Half of the population randomly Non-recurrent prior CD indication, In valid

20077 180-2002 10,828 selected for score development no history of macrosmic, no VD

1 LTCS and the other for score maternal anemia to predict VBAC. 0 25.0 Term validating. Logistic modeling of 

significant variables at the univariate level. Scores based on 

1 48.5 2 52.9 3 66.9 

beta coefficients. 

Smith, 20059 Retro cohort 

1985-2001 1 LTCS Term 40-42 wks 

23,286/ 23,286 

Half of the population randomly selected for score development and the other for score validating. Logistic modeling of significant variables at the univariate level. Scores based on beta coefficients. 

Maternal age, prior vaginal delivery, GA (40, 41, 42), induction method, gender of infant to convert prior odds to posterior odds of CD. 

In validwomen for CD 89.1%predict(>40% 89.1%model weeks

Bujold, 20043 Retro cohort, 

1988-2002 Induction after prior LTCS > 24 wks 

685/685 Logistic modeling of significant 

variables at the univariate level. Scores based on beta coefficients. 

Bishops score. Cervical dialation (0-6 points); effacement (0-3 points); fetal station (0-3 points) to predict VBAC. 

 Score 0-2 573-5 646-8 829-11 9

Macones, Case Control 400/400 Cases: TOL-CD History of substance abuse, prior Sens:7200113 1994-1998 

Prior CD all GA 

Controls: VBAC Univariate analysis coupled with multivariate modeling. 

VBAC, admission cervical dilation, need for labor augmentation to predict CD. 

AURO

Pickhardt, Case control 312/336 Cases: TOL-CD Equation 1: EFW, number of prior Equati199214 1989 Controls: VBAC cesarean to predict CD. Sens:6

Prior CD Univariate analysis coupled with Equation 2: number of prior Accuraall GA stepwise regression, resulting in 

two different models. 

cesarean, cervical dilation, estimated GA to predict CD. 

EquatiSens:3Accura

Abbreviations: AUROC=area under the Receiver Operating Characteristic curve; CD=cesarean delivery; FHT=fetal heart to

age; LTCS=low transverse cesarean scar; VBAC=vaginal birth after cesarean section; VD=vaginal delivery; wks=weeks 

NOTE: Shaded rows are validation studies of a scored model presented above them. 
 

Appendix N. Detailed Evaluation of Screening Tools for 

Predicting Vaginal Birth After Cesarean, continued 

In a retrospective study designed to predict risk of cesarean delivery for women at 40 to 42 

weeks gestational age (GA),9 16.5 percent of women were assigned estimates of cesarean greater 

than 40 percent based on a screening tool that included maternal age, GA, induction method and 

gender of the infant. In the same study, 36 percent of women were assigned estimates of cesarean 

less than 20 percent, again suggesting that more than half of women gained knowledge after 

being screened. 

The remaining two cross-validated studies2, 7 evaluated tools based on factors that are known 

before labor begins in women who delivered at term. In a retrospective study of a statewide 

population database, women in this study with any of the following—recurrent cesarean delivery 

indication, history of a macrosmic infant, or current anemia—had a likelihood of VBAC of less 

than 55 percent. In the prospective cohort study,2 women were screened based on maternal age, 

pre-pregnancy BMI, race, ethnicity, prior vaginal delivery history, and recurring indication for 

cesarean delivery. These factors were then used to create a graphical nomogram. This nomogram 

not only provided a point estimate for VBAC but also 95 percent confidence interval around the 

estimate. The authors present four case studies using the nomogram (two in which the women 

are assigned estimates in the expected range of 60 to 80 percent; and two in which the estimates 

are outside the quoted range). In one case, a 25 year-old African American woman of prepregnancy body mass index (BMI) of 25, with a prior vaginal delivery and a prior VBAC, was 

assigned an estimate of VBAC of 92.4 percent (95% CI: 91.1 to 93.6 percent). In a second case, 

a 35 year-old white woman with a pre-pregnancy BMI of 30, with no prior vaginal delivery and a 

recurring cesarean indication received an estimate of 49 percent (95% CI: 46.1 to 51.9 percent). 

In evaluating the performance of screening tools, the studies report inconsistent accuracy for 

predicting overall delivery route (Gonen, 2004: 84.3 percent;6 Weinstein, 1996: 80 percent;12 

Macones, 2001: 71.9 percent;13 Jakobi, 1993: 68 percent8). It is important to note in looking at 

Table N-1, that most studies are designed to predict VBAC. The ability of these tools to identify 

women best suited for VBAC is noted by sensitivity levels12 and positive predictive values.6, 8 

The only study to report sensitivity, the proportion of women who delivered vaginally who were 

correctly categorized to deliver vaginally, achieved a sensitivity of 85.5 percent.12 Two studies 

reported high positive predictive values for VBAC (Jakobi, 1993: 94.5 percent8

 and Gonen, 

2004: 88.2 percent6), meaning that about 90 percent of women predicted to have a vaginal birth 

from the tools actually had a vaginal birth. These same studies were not as accurate at predicting 

cesarean delivery with predictive values (for cesarean) ranging from 33.3 percent8

 to 58.1 

percent.6 

Other studies are modeled to predict cesarean delivery (RCD after a TOL).9, 13, 14 In these 

studies high levels of specificity mean the model is reasonable at estimating the proportion of 

women who had a VBAC who were identified to have a VBAC.9, 13, 14 Specificity across these 

studies ranged from 65 percent13 to 89 percent.9 These studies had inconsistent ability to identify 

women at risk for cesarean as shown by sensitivity levels ranging from 3814 to 77 percent.13 

Three of the studies evaluated the screening tool performance by examining the area under 

the Receiver Operating Characteristic curve (AUROC).2, 9, 13 This curve is a plot of the truepositive rate (sensitivity) against the false-positive rate (1-specificity). Screening tools with more 

area under the ROC are considered better tests. The AUROC ranged from 699

 to 77 percent.13 

N-5 
Appendix N. Detailed Evaluation of Screening Tools for 

Predicting Vaginal Birth After Cesarean, continued 

Summary of Screening Tools to Predict Vaginal Birth After Cesarean 

Since the last VBAC report,20 five new scored models have been created and evaluated to 

identify women for VBAC (or for RCD).2, 3, 6, 7, 9 Two of the studies created scored tools that can 

be used the prenatal setting.2, 7 All scored models provide reasonable ability to identify women 

who are good candidates for VBAC but none have discriminating ability to consistently identify 

women who are at risk for cesarean. 

N-6 
 

 

 

 

Appendix N. Detailed Evaluation of Screening Tools for 

Predicting Vaginal Birth After Cesarean, continued 

References 

1.	 Flamm BL, Geiger AM. Vaginal birth after 

cesarean delivery: an admission scoring 

system. Obstetrics & Gynecology. 

1997;90(6):907-910. 

2.	 Grobman WA, Lai Y, Landon MB, et al. 

Development of a nomogram for prediction 

of vaginal birth after cesarean delivery. 

Obstetrics & Gynecology. 2007;109(4):806-

812. 

3.	 Bujold E, Blackwell SC, Hendler I, Berman 

S, Sorokin Y, Gauthier RJ. Modified 

Bishop's score and induction of labor in 

patients with a previous cesarean delivery. 

American Journal of Obstetrics & 

Gynecology. 2004;191(5):1644-1648. 

4. Costantine MM, Fox K, Byers BD, et al. 

Validation of the prediction model for 

success of vaginal birth after cesarean 

delivery. Obstetrics and Gynecology. 

2009;114(5):1029-1033. 

5.	 Dinsmoor MJ, Brock EL. Predicting failed 

trial of labor after primary cesarean delivery. 

Obstetrics & Gynecology. 2004;103(2):282-

286. 

6.	 Gonen R, Tamir A, Degani S, Ohel G. 

Variables associated with successful vaginal 

birth after one cesarean section: a proposed 

vaginal birth after cesarean section score. 

American Journal of Perinatology. 

2004;21(8):447-453. 

7.	 Hashima JN, Guise J-M. Vaginal birth after 

cesarean: a prenatal scoring tool. American 

Journal of Obstetrics & Gynecology. 

2007;196(5):e22-23. 

8.	 Jakobi P, Weissman A, Peretz BA, 

Hocherman I. Evaluation of prognostic 

factors for vaginal delivery after cesarean 

section. Journal of Reproductive Medicine. 

1993;38(9):729-733. 

9.	 Smith GCS, White IR, Pell JP, Dobbie R. 

Predicting cesarean section and uterine 

rupture among women attempting vaginal 

birth after prior cesarean section. PLoS 

Medicine / Public Library of Science. 

2005;2(9):e252. 

10.	 Troyer LR, Parisi VM. Obstetric parameters 

affecting success in a trial of labor: 

designation of a scoring system. American 

Journal of Obstetrics & Gynecology. 

1992;167(4 Pt 1):1099-1104. 

11. Vinueza CA, Chauhan SP, Barker L, 

Hendrix NW, Scardo JA. Predicting the 

success of a trial of labor with a simple 

scoring system. Journal of Reproductive 

Medicine. 2000;45(4):332-336. 

12. Weinstein D, Benshushan A, Tanos V, 

Zilberstein R, Rojansky N. Predictive score 

for vaginal birth after cesarean section. 

American Journal of Obstetrics & 

Gynecology. 1996;174(1 Pt 1):192-198. 

13.	 Macones GA, Hausman N, Edelstein R, 

Stamilio DM, Marder SJ. Predicting 

outcomes of trials of labor in women 

attempting vaginal birth after cesarean 

delivery: a comparison of multivariate 

methods with neural networks. American 

Journal of Obstetrics & Gynecology. 

2001;184(3):409-413. 

14. Pickhardt MG, Martin JN, Jr., Meydrech EF, 

et al. Vaginal birth after cesarean delivery: 

are there useful and valid predictors of 

success or failure? American Journal of 

Obstetrics & Gynecology. 1992;166(6 Pt 

1):1811-1815; discussion 1815-1819. 

15. Altman D. Prognosis and prognostic 

research: validating prognostic model. BMJ. 

2009;338:1430-1435. 

16. Alamia VJ, Meyer BA, Selioutski O, Vohra 

N. Can a VBAC scoring system predict 

uterine rupture in patients attempting a trial 

of labor? Paper presented at: ACOG 47th 

Annual Clinical Meeting; May 19, 1999. 

17. Macones GA. The utility of clinical tests of 

eligibility for a trial of labour following a 

caesarean section: a decision analysis. 

British Journal of Obstetrics & 

Gynaecology. 1999;106(7):642-646. 

18. Flamm BL. Once a cesarean, always a 

controversy. Obstetrics & Gynecology. 

1997;90(2):312-315. 

19. Grobman WA, Gilbert S, Landon MB, et al. 

Outcomes of induction of labor after one 

prior cesarean. Obstetrics & Gynecology. 

2007;109(2 Pt 1):262-269. 

N-7 
Appendix N. Detailed Evaluation of Screening Tools for 

Predicting Vaginal Birth After Cesarean, continued 

20.	 Guise JM, McDonagh MS, Hashima J, et al. 

Vaginal birth after cesarean (VBAC). 

Evidence Report: Technology Assessment. 

2003(71):1-8. 

N-8 
Appendix O. Detailed Maternal Mortality Table 

Table O-1. Maternal mortality rates for trial of labor versus elective repeat cesarean delivery among any gestationaAuthor, year Study description N 

Overall maternal death (followed by death per 100,000) 

Maternal death by delivery type (death per 100,000

Term gestational age Gregory, 20081 Retrospective cohort 

Low risk = absence of maternal complications High Risk = any maternal condition ICD9 codes 

41,450 2/41,450 (0.005%) 

Overall: 5/100,000 Low-risk 1/29,126 (0.003%) 3/100,000 High-risk 1/12,324 (0.008%) 8/100,000 

Low-risk TOL: 0/8,292 (0%) RCD: 1/20,834 (0.4.7/100,000 High-risk TOL: 0/3,188 (0%) ERCD: 1/9,136 (010.9/100,000 

Loebel 20042 Retrospective Cohort 

Community Teaching Hospital 

1,408 0/1,408 (0%) TOL: 0/927 

ERCD: 0/481 

Spong,20073 MFMU Network 

cohort 19 University hospitals 

39,117 6/39,117 (0.015%) 

15/100,000 

TOL: 1/15,323 (0.06.5/100,000 ERCD: (no indicat5/14,993 (0.033%) 33.3/100,000 All other groups: 0 

Wen, 20044 Retrospective cohort 

Canadian Registry ICD9 codes 

308,755 12/308,755 (0.004%) 

4/100,000 

TOL: 2 /128,960 (015/100,000 ERCD: 10/179,795 5.6/100,000 

Any gestational age Bais, 20015 Prospective Cohort 

Netherlands Regional hospital 

252 0/252 (0%) 

O-1

TOL: 0/184 ERCD: 0/68 

Eglinton 19846 Retrospective cohort 

University Hospital 

871 1/871 (0.115%) 

115/100,000 

TOL:0/308 ERCD: 1/563 117.6/100,000 

Eriksen, 19897 Retrospective Cohort 

Military Base 

139 0/139 (0%) TOL: 0/71 

ERCD: 0/68 

Flamm, 19948 Prospective cohort 

10 Kaiser Hospital in CA 

7,229 1/7229 (0.014%) 

14/100,000 

TOL 1/5022 (0.02020/100,000 ERCD: 0/2208 (0%

Martin, 19839 Prospective Cohort 

2 University Centers 

709 0/709 (0%) TOL: 0/162 

ERCD: 0/547 
Appendix O. Detailed Maternal Mortality Table, continued 

Table O-1. Maternal mortality rates for trial of labor versus elective repeat cesarean delivery among any gestationaAuthor, year Study description N 

Overall maternal death (followed by death per 100,000) 

Maternal death by delivery type (death per 100,000

Obara, 199810 Prospective Cohort University 

Hospital, Japan 

310 0/310 (0%) TOL: 0/214 

ERCD:0/96 

Phelan,198711 Prospective Cohort 

University hospital >2 prior CD only 

2,643 2/2643 (0.076%) 

76/100,000 

TOL: 1/1796 (0.0555.7/100,000 RCD: 1/847 (0.118118/100,000 

Zelop, 199912 Retrospective Cohort 

University Hospital 

2,774 0/2774 (0%) Not reported 

Abbreviations: CA=California; CD=cesarean delivery; ERCD=elective repeat cesarean delivery; ICD-9= International Class

9th Edition/Revision; MFMU=Maternal Fetal Medicine Units; RCD=repeat cesarean delivery; TOL=trial of labor 
Appendix O. Detailed Maternal Mortality Table 

References 

1. Gregory KD, Korst LM, Fridman M, 

et al. Vaginal birth after cesarean: 

clinical risk factors associated with 

adverse outcome. Am J Obstet 

Gynecol. 2008;198(4):452.e451-410; 

discussion 452.e410-452. 

2. Loebel G, Zelop CM, Egan JFX, 

Wax J. Maternal and neonatal 

morbidity after elective repeat 

Cesarean delivery versus a trial of 

labor after previous Cesarean 

delivery in a community teaching 

hospital. J Matern Fetal Neonatal 

Med. 2004;15(4):243-246. 

3. Spong CY, Landon MB, Gilbert S, et 

al. Risk of uterine rupture and 

adverse perinatal outcome at term 

after cesarean delivery. Obstet 

Gynecol. 2007;110(4):801-807. 

4. Wen SW, Rusen ID, Walker M, et al. 

Comparison of maternal mortality 

and morbidity between trial of labor 

and elective cesarean section among 

women with previous cesarean 

delivery. Am J Obstet Gynecol. 

2004;191(4):1263-1269. 

5. Bais JM, van der Borden DM, Pel M, 

et al. Vaginal birth after caesarean 

section in a population with a low 

overall caesarean section rate. Eur J 

Obstet Gynecol Reprod Biol. 

2001;96(2):158-162. 

6. Eglinton GS, Phelan JP, Yeh S, Diaz 

FP, Wallace TM, Paul RH. Outcome 

of a trial of labor after prior cesarean 

delivery. J Reprod Med. 

1984;29(1):3-8. 

7. Eriksen NL, Buttino L, Jr. Vaginal 

birth after cesarean: a comparison of 

maternal and neonatal morbidity to 

elective repeat cesarean section. Am 

J Perinatol. 1989;6(4):375-379. 

8. Flamm BL, Goings JR, Liu Y, 

Wolde-Tsadik G. Elective repeat 

cesarean delivery versus trial of 

labor: a prospective multicenter 

study. Obstet Gynecol. 

1994;83(6):927-932. 

9. Martin JN, Jr., Harris BA, Jr., 

Huddleston JF, et al. Vaginal 

delivery following previous cesarean 

birth. Am J Obstet Gynecol. 

1983;146(3):255-263. 

10. Obara H, Minakami H, Koike T, 

Takamizawa S, Matsubara S, Sato I. 

Vaginal birth after cesarean delivery: 

results in 310 pregnancies. J Obstet 

Gynaecol Res. 1998;24(2):129-134. 

11. Phelan JP, Clark SL, Diaz F, Paul 

RH. Vaginal birth after cesarean. Am 

J Obstet Gynecol. 1987;157(6):1510-

1515. 

12. Zelop CM, Shipp TD, Repke JT, 

Cohen A, Caughey AB, Lieberman 

E. Uterine rupture during induced or 

augmented labor in gravid women 

with one prior cesarean delivery. Am 

J Obstet Gynecol. 1999;181(4):882-

886. 

O-3 

O-3 
Appendix P. Predictive Tools of Uterine Rupture Table 

Table P-2. Predictive tools of uterine rupture Author, year, country 

Study years/ Population 

# UR/ population Score development 

Predictors 

included 

(point values if 

provided) Factors , OR, and score S

Shipp, Retrospective 40/4,383 Score development only Maternal age (<30, Factor OR (95%CI) Score S

20081 Cohort TOLs 30-39; >40) Age>40 5.8 (1.6-20.3) 2 U

US 1984-1996 

TOL among prior cesarean (4% among women with >1 CD) 

interdelivery interval >18 months having > 1 prior cesarean number of prior VDs 

Age 30-39 2.6 (1.1-6.0) 1 >2 prior CD 5.3 (2.1-12.9) 2 Interdelivery 2.4 (1.0-5.6) interval 1 Prior VD 0.3 (0.1-0.9) -1 

-0 1 2 3 4 O0

Macones Secondary 134 cases At least 17 factors "No individual Factor OR (95%CI) Beta A

, 20062 Analysis of UR (670 examined and analyzed factors are Coefficient A

USA Nested CaseControl 

(nested in retrospective cohort) identified by ICD9 code 1996-2000 

controls)/25 ,000 TOLs Cases: UR TOL Controls: no UR TOL 

using Chi square, unpaired t-tests and the MannWhitney U test. Those significant at p<0.1 were included in two regression models using backwards stepwise elimination: antepartum and early intrapartum factors Final model selected by ROC characteristics 

sufficient" Mat Age 1.11 (1.05-1.17) 

0.05 GA at deliv 1.12 (0.97-1.20) 0.11 Ethnicity .84 (.74-1.0) -0.43 Prior VD .40 (.20-.80) -0.83 Cerv dil >3cm .66 (.41-1.11) -0.39 IOL 1.94 (1.32-2.81) 0.59 

InAAosFO0
Appendix P. Predictors of Uterine Rupture Table, continue

Table P-2. Predictive tools of uterine rupture Author, year, country 

Study years/ Population 

# UR/ population Score development 

Predictors 

included 

(point values if 

provided) Factors , OR, and score S

Smith, Retrospective 101 Score Development and Factor for Emergent CD OR P

20053 Cohort UR/23,386 Validation Groups (95%CI) a

Scotland 1985-2001 

National Dataset hosp discharge and perinatal deaths Designed to look at unplanned CD (UR secondary) 40-43wks GA 

1 prior CD Mat Age (5yr inc) 1.22 

(1.16-1.28) Mat Ht (5cm inc) 0.75 (0.73-0.78) Male infant 1.18 (1.08-1.29) Prior VD 0.19 (0.17- 0.22) - 1/5.08 (4.52-5.72) GA .66 

EO0

Grobman Cohort 83 Logistic Regression of Maternal age, "Predictive nomogram was R

, 20084 MFMU 

Cesarean registry 1999-2002 1 prior LTCD >37 weeks looked for factors known prenatally or at admission 

UR/11,855 LTCD TOL 

factors associated with UR (20 factors) Divided population into development and testing populations ROC generated from regression and c statistic was determined Partitioned UR into 10 groups 0-0.5% 0.5-1.0% ... 4.5-5.0% 

ethnicity, BMI, Medical HX: recurrent indication for CD, time since last CD, N prior VD, VD before CD, prior PTD, prior birth wt, GDM, asthma, CHTN, connective tissue disorder Intrapartum: IOL, IOL indication, cervical exam, EGA, PIH 

not developed because it would have little clinical value" Factor OR (95%CI) Any prior VD 0.44 (0.27-0.71) IOL 1.71 (1.11-2.69) Best Model to predict UR exp(w)/[1+exp(w)], where w=-4.81-0.82(previous VD) + 0.55(IOL) 

0"dpeO

Abbreviations: CD=cesarean delivery; CHTN=chronic hypertension; CI=confidence interval; cm=centimeter; EGA= estimat

GA=gestational age; GDM=gestational diabetes mellitus; IOL=induction of labor; LTCD=low transverse cesarean delivery; 

Medicine Units Network; Ob HX= obstetric history; OR=odds ratio; PIH=pregnancy induced hypertension; PTD=permanentROC= receiver operating characteristic; TOL=trial of labor; UR= uterine rupture; VD=vaginal delivery; wks=weeks; wt=weig
Appendix P. Predictors of Uterine Rupture Table, continued 

References 

1. Shipp TD, Zelop C, Lieberman E. 

Assessment of the rate of uterine 

rupture at the first prenatal visit: a 

preliminary evaluation. J Matern 

Fetal Neonatal Med. 

2008;21(2):129-133. 

2. Macones GA, Cahill AG, Stamilio 

DM, Odibo A, Peipert J, Stevens EJ. 

Can uterine rupture in patients 

attempting vaginal birth after 

cesarean delivery be predicted?[see 

comment]. Am J Obstet Gynecol. 

2006;195(4):1148-1152. 

3. Smith GCS, White IR, Pell JP, 

Dobbie R. Predicting cesarean 

section and uterine rupture among 

women attempting vaginal birth after 

prior cesarean section.[see 

comment]. PLoS Med. 

2005;2(9):e252. 

4. Grobman WA, Lai Y, Landon MB, 

et al. Prediction of uterine rupture 

associated with attempted vaginal 

birth after cesarean delivery. Am J 

Obstet Gynecol. 2008;199(1):30.e31-

35. 

P-3 
Appendix Q. Detailed Transfusion/Hemorrhage Table 

Table Q-1. Transfusion rates for trial of labor versus elective repeat cesarean delivery among any gestational age s

Author, year 

Study 

description N Blood transfusion 

Blood Transfusion 

per 10,000 Hemorrhage 

Term gestational age Gregory, 20081 Retrospective 

cohort Low-risk = absence of maternal complications High-risk = any maternal condition ICD-9 codes 

41,450 Low-risk 

TOL: 38/8292 (0.46%) ERCD: 69/20,834 (0.33%) High-risk TOL: 25/3188 (0.78%) ERCD: 84/9136 (0.92%) 

Low-risk TOL: 46 ERCD: 33 High-risk TOL: 78 ERCD: 92 

Low-risk TOL: 196/8292 (2.36%) ERCD: 142/2083 (6.82%) High-risk TOL: 104/3188 (3.26%) ERCD: 144/9136 (1.57%) 

Loebel, 20042 Retrospective 

Cohort Community Teaching Hospital 

1,408 TOL: 927 ERCD: 481 

TOL: 12/927 (1.29%) ERCD: 3/481 (0.62%) 

TOL: 129 ERCD: 62 

Not reported 

Spong 20073 MFMU study TOL: 227/15,323 TOL: 148 Not reported 

19 Academic 39,117 (1.48%) ERCD: no labor: 92 centers ERCD: no labor: ERCD + labor: 165 

138/14,993 (0.92%) IRCD no labor: 214 ERCD + labor: 45/2721 (1.65%) IRCD no labor: 107/5002 (2.14%) IRCD + labor: 23/1078 (2.13%) 

IRCD + labor: 213 

Wen, 20044 Retrospective 

cohort Canadian Registry ICD-9 codes 

308,755 TOL: 245/128,960 

(0.19%) ERCD: 268/179,795 (0.15%), adjusted odds ratio 1.67 (1.39-2.00) 

TOL: 19 ERCD: 15 adjusted odds ratio 1.67 (1.39-2.00) 

Not reported 
Appendix Q. Detailed Transfusion/Hemorrhage Table, contin

Table Q-1. Transfusion rates for trial of labor versus elective repeat cesarean delivery among any gestational age s

Author, year 

Study 

description N Blood transfusion 

Blood Transfusion 

per 10,000 Hemorrhage 

Any gestational age Bais, 20015 Prospective 

Cohort Netherlands Regional hospital 

252 TOL: 8/184 (4.35%) 

ERCD: 4/68 (5.88%) 

TOL: 435 ERCD: 588 

Hemorrhage >500 mL TOL: 31/184 (16.85%) ERCD: 20/68 (29.41%) Hemorrhage >1000 mL TOL: 9/184 (4.89%) ERCD: 6/68 (8.83%) 

Flamm, 19946 Prospective 

cohort 10 Kaiser Hospital in CA 

7229 VBAC: 25/3516 

(0.71%) ERCD: 38/2208 (1.72%) (p=.0001) 

VBAC: 71 ERCD: 172  (p=.0001) 

Not reported 

Hibbard, 20017 Prospective 

Cohort University Hospital 

2450 ERCD: 6/431 (1.40%) 

TOL: 11/1,324 (0.83%) VBAC: 4/908 (0.44%) TOL-CD: 7/416 (1.68%) 

ERCD: 140 TOL: 83 VBAC: 44 TOL-CD: 168 

>1,000mL ERCD: 32/431 (7.42%) TOL: 46/1,324 (3.47%) VBAC: 7/908 (0.77%) TOL-CD: 39/416 (9.37%) >2,000mL ERCD: 5/431 (1.16%) TOL: 8/1,324 (0.60%) VBAC: 3/908 (0.33%) TOL-CD: 5/416 (1.20%) 

Kugler, 20088 Retrospective 

cohort Israel University Grand Multiparous women 

1102 ERCD: 18/328 (5.49%) 

TOL: 8/155 (5.16%) VBAC: 6/619 (1.0%) p<0.001 

ERCD: 549 TOL: 516 VBAC: 100 p<0.001 

ERCD: 3/328 (0.91%), TOL: 1/155 (0.64%), VBAC: 5/619 (0.81%) p <0.001 

Martin, 19839 Prospective 

Cohort 2 University Centers 

709 Not reported Not reported VBAC: 6/101 (5.94%) 

TOL-CD: 9/61 (14.75%) ERCD: 57/547 (10.42%) 
Appendix Q. Detailed Transfusion/Hemorrhage Table, contin

Table Q-1. Transfusion rates for trial of labor versus elective repeat cesarean delivery among any gestational age s

Author, year 

Study 

description N Blood transfusion 

Blood Transfusion 

per 10,000 Hemorrhage 

McMahon, 199610 Retrospective cohort 

Population based Longitudinal study Canada 

6,138 TOL: 36/3429 (1.05%) 

ERCD: 39/2889 (1.35%) 

TOL: 105 ERCD: 135 

Not reported 

Obara, 199711 Prospective 

Cohort University Hospital, Japan 

310 Not reported Not reported ERCD: 4/96 (4.17%) 

TOL: 3/214 (1.40%) 

Abbreviations: CA=California; ERCD=elective repeat cesarean delivery; IRCD=indicated repeat cesarean delivery; MFMU=

Medicine Units Network; mL=milliliter; TOL=trial of labor; TOL-CD=trial of labor followed by a cesarean delivery; VBAC=vag

cesarean 
Appendix Q. Detailed Transfusion/Hemorrhage Table, 

continued 

References 

1. Gregory KD, Korst LM, Fridman M, 

et al. Vaginal birth after cesarean: 

clinical risk factors associated with 

adverse outcome. Am J Obstet 

Gynecol. 2008;198(4):452.e451-410; 

discussion 452.e410-452. 

2. Loebel G, Zelop CM, Egan JFX, 

Wax J. Maternal and neonatal 

morbidity after elective repeat 

Cesarean delivery versus a trial of 

labor after previous Cesarean 

delivery in a community teaching 

hospital. J Matern Fetal Neonatal 

Med. 2004;15(4):243-246. 

3. Spong CY, Landon MB, Gilbert S, et 

al. Risk of uterine rupture and 

adverse perinatal outcome at term 

after cesarean delivery. Obstet 

Gynecol. 2007;110(4):801-807. 

4. Wen SW, Rusen ID, Walker M, et al. 

Comparison of maternal mortality 

and morbidity between trial of labor 

and elective cesarean section among 

women with previous cesarean 

delivery. Am J Obstet Gynecol. 

2004;191(4):1263-1269. 

5. Bais JM, van der Borden DM, Pel M, 

et al. Vaginal birth after caesarean 

section in a population with a low 

overall caesarean section rate. Eur J 

Obstet Gynecol Reprod Biol. 

2001;96(2):158-162. 

6. Flamm BL, Goings JR, Liu Y, 

Wolde-Tsadik G. Elective repeat 

cesarean delivery versus trial of 

labor: a prospective multicenter 

study. Obstet Gynecol. 

1994;83(6):927-932. 

7. Hibbard JU, Ismail MA, Wang Y, Te 

C, Karrison T. Failed vaginal birth 

after a cesarean section: how risky is 

it? I. Maternal morbidity. Am J 

Obstet Gynecol. 2001;184(7):1365-

1371; discussion 1371-1363. 

8. Kugler E, Shoham-Vardi I, Burstien 

E, Mazor M, Hershkovitz R. The 

safety of a trial of labor after 

cesarean section in a 

grandmultiparous population. Arch 

Gynecol Obstet. 2008;277(4):339-

344. 

9. Martin JN, Jr., Harris BA, Jr., 

Huddleston JF, et al. Vaginal 

delivery following previous cesarean 

birth. Am J Obstet Gynecol. 

1983;146(3):255-263. 

10. McMahon MJ, Luther ER, Bowes 

WA, Jr., Olshan AF. Comparison of 

a trial of labor with an elective 

second cesarean section.[see 

comment]. N Engl J Med. 

1996;335(10):689-695. 

11. Obara H, Minakami H, Koike T, 

Takamizawa S, Matsubara S, Sato I. 

Vaginal birth after cesarean delivery: 

results in 310 pregnancies. J Obstet 

Gynaecol Res. 1998;24(2):129-134. 

Q-4 

Q-4 
Appendix R. Detailed Infection Table 

Table R-1. Infection rates for trial of labor versus elective repeat cesarean delivery 

Endometritis or 

Author, year 

Study 

description N Fever 

Fever per 

10,000 

Endometritis 

Chorioamnionitis 

Chorioamnionitis per 

10,000 Wou

Term gestational age Eriksen, 19891 Retrospective cohort 

military base 

139 TOL: 4/71 

(5.6%) ERCD: 7/68 (10.2%) (p:NS) 

TOL: 560 ERCD: 1020 (p:NS) 

TOL: 2/71 (2.8%) ERCD: 1/68 (1.5%) (p:NS) 

TOL: 280 ERCD: 150 

Not repo

Hook, 19972 Prospective 

cohort level 1, 2, & 3 hospital included 

989 Maternal fever 

TOL: 38/492 (8%) ERCD: 0/497 (0%) (p=<0.0002) 

Maternal fever TOL: 80 ERCD: 0 (p=<0.0002) 

Not reported Not reported Not repo

Loebel,20043 Retrospective 

cohort community teaching hospital 

1,408 Not reported Not reported Not reported Not reported “Infectio

ERCD: 1(1.9%) VBAC 1TOL-CD (5.1%) (p:NS) 

Spong, 20074 MFMU 

network cohort 19 university hospitals 

39,117 Not reported Not reported TOL: 

442/15,323 (2.9%) ERCD no labor: 260/14,993(1.7 %) ERCD + labor: 101/2721 (3.7%) IRCD no labor 137/5002 (2.7%) IRCD + labor: 54/1078 (5.0%) 

TOL: 290 ERCD no labor: 170 ERCD + labor: 370 IRCD no labor 270 IRCD + labor: 500 

Not repo
Appendix R. Detailed Infection Table, continued 

Table R-1. Infection rates for trial of labor versus elective repeat cesarean delivery 

Endometritis or 

Author, year 

Study 

description N Fever 

Fever per 

10,000 

Endometritis 

Chorioamnionitis 

Chorioamnionitis per 

10,000 Wou

Wen, 20045 Retrospective 

cohort Canadian registry ICD-9 codes 

308,75 5 

Not reported Not reported Not reported Not reported “Postpa

InfectionTOL: 48(0.38%) ERCD: 8(0.47%)Adjusted 0.86 (0.77-0.9

All gestational ages Bais, 20016 Prospective 

cohort Netherlands regional hospital 

252 TOL: 16/184 

(9%) ERCD: 7/68 (10%) 

TOL: 900 ERCD: 1000 

Not reported Not reported Not repo

Cahill, 20067 Retrospective 

cohort 16 university & community hospitals 

6,619 TOL: 329/5041 

(6.52%) ERCD: 294/1578(18.63 %) 

TOL: 652 ERCD: 1863 

Not reported Not reported Not repo
Appendix R. Detailed Infection Table, continued 

Table R-1. Infection rates for trial of labor versus elective repeat cesarean delivery 

Endometritis or 

Author, year 

Study 

description N Fever 

Fever per 

10,000 

Endometritis 

Chorioamnionitis 

Chorioamnionitis per 

10,000 Wou

Durnwald, Retrospective 768 TOL: TOL: 520 Chorio- Chorio- Not repo

20048 cohort 

university hospital 

27/522(5.2%) VBAC: 7/344(2.0%) TOL-CD: 20/178 (11.2%) ERCD: 6/246 (2.4%) 

VBAC: 200 TOL-CD: 1120 ERCD: 240 

amnionitis TOL: 31/522(5.9%) VBAC: 18/344(5.2%) TOL-CD: 13/178(7.3%) ERCD: 0/246(0%) 

amnionitis TOL: 590 VBAC: 520 TOL-CD: 730 ERCD: 0 

Endometritis TOL: 24/522 (4.6%) VBAC: 7/344(2%) TOL-CD: 17/178(9.6%) ERCD: 5/246(2%) 

Endometritis TOL: 460 VBAC: 200 TOL-CD: 960 ERCD: 200 

Flamm, Prospective 7,229 TOL: 638/5022 TOL: 1270 Not reported Not reported Not repo

19949 cohort 

10 Kaiser hospital in California 

(12.7%) ERCD: 362/2208 (16.4%) 

ERCD: 1640 

McMahon, Retrospective 6,138 TOL: 171/3424 TOL: 530 Not reported Not reported Wound 199610 cohort 

population 

(5.3%) ERCD: 

ERCD: 640 TOL 43/

ERCD 6

based 185/2889 (6.4%) (2.2%) 

longitudinal study Canada 
Appendix R. Detailed Infection Table, continued 

Table R-1. Infection rates for trial of labor versus elective repeat cesarean delivery 

Endometritis or 

Author, year 

Study 

description N Fever 

Fever per 

10,000 

Endometritis 

Chorioamnionitis 

Chorioamnionitis per 

10,000 Wou

Phelan, 198711 Prospective Cohort 

University hospital >2 prior CD only 

2,643 Planned TOL 

159/ 1,796 (8.9%)* VBAC: 53/1465 (3.6%) TOL-CD: 106/331 (32%) No Planned TOL 163/847 (19.2%) VBAC: 4/69 (5.8%) ERCD: 56/314 (18%) IRCD: 103/464 (22%) 

Planned TOL 890* VBAC: 360 TOL-CD: 320 No Planned TOL 1920 VBAC: 580 ERCD: 1800 IRCD: 2200 

Not reported Not reported Not repo

Kugler, 200812 Retrospective cohort 

Israel University grand multiparous women 

1,102 IRCD† 10/328 

(3%), TOL: 9/619(1.5%), VBAC: 1/155(0.6%) 

IRCD† 300 

TOL: 150 VBAC: 60 

Amnionitis IRCDa 

4/328(1.2%) TOL: 5/619 (0.8%), VBAC: 14/155 (9.0%) 

Amnionitis IRCDa 120 

TOL: 80 VBAC: 900 

Not repo

Eglinton, 198413 Retrospective cohort 

university hospital 

871 VBAC: 

6/240(2.5%) TOL-CD: 27/136 (19.8%) ERCD: 176/495 (35.5%) 

VBAC: 250 TOL-CD: 1980 ERCD: 3550 

Not reported Not reported Not repo

Chauhan, 200114 

69 Not reported Not reported TOL: 9/30 

(30%) ERCD: 7/39 (18%) 

TOL: 300 ERCD: 1800 

Wound TOL: 8/3ERCD: 3
Appendix R. Detailed Infection Table, continued 

Table R-1. Infection rates for trial of labor versus elective repeat cesarean delivery 

Endometritis or 

Author, year 

Study 

description N Fever 

Fever per 

10,000 

Endometritis 

Chorioamnionitis 

Chorioamnionitis per 

10,000 Wou

Hibbard, Prospective 2,450 Not reported Not reported Endometritis Endometritis Not repo200115 cohort 

university 

ERCD: 38/431 (8.8%) 

ERCD: 880 TOL: 820 

hospital TOL: 108/1,324 VBAC: 340 

(8.2%) TOL-CD: 1850 VBAC: 31/908 Chorio-(3.4%) TOL-CD: 

amnionitis ERCD: 420 

77/416 (18.5%) TOL: 1280 Chorio- VBAC: 1120 amnionitis TOL-CD: 1600 ERCD: 18/431 (4.2%) TOL: 169/1,324 (12.8%) VBAC: 102/908 (11.2%) TOL-CD: 67/416 (16%) 
Appendix R. Detailed Infection Table, continued 

Table R-1. Infection rates for trial of labor versus elective repeat cesarean delivery 

Endometritis or 

Author, year 

Study 

description N Fever 

Fever per 

10,000 

Endometritis 

Chorioamnionitis 

Chorioamnionitis per 

10,000 Wou

Martin, Prospective 709 Not reported Not reported Endometritis Endometritis Wound 198316 cohort VBAC: VBAC: 100 VBAC: 0

2 university 1/101(1%) TOL-CD: 1150 TOL-CDcenters TOL-CD: 7/61 ERCD: 770 (4.9%) 

(11.5%) TOL: 490 ERCD: 1ERCD: 42/547 (2.2%) (7.7%) Any TOLTOL: 8/162 = (1.9%) 4.9% Pulmona

VBAC: 5TOL-CD(1.6%) ERCD: 3(5.7%) Other: VBAC: 3TOL-CD(3.2%) ERCD:3

*p < .05; † includes both ERCD as well as emergency CD 

Abbreviations: ERCD=elective repeat cesarean delivery; IRCD=indicated repeat cesarean delivery; NS=not significant; TO

CD=trial of labor followed by a cesarean delivery; UTI=urinary tract infection; VBAC=vaginal birth after cesarean 
Appendix R. Detailed Infection Table, continued 

References 

1. Eriksen NL, Buttino L, Jr. Vaginal 

birth after cesarean: a comparison of 

maternal and neonatal morbidity to 

elective repeat cesarean section. Am 

J Perinatol. 1989;6(4):375-379. 

2. Hook B, Kiwi R, Amini SB, 

Fanaroff A, Hack M. Neonatal 

morbidity after elective repeat 

cesarean section and trial of labor. 

Pediatrics. 1997;100(3 Pt 1):348-

353. 

3. Loebel G, Zelop CM, Egan JFX, 

Wax J. Maternal and neonatal 

morbidity after elective repeat 

Cesarean delivery versus a trial of 

labor after previous Cesarean 

delivery in a community teaching 

hospital. J Matern Fetal Neonatal 

Med. 2004;15(4):243-246. 

4. Spong CY, Landon MB, Gilbert S, et 

al. Risk of uterine rupture and 

adverse perinatal outcome at term 

after cesarean delivery. Obstet 

Gynecol. 2007;110(4):801-807. 

5. Wen SW, Rusen ID, Walker M, et al. 

Comparison of maternal mortality 

and morbidity between trial of labor 

and elective cesarean section among 

women with previous cesarean 

delivery. Am J Obstet Gynecol. 

2004;191(4):1263-1269. 

6. Bais JM, van der Borden DM, Pel M, 

et al. Vaginal birth after caesarean 

section in a population with a low 

overall caesarean section rate. Eur J 

Obstet Gynecol Reprod Biol. 

2001;96(2):158-162. 

7. Cahill AG, Stamilio DM, Odibo AO, 

et al. Is vaginal birth after cesarean 

(VBAC) or elective repeat cesarean 

safer in women with a prior vaginal 

delivery? Am J Obstet Gynecol. 

2006;195(4):1143-1147. 

8. Durnwald C, Mercer B. Vaginal 

birth after Cesarean delivery: 

predicting success, risks of failure. J 

Matern Fetal Neonatal Med. 

2004;15(6):388-393. 

9. Flamm BL, Goings JR, Liu Y, 

Wolde-Tsadik G. Elective repeat 

cesarean delivery versus trial of 

labor: a prospective multicenter 

study. Obstet Gynecol. 

1994;83(6):927-932. 

10. McMahon MJ, Luther ER, Bowes 

WA, Jr., Olshan AF. Comparison of 

a trial of labor with an elective 

second cesarean section.[see 

comment]. N Engl J Med. 

1996;335(10):689-695. 

11. Phelan JP, Clark SL, Diaz F, Paul 

RH. Vaginal birth after cesarean. Am 

J Obstet Gynecol. 1987;157(6):1510-

1515. 

12. Kugler E, Shoham-Vardi I, Burstien 

E, Mazor M, Hershkovitz R. The 

safety of a trial of labor after 

cesarean section in a 

grandmultiparous population. Arch 

Gynecol Obstet. 2008;277(4):339-

344. 

13. Eglinton GS, Phelan JP, Yeh S, Diaz 

FP, Wallace TM, Paul RH. Outcome 

of a trial of labor after prior cesarean 

delivery. J Reprod Med. 

1984;29(1):3-8. 

14. Chauhan SP, Magann EF, Carroll 

CS, Barrilleaux PS, Scardo JA, 

Martin JN, Jr. Mode of delivery for 

the morbidly obese with prior 

cesarean delivery: vaginal versus 

repeat cesarean section. Am J Obstet 

Gynecol. 2001;185(2):349-354. 

R-7 
Appendix R. Detailed Infection Table, continued 

15. Hibbard JU, Ismail MA, Wang Y, Te 

C, Karrison T. Failed vaginal birth 

after a cesarean section: how risky is 

it? I. Maternal morbidity. Am J 

Obstet Gynecol. 2001;184(7):1365-

1371; discussion 1371-1363. 

16. Martin JN, Jr., Harris BA, Jr., 

Huddleston JF, et al. Vaginal 

delivery following previous cesarean 

birth. Am J Obstet Gynecol. 

1983;146(3):255-263. 

R-8 
 

 

 

 

 

Appendix S. Detailed Hospital Stay Table 

Table S-1. Length of stay: all studies from the United States 

Author, year 

Study 

description N Length of stay (days) 

Term gestational age 

Gregory, 20081 Retrospective 

cohort 

-Low risk: 

absence of 

maternal 

complications 

-High Risk: any 

maternal 

condition 

ICD-9 codes 

41,450 Low-risk-TOL: 2.25 

High-risk 

TOL: 2.86 

Low-risk 

ERCD: 3.02 

High-risk 

ERCD: 3.26 

Loebel, 20042 Retrospective 

cohort 

community 

teaching hospital 

1,408 TOL: 2.02 ERCD: 3.14 

Hook, 19973 Prospective 

cohort 

level 1, 2, & 3 

hospitals 

included 

989 TOL only: 3.6(+1) 

VBAC: 3.1; (+2) 

TOL-CD: 4.8; (+2)* 

ERCD: 4.5(+1)† 

Any gestational age 

Eglinton, 19844

 Retrospective 

cohort 

university 

hospital 

871 VBAC 2.4(1.0) 

TOL-CD 5(1.4) 

ERCD-VD :2.3 (0.7) 

ERCD no labor:4.9 (1.6) 

ERCD labor:4.9 (1.5) 

Eriksen, 19895 Retrospective 

cohort 

military base 

139 TOL: 3.1 + 1.6 ERCD: 5.4 days + 2.0‡ 

Flamm, 19946 Prospective 

cohort 

10 Kaiser 

hospitals in 

California 

7,229 TOL: 57.2 hours + 31.1 ERCD: 84.9 hours 

+26.3§ 

Hibbard, 20017 Prospective 

cohort 

university 

hospital 

2,450 TOL: 3.26 ± 2.61 

VBAC: 2.34 ± 1.85 

TOL-CD: 5.31 ± 2.88 

ERCD: 5.04 ± 3.09 

Phelan, 19878

 Prospective 

cohort 

university 

hospital 

>2 prior CD only 

2,643 VBAC: 2.2 

TOL-CD: 4.2 

ERCD: 4.2 

* p <0.01

†

 p =0.002

‡ p=0.001 

§

 p<0.001 

Abbreviations: CD=cesarean delivery; ERCD=elective repeat cesarean delivery; TOL=trial of labor; TOLCD=trial of labor followed by a cesarean delivery; VBAC=vaginal birth after a cesarean 

S-1 
Appendix S. Detailed Hospital Stay Table, continued 

References 

1. Gregory KD, Korst LM, Fridman M, 

et al. Vaginal birth after cesarean: 

clinical risk factors associated with 

adverse outcome. Am J Obstet 

Gynecol. 2008;198(4):452.e451-410; 

discussion 452.e410-452. 

2. Loebel G, Zelop CM, Egan JFX, 

Wax J. Maternal and neonatal 

morbidity after elective repeat 

Cesarean delivery versus a trial of 

labor after previous Cesarean 

delivery in a community teaching 

hospital. J Matern Fetal Neonatal 

Med. 2004;15(4):243-246. 

3. Hook B, Kiwi R, Amini SB, 

Fanaroff A, Hack M. Neonatal 

morbidity after elective repeat 

cesarean section and trial of labor. 

Pediatrics. 1997;100(3 Pt 1):348-

353. 

4. Eglinton GS, Phelan JP, Yeh S, Diaz 

FP, Wallace TM, Paul RH. Outcome 

of a trial of labor after prior cesarean 

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