Diagnosis of Obstetric Anal Sphincter Injuries (OASIs) Using Transperineal Ultrasound Scan (TPUS)
Conditions: Obstetric Anal Sphincter Injury
Sponsor: Lewisham and Greenwich NHS Trust

 
1
STUDY PROTOCOL 
 
TITLE OF THE STUDY 
Diagnosis of Obstetric Anal Sphincter Injuries (OASIs) using Transperineal 
Ultrasound Scan (TPUS) 
 
 
PROTOCOL VERSION NUMBER: 
Version 2 
 
RESEARCH REFERENCE NUMBER: 
IRAS number 196995 
 
DOCUMENT DATE: 
21st December 2016 
 
 
 
 
 
 
 
 
 
 

 
2
 
 
 
KEY STUDY CONTACTS 
Research fellow 
Ka Woon Wong 
ST5 in Obstetric and Gynaecology,  
University Hospital Lewisham  
Mobile: 07789317707 
E-mail: Kandice.wong@doctors.org.uk 
 
Chief investigator 
Mr. Vasanth Andrews 
Consultant Obstetrician and Gynaecologist, 
University Hospital Lewisham 
 
Supervisors: 
Mr. Vasanth Andrews 
Consultant Obstetrician and Gynaecologist, 
University Hospital Lewisham 
 
Miss Ranee Thakar 
Consultant Obstetrician and Urogynaecologist, 
Croydon University Hospital 
 
Mr. Abdul H Sultan 
Consultant Obstetrician and Gynaecologist, 
Croydon University Hospital 

 
3
 
Miss Heather Allen Coward 
Consultant Obstetrician and Gynaecologist, 
Croydon University Hospital 
 
 
 
 
 
 
 
STUDY SUMMARY 
Study Title 
Diagnosis of Obstetric Anal Sphincter Injuries (OASIs) 
using Transperineal Ultrasound Scan (TPUS) 
 
Study Design 
Prospective observational study 
Study Participants 
Women who undergoing their first vaginal delivery 
Planned Size of Sample (if 
applicable) 
216 
Planned Study Period 
January 2017 to April 2018 
Research Question/Aim(s) 
 
1) HYPOTHESIS  
- 
Transperineal 
Ultrasound 
Scan 
(TPUS) 
at 
delivery will increase the detection of Obstetric 
Anal Sphincter Injuries (OASIs). 

 
4
 
2) PRIMARY AIM 
- 
To 
determine 
whether 
the 
use 
of 
the 
transperineal 
ultrasound 
will 
improve 
the 
detection of OASIs immediately following vaginal 
delivery. 
 
3) SECONDARY AIMS 
- 
To measure hiatal dimensions during labour and 
correlate to levator detachments. 
- 
To correlate intrapartum fetal head position and 
station identified using three-dimensional (3D) 
transperineal and transabdominal ultrasound with 
levator injury. 
- 
To assess anal sphincter integrity immediately 
after primary repair of OASIs with transperineal 
ultrasound. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
5
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
LIST of CONTENTS 
GENERAL INFORMATION 
 
TITLE PAGE  
1 
KEY STUDY CONTACTS  
2 
STUDY SUMMARY  
3,4 
LIST of CONTENTS 
 
5 
STUDY FLOW CHART 
 
6 
SECTION  
1. BACKGROUND  
7-12 
2. RESEARCH QUESTION/AIM(S)  
13 
3. DESIGN AND METHODOLOGY 
14-16 
4. ETHICAL AND REGULATORY COMPLIANCE 
17-18 
5. REFERENCES 
19- 23 
 

 
6
 
 
 
 
 
 
 
 
 
STUDY PROTOCOL 
 
BACKGROUND  
 
Obstetric Anal Sphincter Injuries (OASIs) 
 
The incidence of anal incontinence - “the involuntary loss of flatus, liquid or stool that 
is a social or hygienic problem” (1)  is reported to occur in 20-68 % of women after 
Obstetric Anal Sphincter Injuries (OASIs) (2) (3) (4). Obstetric related anal 
incontinence was previously believed to be due to pudendal neuropathy (5) (6) (7). 
However with the advent of Endoanal Ultrasound Scan (EAUS) it has become 
apparent that mechanical trauma to the anal sphincter is the major aetiological factor. 
 
Three dimensional (3D) EAUS is the gold standard tool to detect OASIs (8). It is 
however not available in most obstetric units. A potential alternative imaging modality 
is Transperineal Ultrasound Scan (TPUS) (9) (10) (11) (12) (13). TPUS is readily 

 
7
available in all obstetric units and therefore potentially can be used as a diagnostic 
tool to detect OASIs. In addition, it allows assessment of the levator ani muscle 
(LAM), which is believed to play an important role in the maintenance of anal 
incontinence (14). 
 
Comparative studies have been done between TPUS and EAUS and have shown a 
moderate to good correlation between the two imaging modalities for the evaluation 
of the anal sphincter complex (15) (16). Roos et al (17) compared TPUS with EAUS 
on women who had an OASIs or symptoms of anal incontinence without OASIs over 
12 months following delivery. They found that TPUS is good at detecting normal anal 
sphincters. However, when an anal sphincter defect is detected with TPUS it 
requires further clinical assessment to determine whether an OASIs has actually 
occurred. The authors therefore recommended that if TPUS reveals an intact anal 
sphincter then no further test is necessary; however if TPUS reveals a defect, a 
clinical examination and EAUS should be performed to confirm damage to the anal 
sphincter.   In a study by Oom et al (15), TPUS was able to detect 70% of cases with 
external anal sphincter (EAS) defects and all cases of internal anal sphincter  (IAS) 
defects identified on EAUS. Roche et al (18) scanned 20 primiparous women found  
and found that two dimensional (2D) TPUS detected all defects identified using 2D 
EAUS. Ros et al (19) also demonstrated a good correlation with 3D EAUS when 3D 
TPUS is used to detect residual anal sphincter defects 3 months to 6 years after 
primary repair of OASIs. 
 
 

 
8
It is known that OASIs can lead to anal incontinence especially when damage to the 
anal sphincter is not recognised at the time of delivery (20) (21). The incidence of 
clinically undetected OASIs has been shown to vary between 13 to 87% (11) (22) 
(23). Two clinical studies have demonstrated that when a trained doctor re-examined 
the perineum and anal sphincter that the rate of OASIs doubled (22) (24). This 
highlights the need to improve education of obstetricians and midwives in perineal 
anatomy and clinical diagnosis of OASIs. However despite training, doctors and 
midwives still fail to identify all OASIs (11) (25). Although It has been shown  that 
EAUS can increase the detection rate of OASIs (22),  it is not widely available in 
most UK obstetric units. In contrast, TPUS is available in most obstetric units and we 
therefore wish to determine whether TPUS in addition to a routine clinical 
examination will increase the detection rate of OASIs. 
 
Anal incontinence can occur if OASIs are not repaired adequately (26) (27) (28). 
There is a significant correlation between the extent of an anal sphincter defect and 
the degree of anal incontinence (29). Ultrasound assessment between one week and 
one year after primary repair of OASIs has shown that  between 16 to 90% (12) (28) 
(26) (15) (27) (30) have  a residual anal sphincter defect. Women with a residual 
anal sphincter defect have significantly more symptoms of anal incontinence than 
those without a demonstrable defect (26). It is therefore not unreasonable to assume 
that some of these residual defects on scans represent injuries that were either not 
or incompletely repaired at the time of delivery. We therefore wish to investigate 
whether the use of TPUS immediately after primary repair of OASIs may be able to 
detect an inadequate repair which will be confirmed at the six to eight weeks follow-
up. 

 
9
 
 
The reported rates of anal incontinence following primary repair of OASIs range 
between 15 and 61% (31). Women with anal incontinence are more likely to have an  
EAS defect (26).  We wish to perform a TPUS at six to eight weeks postpartum to 
assess the anal sphincter, and determine whether there are differences in the 
morphology compared to TPUS findings at delivery.   
 
 
Hiatal dimension and levator ani avulsion 
The incidence of levator ani muscle (LAM) avulsion is between 10 and 35% (32) (33) 
(34) (35) and can occur in up to 28% (33) of women undergoing their first vaginal 
delivery (32) (33). LAM avulsion can have a significant impact on faecal (13) (36) 
(37) (38) and urinary incontinence (39) (32) (40) (41) (42) (43) and sexual function 
(44) and is a major contributing factor to the development of pelvic organ prolapse 
(45) (46) (47) (34).  Repairing LAM avulsion has been proven to be unsuccessful  
(48) (49). There have been attempts to try and find ways to prevent pelvic floor 
damage during vaginal delivery e.g EPI-NO ® (Tecsana GMBH, Muenchen, 
Germany).   It is a mechanical device which is inserted into the vagina antenatally 
and stretches the vagina and perineum. However a recent randomized controlled 
trial  has shown it to be of no benefit (50).  Given that surgical repair and mechanical 
devices have been unsuccessful, research needs to focus on a better understanding 
of when these injuries occur in labour, with a view to preventing them happening in 
the first place.   
 

 
10
A computerised model has demonstrated that the pelvic floor muscles undergo 
extensive stretching during a vaginal delivery (51). Several forms of injury have been 
described including avulsions, traumatic over-distension and hematomas (39) (52) 
(53). LAM avulsion have been investigated in labour and seem to only occur at 
delivery and not during the first and second stages of labour (54).  However it is also 
known that smaller hiatal dimensions during the third trimester are found to be 
associated with a higher intervention rate for both instrumental deliveries and 
caesarean sections (55). Given that smaller hiatal dimensions in the third trimester 
lead to more obstetric intervention, it may be that particular dimensions or changes 
to these muscles in labour have an impact on the mode of delivery. Therefore 
performing TPUS in labour will give us a better understanding of the changes that 
occur in normal labour, and this may prove to be useful in prediction of mode of 
delivery.    
 
Computerised models suggest that with the descent of the fetal head that there is 
distension of the pelvic floor muscles (51). The descent of the fetal head is usually 
determined by digital vaginal examination (DVE) in relation to the ischial spines and 
is called the fetal head station (56).  This is however a subjective measure but can 
be measured objectively with TPUS (57) (58) (59) (58) (60).  Therefore we wish to 
investigate changes to the pelvic floor muscles in relation to fetal head station 
objectively using TPUS.  
 
Forceps delivery (61) (62) (63) (41) (64) (65) (45), prolonged second stage (66) (62) 
(67) and occipito-posterior (OP) position (33) are risk factors for LAM avulsion. The 
study evaluating OP with LAM avulsion were done as the baby was being delivered 

 
11
when one can see the position of the baby’s head (33).  In labour the diagnosis of 
OP position was made by a DVE.  However there is good evidence that diagnosing 
the position of the head by DVE can be difficult (68) and that ultrasound diagnosis is 
more accurate (69) (70) (71). Given that there have been no studies evaluating the 
position of the fetal head in labour and its relation to LAM avulsion, we propose to 
accurately diagnose fetal head position in labour and correlate it with LAM avulsion 
using TPUS. 
 
In summary LAM avulsion and hiatal dimensions are associated with pelvic organ 
prolapse (45) (46) (47) (34) and both anal (13) (36) (37) (38) and urinary 
incontinence (39) (32) (40) (41) (42) (43).  TPUS can be used to evaluate changes to 
these muscles in labour and also objectively measure fetal head station and position.  
This will be the first to study to evaluate these changes during normal labour.  
Understanding this is important so that preventative strategies can be developed to 
try and improve the quality of life for women.     
 
 
 
 
 
 
 
 
 
 

 
12
 
 
 
HYPOTHESIS  
- 
Transperineal ultrasound at delivery will increase the detection of OASIs. 
 
AIMS OF THE STUDY 
 
Primary Aim 
 
- 
To determine whether the use of the transperineal ultrasound will improve the 
detection of OASIs immediately after vaginal delivery. 
 
Secondary Aims 
 
- 
To measure hiatal dimensions during labour and correlate to levator 
detachments. 
- 
To correlate intrapartum fetal head position and station identified using three-
dimensional (3D) transperineal and transabdominal ultrasound with levator 
injury. 
- 
To assess anal sphincter integrity immediately after primary repair of OASIs 
with transperineal ultrasound. 
 
 
 
 

 
13
 
 
 
 
DESIGN AND METHODOLOGY 
 
Prospective study to be conducted between January 2017 and April 2018 at 
University Hospital Lewisham.  Recruitment will start in January 2017 and stop in 
April 2018.  
 
Sample identification 
All women attending the hospital for routine anomaly ultrasound examinations 
between 20 and 22 weeks of gestation will be invited to participate and will be given 
an information leaflet at that stage. The initial approach will be made by a member of 
the clinical care team when women are admitted for induction of labour or are in 
labour on the delivery suite and the research team can then approach if the potential 
participant agrees to be approached. The research fellow (KW) will invite eligible 
women to participate in the study. The source of identifiable personal information 
that will be used to identify potential participants will be their maternity notes.   
 
 
Patients inclusion criteria  
 
The inclusion criteria are: 
- 
women who are undergoing their first vaginal delivery 
- 
37 weeks of gestation or more 
- 
a singleton pregnancy 

 
14
- 
cephalic presentation 
- 
maternal age 18 years old or more and being able to read and understand 
English.  
 
 
Patients exclusion criteria 
 
Exclusion criteria are those who do not fit in the inclusion criteria.  
 
Size of sample 
Power calculation: The incidence of clinically identified OASIS in nulliparous women 
is 6%. With increased surveillance with transeperineal ultraousnd and a detailed 
examination by a trained doctor we predict the detection rate of OASIS will be 12%.  
Assuming that 10% of the subjects will have discordant responses, and also 
assuming a 5% significance level and 80% power, it is calculated that 216 women 
would be required for the study.  
Statistics 
Due to the paired binary nature of the data (i.e. two measurements for each subject), 
the McNemar test will be used for the data analysis. 
 
Method of evaluation 
The research fellow (KW) will assess fetal head station and hiatal dimensions by TPUS 
and fetal head position by transabdominal ultrasound.  
 

 
15
Perineal and anal sphincter trauma will be assessed and classified by the accoucher 
following vaginal delivery. Women will be re-examined by the research doctor (KW) 
who is trained in performing a detailed vaginal, perineal and rectal examination. When 
an OASIs is identified by the research fellow that is missed by the accoucher it will be 
verified by the consultant between 08.00 and 20.30 and by the ST6-7, specialty doctor 
or consultant out of hours and repaired. 
 
Secondly TPUS will be performed to assess anal sphincter and hiatal dimension in the 
immediate postpartum period on all women in the study.  TPUS will be repeated after 
the primary repair of OASIs to check the integrity of the anal sphincter. Images will be 
stored for independent assessment by experts in TPUS.  
 
A follow-up appointment will be arranged for six to eight weeks later. At follow-up, all 
patients will be asked to complete a standardised questionnaire including symptoms 
of anal incontinence according to the St. Mark’s Incontinence Score (SMIS) and 
undergo a repeat TPUS to assess the anal sphincter and hiatal dimensions.  
 
 
Demographic and obstetric data will be collected prospectively from the maternity 
notes, including: maternal age, gestational age at delivery, parity, body mass index, 
history of previous caesarean section, spontaneous or induced labour, duration of 
first and second stage of labour, indication for operative vaginal delivery, final mode 
of delivery, mediolateral episiotomy, and neonatal weight. The following 
ultrasonographic data will also collected: fetal head position, angle of progression, 
hiatal dimension, signs of levator avulsion, anal sphincter integrity. 

 
16
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
ETHICAL CONSIDERATION 
This study is a self-funded project.  Information about the study will be given to 
women during the antenatal period.  Those who agree to participate will be 
consented on admission to labour ward.  
 
CONSENT 
Informed consent will be obtained prior to participating. A discussion will be carried 
out between the potential participants and the research fellow (KW) about the nature 
and objectives of the study and possible risks associated with their participation. An 

 
17
opportunity will be given to potential participants to ask questions. Written material 
(e.g. information leaflet and consent document) will be given.  
 
REGULATORY COMPLIANCE  
 
Before enrolling patients into the study, the chief investigator (KW) will apply for NHS 
permission from the NHS Research & Development (R&D). If there are any 
amendments that will potentially affect a site’s NHS permission, the chief investigator 
will confirm with R&D department that NHS permission is on going. 
 
PROTOCOL COMPLIANCE 
Any accidental protocol deviations will be documented on the relevant forms and 
reported to the chief investigator. 
 
DATA PROTECTION AND PATIENT CONFIDENTIALITY 
All investigators will comply with the requirements of the Data Protection Act 1998 
with regards to the collection, storage, processing and disclosure of personal 
information and will uphold the Act’s core principles.  
 
 

 
18
STUDY FLOW CHART 
 
 

 
19
 
Bibliography 
1. Norton C, Christiansen J, Butler U, Harari D, Nelson RL, Pemberton J, Price K, Rovnor E, 
Sultan A. Anal Incontinence. In Abrams P CLKWA. Incontinence. 2nd ed. Plymouth: 
Health Publication Ltd; 2002. p. 985-1044. 
2. Abramowitz L, Sobhani I, Ganansia R, Vuagnat A, Benifla JL, Darai E, Madelenat P, 
Mignon M. Are sphincter defects the cause of anal incontinence after vaginal delivery? 
Results of a prospective study. Dis Colon Rectum. 2000; 43: p. 590-598. 
3. Sultan AH, Kamm MA, Hudson CN, Thomas JM, Bartram CI. Anal sphincter disruption 
during vaginal delivery. N Engl J Med. 1993; 329: p. 1905–1911. 
4. Oberwalder M, Connor J, Wexner SD. Meta-analysis to determine the incidence of 
obstetric anal sphincter damage. Br J Surg. 2003; 90: p. 1333–1337. 
5. Snooks SJ, Swash M, Setchell M, Henry MM.. Injury to innervation of pelvic floor 
sphincter musculature in childbirth. Lancet 2. 1984;: p. 546-550. 
6. Snooks SJ, Swash M, Mathers SE, Henry MM.. Effect of vaginal delivery on the pelvic 
floor: a 5-year follow-up. Br J Surg 77. 1990;: p. 1358-1360. 
7. Allen RE, Hosker GL, Smith ARB, Warrell DW.. Pelvic floor damage in childbirth - a 
neurophysiological study. BJOG. 1990; 97: p. 770-779.. 
8. Gold DM, Bartram CI, Halligan S. Three-dimensional endoanal sonography in assessing 
anal canal injury. Br J Surg. 1999; 86: p. 365. 
9. Kleinübing H Jr JJMOBSPT. Transperineal ultrasonography: new method to image the 
anorectal region. Dis Colon Rectum. 2000 Nov; 43(11): p. 1572-4. 
10. Peschers UM, DeLancey JO, Schaer GN, Schuessler B. Exoanal Ultrasound of the anal 
shpincter: normal anatomy and sphincter defects. Br J Obstet Gynaecol. 1997; 104: p. 
999-1003. 
11. Guzman-Rojas R.A., Shek K. L., Langer S.M. and Dietz H. P.. Prevalence of anal sphincter 
injury in primiparous women. Ultrasound Obstet Gynecol. 2013; 42: p. 461-466. 
12. Valsky DV, Cohen SM, Lipschuetz M, Hochner-Celnikier D, Yagel S. Three Dimensional 
transperineal ultrasound findings associated with anal incontinence after intrapartum 
sphincter tears in primparous women. Ultrasound Obstet Gynecol. 2012; 39: p. 83-90. 
13. Weinstein MM, Pretorius DH, Jung SA, Nager CW, Mittal RK. Transperineal 3-
dimensional ultrasound imaging for detection of anatomical defects in the anal 
sphincter complex muscles. Clin Gastroenterol Hepatol. 2009; 7: p. 205-11. 
14. Liu J, Guaderrama N, Nager CW, Pretorius DH, Master S, Mittal RK. Functional correlates 
of anal canal anatomy: puborectalis muscle and anal canal pressure. Am J Gastroenterol. 
2006; 101: p. 1092-1097. 
15. Oom DM, West RL, Schouten WR, Steensma AB. Detection of anal sphincter defects in 
female patients with fecal incontinence: a comparison of 3-dimensional transperineal 
ultrasound and 2-dimensional endoanal ultrasound. Dis Colon Rectum. 2012 Jun; 55(6): 
p. 646-52. 
16. Lohse C, Bretones S, Boulvain M,Weil A, Krauer F. Transperineal versus endo-anal 

 
20
ultrasound in the detection of anal sphincter tears. Eur J Obstet Gynecol. 2002; 103: p. 
79-82. 
17. Roos AM, Abdool Z, Sultan AH, Thakar R. The diagnostic accuracy of endovaginal and 
transperineal ultrasound for detecting anal sphincter defects: The PREDICT study. Clin 
Radiol. 2011 July; 66(7): p. 597-604. 
18. Roche B, Deléaval J, Fransioli A, Marti MC. Comparison of transanal and external 
perineal ultrasonography. Eur Radiol. 2001; 11(7): p. 1165-70. 
19. Ros C, Martínez-Franco E, Wozniak MM, Cassado J, Santoro GA, Elías N, López M, Palacio 
M, Wieczorek AP, Espuña-Pons M. Postpartum 2D and 3D ultrasound evaluation of the 
anal sphincter complex in women with obstetric anal sphincter injuries. Ultrasound 
Obstet Gynecol. Epub. 2016 March 22. 
20. Fynes M, Donnelly V, Behan M, O’Connell P, O’Herlihy C.. Effect of second vaginal 
delivery on anorectal physiology and faecal continence: a prospective study. Lancet. 
1999; 354: p. 983-986. 
21. Maslovitz S, Jaffa A, Levin I, Almog B, Lessing JB, Wolman I. The clinical significance of 
postpartum transperineal ultrasound of the anal sphincter. Eur J Obstet Gynecol Reprod 
Biol. 2007 September; 134(1): p. 115-9. 
22. Andrews A, Sultan A, Thakar R, Jones P. Occult anal shpincter injuries - myth or reality? 
BJOG. 2006; 113: p. 195-200. 
23. Faltin DL, Boulvain M, Irion O, Bretones S, Stan C, Weil A. Diagnosis of anal sphincter 
tears by postpartum endosonography to predict fecal incontinence. Obstet Gynecol. 
2000 May; 95(5): p. 643-7. 
24. Groom KM1, Paterson-Brown S. Can we improve on the diagnosis of third degree tears? 
Eur J Obstet Gynecol Reprod Biol. 2002 Feb 10;101(1):19-21. 2002 Feb; 101(1): p. 19-21. 
25. Ozyurt, S. Aksoy, H. Ali Gedikbasi, A. Yildirim, G. Screening occult anal sphincter injuries 
in primigravid women after vaginal delivery with transperineal use of vaginal probe: a 
prospective, randomized controlled trial. Arch Gynecol Obstet. 2015; 292: p. 853-859. 
26. Shek KL, Guzman-Rojas R, Dietz HP. Residual defects of the external anal sphincter 
following primary repair: an observational study using transperineal ultrasound. 
Ultrasound Obstet Gynecol. 2014 Dec; 44(6): p. 704-9. 
27. Norderval S, Markskog A, Rossaak K, Voven B. Correlation between anal shpincter 
defects and anal incontinence following obstetric sphincter tears: assessment using 
scoring systems for sonographic classification of defects. Ultrasound Obstet Gynecol. 
2008; 31: p. 78-84. 
28. Starck M, Bohe M, Valentin L. The extent of endosonographic anal sphincter defects 
after primary repair of obstetric sphincter tears increases over time and is related to 
anal incontinence. Ultrasound obstet Gynecol. 2006; 27: p. 188-197. 
29. Norderval S, Markskog A, RØssaak K, Vonen B. Correlation between anal sphincter 
defects and anal incontinence following obstetric sphincter tears: assessment using 
scoring systems for sonographic classification of defects. Ultrasound Obstet Gynecol. 
2008; 31: p. 78-84. 
30. Roos AM, Thakar R, Sultan AH. Outcome of primary repair of obstetric anal sphincter 
injuries (OASIS): does the grade of tear matter? Ultrasound Obstet Gynecol. 2010; 36: p. 
368–374. 

 
21
31. Sultan AH, Kettle C. Diagnosis of perineal trauma. In Sultan AH TRFD, editor. Perineal 
and anal sphincter trauma. 1st ed. London: Springer-Lerlag; 2009. p. 13-9. 
32. Dietz HP, Lanzarone V. Levator trauma after vaginal delivery. Obstet Gynecol. 2005; 106: 
p. 707-12. 
33. Shek K, Dietz H.. Intrapartum risk factors for levator trauma. BJOG. 2010; 117: p. 1485-
1492. 
34. Shek KL, Dietz HP. Can levator avulsion be predicted antenatally? Am J Obstet Gynecol. 
2010; 202(586): p. e1-6. 
35. Kearney R, Miller J, Ashton-Miller J, DeLancey J. Obstetrics factors associated with 
levator ani injury after childbirth. 2006;107:144–9. Obstet Gynecol. 2006; 107: p. 144-9. 
36. Heilbrun ME, Nygaard IE, Lockhart ME, Richter HE, Brown MB, Kenton KS, et al. 
Correlation between levatorani muscle injuries on magnetic resonance imaging and 
fecal incontinence, pelvic organ prolapse, and urinary incontinence in primiparous 
women. Am J Obstet Gynecol. 2010; 202: p. 488 e1-6. 
37. Lewicky-Gaupp C, Brincat C, Yousuf A, Patel AD, DeLancey JO, Fenner DE. Fecal 
incontinence in older women: are levatorani defects a factor? Am J Obstet Gynecol. 
2010; 202: p. 491 e1 - e6. 
38. Chantarasorn V, Shek KL, Dietz HP. Sonographic detection of puborectalis muscle 
avulsion is not associated with anal incontinence. Aust N Z J Obstet Gynaecol. 2011; 51: 
p. 130-5. 
39. DeLancey JO, Kearney R, Chou Q, Speights S, Binno S. The appearance of levator ani 
muscle abnormalities in magnetic resonance images after vaginal delivery. Obstet 
Gynecol. 2003; 191: p. 46-53. 
40. Dietz HP, Kirby A, Shek LK, Bedwell PJ. Does avulsion of the puborectalis muscle affect 
bladder function? Int Urogynecol J. 2009; 20: p. 967-72. 
41. Dietz HP, Kirby A. Modelling the likelihood of levator avulsion in a urogynaecological 
population. Aust N Z J Obstet Gynaecol. 2010; 50: p. 268-72. 
42. Morgan DM, Cardoza P, Guire K, Fenner DE, DeLancey JOL. Levator ani defect status and 
lower urinary tract symptoms in women with pelvic organ prolapse. Int Urogynecol J. 
2010; 21: p. 47-52. 
43. Kamisan Atan I; Gerges, B; Shek, SL; Dietz, HP. The association between vaginal parity 
and hiatal dimensions: a retrospective observational study in a tertiary 
urogynaecological centre. 2015; 122(6): p. 867-72. 
44. van Delft, K; Thakar, R; Sultan, AH; Kluivers, KB. Does the prevalence of levator ani 
muscle avulsion differ when assessed using tomographic ultrasound imaging at rest vs 
on maximum pelvic floor muscle contraction? Ultrasound Obstet Gynecol. 2015 Jul; 
46(1): p. 99-103. 
45. DeLancey JO, Morgan DM, Fenner DE, Kearney R, Guire K, Miller JM, et al. Comparison 
of levator ani muscle defects and function in women with and without pelvic organ 
prolapse. Obstet Gynecol. 2007; 109: p. 295-302. 
46. Dietz HP, Simpson JM. Levator trauma is associated with pelvic organ prolapse. BJOG 
2008. 2008; 115: p. 979-84. 
47. Durnea CM, O'Reilly BA, Khashan AS, Kenny LC, Durnea UA, Smyth MM, Dietz HP. Status 
of the pelvic floor in young primiparous women. Ultrasound Obstet Gynecol. 2015 

 
22
September; 46(3): p. 356-62. 
48. Dietz H, Gillespie A, Phadke P.. Avulsion of the pubovisceral muscle associated with large 
vaginal tear after normal vaginal delivery at term.. Aust NZ J Obstet Gynaecol. 2007; 47: 
p. 341-344. 
49. Shobeiri SA1, Chimpiri AR, Allen A, Nihira MA, Quiroz LH. Surgical reconstitution of a 
unilaterally avulsed symptomatic puborectalis muscle using autologous fascia lata. 
Obstet Gynecol. 2009; 114: 480–482.: p. 480-482. 
50. Kamisan Atan I1,2, Shek KL1,3, Langer S, Guzman Rojas R, Caudwell-Hall J, Daly JO, Dietz 
HP. Does the EPI-NO prevent levator trauma? A randomised controlled trial. Does the 
Epi-No(®) birth trainer prevent vaginal birth-related pelvic floor trauma? A multicentre 
prospective randomised controlled trial. 2016; 123(6): p. 995-1003. 
51. Lien KS, Mooney B, DeLancey J.O.L, Ashton-Miller, J.A. Levator ani muscle stretch 
induced by simulated vaginal birth. Obstet Gynecol. 2004 January; 103(1): p. 31-40. 
52. Shek KL, Dietz HP.. The effect of childbirth on hiatal dimensions.. Obstet Gynecol. 2009; 
113: p. 1272-1278. 
53. Van Delft K, Thakar R, Shobeiri SA, Sultan AH. Ultrasound Obstet Gynecol 2014; 43: 210–
217. Levator hematoma at the attachment zone as an early marker for levator ani 
muscle avulsion. Ultrasound Obstet Gynecol. 2014; 43: p. 210-217. 
54. Blasi I, Fuchs I, D'Amico R, Vinci V, La Sala GB, Mazza V, Henrich W. Intrapartum 
translabial three-dimensional ultrasound visualization of levator trauma. Ultrasound 
Obstet Gynecol. 2011 Jan; 37(1): p. 88-92. 
55. Lanzarone V, Dietz HP.. Three-dimensional ultrasound imaging of the levator hiatus in 
late pregnancy and associations with delivery outcomes.. Aust N Z J Obstet Gynaecol. 
2007; 47: p. 176-180. 
56. Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap LC III, Wenstrom KD (eds). 
Normal labor and delivery. 22nd ed.: McGraw-Hill; 2005. 
57. Torkildsen, KA; Salvesen; EggebØ TM. Agreement between two- and three-dimensional 
transperineal ultrasound methods in assessing fetal head descent in the first stage of 
labor. Ultrasound Obstet Gynecol. 2012; 39: p. 310-315. 
58. Youssef A, Maroni E, Ragusa A, De Musso F, Salsi G, Iammarino MT, Paccapelo A, Rizzo 
N, Pilu G, Ghi T. Fetal head – symphysis distance: a simple and reliable ultrasound index 
of fetal head station in labor. Ultrasound Obstet Gynecol 2013; Youssef A, Maron. Fetal 
head – symphysis distance: a simple and reliable ultrasound index of fetal head station 
in labor. Ultrasound Obstet Gynecol. 2013; 41: p. 419-424. 
59. EGGEBØ, C. HEIEN, I. ØKLAND, L. K. GJESSING, P. ROMUNDSTAD and K. A. SALVESEN. 
Ultrasound assessment of fetal head–perineum distance before induction of labor. 
Ultrasound Obstet Gynecol. 2008; 32: p. 199-204. 
60. Barbera A.F. The Angle of Progression: An Objective Assessment of Fetal Head Descent 
in the Birth Canal. In A M, editor. Intrapartum Ultrasonography for Labor Management.: 
Springer. 
61. Memon HU, Blomquist JL, Dietz HP, Pierce CB, Weinstein MM, Handa VL. Comparison of 
levator ani muscle avulsion injury after forceps-assisted and vacuum-assisted vaginal 
childbirth. Obstet Gynecol. 2015 May; 125(5): p. 1080-7. 
62. Shek K, Dietz HP. Intrapartum risk factors for levator taruma. BJOG. 2010; 117: p. 1485-

 
23
1492. 
63. Kearney R, Miller JM, Ashton-Miller JA, DeLancey JO. Obstetric factors associated with 
levator ani muscle injury after vaginal birth. Obstet Gynecol. 2006; 107: p. 144-149. 
64. Dietz HP, Simpson JM. Does delayed child-bearing increase the risk of levator injury in 
labour? Aust N Z J Obstet Gynaecol. 2007; 47: p. 491-495. 
65. Krofta L, Oteenasek M, Kasikova E, Feyereisl J. Pubococcygeus-puborectalis trauma after 
forceps delivery: evaluation of the levator ani muscle with 3D/4D ultrasound. Int 
Urogynecol J Pelvic Floor Dysfunct. 2009; 20: p. 1175-1181. 
66. Valsky DV, Lipschuetz M, Bord A, Eldar I, Messing B, Hochner-Celnikier D, Lavy Y, Hohen 
SM, Yagel S. Fetal head circumference and length of second stage of labour are risk 
factors for levator ani muscle injury, diagnosed by 3-dimensional transperineal 
ultrasound in primiparous women. Am J Obstet Gynecol. 2009; 201: p. 91.e1-7. 
67. Dietz, HP. Levator function before and after childbirth. Aust N Z J Obstet Gynaecol. 2004; 
44: p. 19-23. 
68. Buckmann E.J., Libhaber E. Accuracy of cervical assessment in the active phase of labour. 
BJOG. 2007; 114: p. 833-37. 
69. Ramphul M, Ooi PV, Burke G, Kennelly MM, Said SAT, Montgomery AA, Murphy DJ. 
Instrumental delivery and ultrasound : a multicentre randomised controlled trial of 
ultrasound assessment of the fetal head position versus standard care as an approach to 
prevent morbidity at instrumental delivery. BJOG. 2014 July; 121(8): p. 1029-38. 
70. Chou M, Kreiser D, Taslimi M, Maurice L, Druzin, Yasser T. El - Sayed. Vaginal versus 
ultrasound examination of fetal occiput position during the second stage of labor. 
American Journal of Obstetrics and Gynecology. 2004; 191: p. 521-4. 
71. Yuce T, Kalafat E, Koc A. Transperineal ultrasonography for labor management: accuracy 
and reliability. Acta Obstet Gynecol Scand. 2015 March; 94: p. 760-765.