Clinical trial NCT03060473
Conditions: Preterm Premature Rupture of Membranes (PPROM)
Keywords: PPROM Azithromycin Erythromycin
Sponsor: The University of Texas Medical Branch, Galveston
Start date: 2017-02-23; Completion date: 2023-12-08
Enrollment: 21 participants; Allocation: RANDOMIZED; Intervention model: PARALLEL

Brief summary:
Preterm premature rupture of membranes (PPROM) complicates 4% of pregnancies annually. This pregnancy complication is a major contributor to preterm births and results in neonatal morbidity and mortality. The current standard of care for PPROM subjects between the gestational age of 24 weeks and 0 days and 33 weeks and 6 days, is to administer ampicillin and erythromycin for a total of 7 days. Erythromycin can cause GI upset and some subjects do not tolerate this regimen over the course of 7 days. In addition, there is a national shortage of erythromycin, and published expert opinion proposed to use a second-generation macrolide (azithromycin) instead of erythromycin. Azithromycin can be taken once daily, is cheaper than erythromycin and has less GI upset adverse effects. The investigators' objective is to compare the effectiveness of the 2 regimens in prolonging pregnancy after PPROM. The investigators' working hypothesis is that there is no measurable difference in the primary outcome between the group randomized to the azithromycin regimen versus the group randomized to the erythromycin regimen.

Detailed description:
In the United States, preterm premature rupture of membranes (PPROM) complicates 4% of pregnancies annually. This pregnancy complication is a major contributor to preterm births and results in neonatal morbidity and mortality. Without treatment, 70-80% of women deliver within the 1st week following membrane rupture. Multiple trials have proven that antibiotics given to this population prolong the latency from time of PPROM to delivery, hence reducing maternal and neonatal morbidities.

According to the American College of Obstetrics and Gynecology, the current standard of care for PPROM subjects between the gestational age of 24 weeks and 0 days and 33 weeks and 6 days, is to administer ampicillin 2 gm IV every 6 hours for 48 hours followed by amoxicillin 250 mg orally every 8 hours for 5 days, with erythromycin 250 mg IV every 6 hours for 48 hours followed by 500 mg orally every 8 hours for 5 days. In this regimen, multiple doses of intravenous (IV) and oral (PO) doses of erythromycin are needed to achieve the desired outcome. Erythromycin can cause GI upset and some subjects do not tolerate this regimen over the course of 7 days. In addition, there is a national shortage of erythromycin, and published expert opinion proposed to use a second-generation macrolide (azithromycin) instead of erythromycin. This strategy was adopted nationwide including the maternal center at UTMB since 2014. Compared to erythromycin, advantages of azithromycin include:

* It is taken once orally (due to its long intracellular half-life).
* The entire regimen is much cheaper than the multiple does of erythromycin (23 doses).
* It has less gastrointestinal adverse effects.

As a result, azithromycin is now commonly being used as a substitute for erythromycin on many labor and delivery units around the country.

Despite its common use, there exists no level 1 evidence that azithromycin is equivalent to erythromycin. Haas and colleagues published a retrospective comparison of the two regimens in 2014 and concluded that the substitution of azithromycin for erythromycin in the recommended antibiotic regimen did not impact latency or any other measured maternal or fetal outcomes. This study, however, was limited by its non-randomized retrospective nature.

The investigators' objective is to compare the effectiveness of the 2 regimens in prolonging pregnancy after PPROM.

This trial will be a comparative effectiveness pragmatic randomized trial performed in singleton pregnancies with the diagnosis of PPROM between 24 weeks and 0 days - 32 weeks and 6 days. It will be comparing two well-accepted standardized treatments of care in this subject population: Erythromycin (FDA Category B) versus Azithromycin (FDA Category B). The investigators' primary outcome will be the proportion of women still pregnant by day 7 after the diagnosis of PPROM is made. The investigators' working hypothesis is that there is no measurable difference in the primary outcome between the group randomized to the azithromycin regimen versus the group randomized to the erythromycin regimen. The investigators' secondary outcome will be latency defined as interval from PPROM to delivery.

Data to be collected will consist of demographics, obstetrical history, relevant vital signs and laboratories. Examples of data to be collected but not limited to include: age, ethnicity/race, gravida, para, received tocolytics, received antenatal steroids, gestational age at rupture of membranes, reason for delivery, mode of delivery, gestational age at delivery, chorioamnionitis, date \& time of initiation of antibiotics, date \& time of delivery, placental abruption, hospital length of stay, number of women undelivered at day 7 of admission, NICU admission, infant intubation days, neonatal NEC and neonatal sepsis.

In addition, drug adverse effects profiles between the two will be assessed in a post treatment patient survey. The latter will be assessing the severity and incidence of diarrhea and other symptoms such as nausea and vomiting and their severity.

The investigators propose a total of 324 subjects will be needed to complete the study.

Arms: arm 1: Ampicillin 2 gm IV every 6 hours followed by amoxicillin 500 mg PO every 8 hours with Azithromycin 1 gm PO once at randomization. arm 2: Ampicillin 2 gm IV every 6 hours followed by amoxicillin 250 mg PO every 8 hours for 5 days with erythromycin 250 mg IV every 6 hours for 48 hours followed by 500 mg PO every 8 hours for 5 days.
Interventions: intervention 1: Azithromycin intervention 2: Erythromycin intervention 3: Ampicillin intervention 4: Amoxicillin
Intervention descriptions: intervention 1: Azithromycin 1 gm PO once intervention 2: Erythromycin 250 mg IV every 6 hours for 48 hours followed by 500 mg PO every 8 hours for 5 days. intervention 3: Ampicillin 2 gm IV every 6 hours for 2 days intervention 4: Amoxicillin 500 mg PO every 8 hours for 5 days (Azithromycin ARM) Amoxicillin 250 mg PO every 8 hours for 5 days (Erythromycin ARM)

Protocol documents:
Prot_SAP_000.pdf: 
Version 3.5 
January 23, 2023 
1 
The University of Texas Medical Branch Galveston 
Research protocol 
 
TREAT: Treatment of ppROM with Erythromycin vs. Azithromycin Trial 
 
Principal Investigator: Nkechinyere Emezienna, MD 
Funding: Departmental. 
 
1- Introduction/Background/Purpose:  
In the United States, preterm premature rupture of membranes (PPROM) 
complicates 4% of pregnancies annually. This pregnancy complication is a major 
contributor to preterm births and results in neonatal morbidity and mortality. 
Without treatment, 70-80% of women deliver within the 1st week following 
membrane rupture. Multiple trials have proven that antibiotics given to this 
population prolong the latency from time of PPROM to delivery, hence reducing 
maternal and neonatal morbidities.  
 
According to the American College of Obstetrics and Gynecology, the current 
standard of care for PPROM subjects between the gestational age of 24 weeks and 0 
days and 33 weeks and 6 days, is to administer ampicillin 2 gm IV every 6 hours for 48 
hours followed by amoxicillin 250 mg orally every 8 hours for 5 days, with 
erythromycin 250 mg IV every 6 hours for 48 hours followed by 500 mg orally every 8 
hours for 5 days. In this regimen, multiple doses of intravenous (IV) and oral (PO) 
doses of erythromycin are needed to achieve the desired outcome. Erythromycin can 
cause GI upset and some subjects do not tolerate this regimen over the course of 7 
days. In addition, there is a national shortage of erythromycin, and published expert 
opinion proposed to use a second-generation macrolide (azithromycin) instead of 
erythromycin.  This strategy was adopted nationwide including our maternal center 
at UTMB since 2014. Compared to erythromycin, advantages of azithromycin include: 
 It is taken once orally (due to its long intracellular half-life). 
 The entire regimen is much cheaper than the multiple does of erythromycin (23 
doses). 
 It has less gastrointestinal adverse effects.  
 
As a result, azithromycin is now commonly being used as a substitute for 
erythromycin on many labor and delivery units around the country. 
 
Despite its common use, there exists no level 1 evidence that azithromycin is 
equivalent to erythromycin. Haas and colleagues published a retrospective 
comparison of the two regimens in 2014 and concluded that the substitution of 
azithromycin for erythromycin in the recommended antibiotic regimen did not 
impact latency or any other measured maternal or fetal outcomes. This study, 
however, was limited by its non-randomized retrospective nature. 
 


Version 3.5 
January 23, 2023 
2 
Our objective is to compare the effectiveness of the 2 regimens in prolonging 
pregnancy after PPROM.  
 
 
2- Concise summary of project:  
This trial will be a comparative effectiveness pragmatic multi-site randomized trial 
performed in singleton pregnancies with the diagnosis of PPROM between 24 weeks 
and 0 days - 32 weeks and 6 days. It will be comparing two well-accepted 
standardized treatments of care in this subject population: Erythromycin (FDA 
Category B) versus Azithromycin (FDA Category B).  Our primary outcome will be the 
proportion of women still pregnant by day 7 after the diagnosis of PPROM is made. 
Our working hypothesis is that there is no measurable difference in the primary 
outcome between the group randomized to the azithromycin regimen versus the 
group randomized to the erythromycin regimen. Our secondary outcome will be 
latency defined as interval from PPROM to delivery.  We propose a total of 324 
subjects will be needed to complete the study. 
 
3- Participating sites: 
The following sites are participating in this trial:  
United States, UTAH 
Obstectrics & Gynecology Research Network 
Recruiting 
30 North 1900 East Suit 2B119  
Contact: Dr. Torri Metz (PI)801-587-3069  Torri.metz@hsc.utah.edu 
United States, Texas 
St. David's North Austin Medical Center 
Recruiting 
Austin, Texas, United States, 78758  
Contact: Richard T Hale, PhD    512-821-2540    Richard.Hale@stdavids.com
 
         PI : Sina Haeri     Sina.Haeri@hcahealthcare.com 
Each center had the protocol reviewed and approved independently by their local IRB 
before participating in this trial or recruiting. 
UTMB is the leading site for this trial. There is no specific accrual number per site. 
Across multi-sites, randomization is centralized. UTMB perinatal research division 
coordinates randomization assignment schedule by increments of blocks of 10 as 
enrollment is ongoing. Each block has 10 subjects randomized to either intervention 
A or B which is independent and does not affect the remaining sequence. For 
example, Block #1 has the first 10 subjects, within the block we will have 5 in 
intervention A and 5 in intervention B randomization independent of the remaining 
sequence or Block. Each site will be given 1-3 blocks of 10 increments for 
randomization. . This approach is independent of the remaining sequence or blocks, 
thus not affecting the remaining randomization sequence. 
 
4- Study procedures: 


Version 3.5 
January 23, 2023 
3 
Eligible subjects will be approached, and those who consent will be randomized to 
one of the two groups below in a 1-to-1 allocation. 
 Erythromycin group: Ampicillin 2 gm IV every 6 hours first 2 days followed by 
amoxicillin 250 mg PO every 8 hours for next 5 days with erythromycin 250 mg IV 
every 6 hours for first 2 days followed by 500 mg PO every 8 hours for next 5 days 
(standard of care at UTMB). 
 Azithromycin group: Ampicillin 2 gm IV every 6 hours first 2 days followed by 
amoxicillin 500 mg PO every 8 hours for next 5 days with azithromycin 1 gm PO 
once at randomization (Standard of care at UTMB). 
Both groups receive a total of 7 days of antibiotics as per standard of care at 
UTMB. 
The remaining standard of care will be the same for both groups concerning the 
management of PPROM according to NICHD/ACOG guidelines including GBS 
prophylaxis. 
GBS chemoprophylaxis is beyond the scope of this trial, since we are randomizing the 
portion of macrolides only and not the Ampicillin portion that actually covers GBS. As 
noted, this regimen of intravenous ampicillin/ amoxicillin, is standard on both 
interventions and covers GBS. GBS cultures and GBS treatment is left per providers’ 
discretion beyond our intervention period (7 days of latency antibiotics). 
In addition, drug adverse effects profiles between the two will be assessed in a post 
treatment subject survey. Subjects will complete a survey before being discharged 
from the hospital after receiving the assigned antibiotic regimen. Any questions will 
be answered and sufficient time will be given for the subject to fill the survey. 
Data will be collected retrospectively from EPIC EMR: 
 Time of initiation of antibiotics to delivery. 
 Maternal outcomes: chorioamnionitis, postpartum infectious morbidity, placental 
abruption 
 Route of delivery 
 Gestational age at delivery 
 Adverse events: Allergic reactions (anaphylaxis, angioedema, skin rashes including 
Stevens Johnson and Toxic Epidermal necrolysis), GI symptoms (vomiting, 
diarrhea, constipation, ileus) 
 Neonatal outcomes: perinatal death, need for oxygen supplementation (not 
intubated), ventilation support (intubated), necrotizing enterocolitis (NEC) stage 2 
or 3, duration of ventilator support (intubated), NICU days and neonatal 
infection/sepsis, individually and as a composite. 
 
 
Both survey forms and data forms are attached with protocol application. 
 
 
 
3.1 Screening, Recruitment and Consenting: 


Version 3.5 
January 23, 2023 
4 
Under the direction of the PI, trained research staff will be available 24/7 to screen 
and consent subjects according to study protocol. Medical records of all potential 
subjects with a diagnosis of PPROM will be reviewed and those who satisfy inclusion 
and exclusion criteria will be approached and a written informed consent will be 
obtained. A screening log will be used to track all subjects approached for the study. 
Potential subjects may be patients of the investigators. 
Subjects will be enrolled at the time of admission to labor and delivery (L&D) or 
thereafter. Subjects will be recruited, enrolled and consented in a private room in 
labor and delivery or antepartum units in order to respect the privacy of potential 
subjects. Subjects will be given all the time needed in order to fully understand and 
read the consent forms. All questions will be fully answered. If needed, a certified 
language interpreter will be available and Spanish consents will be used as 
appropriate. Women will only be randomized on our labor and delivery or 
antepartum units when the decision to initiate antibiotics is made, AND they 
continue to be eligible (using a randomization screen).  
 
3.2 Randomization 
A confidential computer-generated simple randomization scheme (using STATA 14, 
Dallas, Tx) will be prepared and provided on an ongoing basis to our study 
coordinator. A randomization log with group assignment, subject name and medical 
record number will be used to track the randomization process.  
Across multi-sites, randomization is centralized. UTMB perinatal research division 
synchronizes randomization assignment schedule by increments of blocks of 10 as 
enrollment is ongoing. 
 
3.3. Antibiotics Disposal and Administration 
Once a subject is consented and randomized, the appropriate antibiotics according to 
group assignment will be dispensed by the regular hospital pharmacists after order is 
placed in EPIC (as part of standard procedure at UTMB). Both drugs are standard of 
care at UTMB. This is a pragmatic/comparative effectiveness of two standard of care 
therapies. Regular hospital pharmacy currently stores and disposes the drugs and 
subject’s insurance will be responsible for paying for either antibiotic, as any other 
subject not in the study. Floor nurses will be administering antibiotics. Research staff 
will be checking medication administration record (MAR) in EPiC for compliance to 
the research protocol; if an antibiotic is withheld for any reason the staff will inform 
the PI and report it as a protocol deviation which may potentially affect the integrity 
of the data for that subject. 
 
The subject will be included in the analysis by intent-to-treat once the assigned 
antibiotics are dispensed from inpatient pharmacy and sequential number posted on 
the subject specific randomization form.  
 
3.4. Baseline Procedures  
Routine PPROM care will be provided by the subjects’ clinical providers. 


Version 3.5 
January 23, 2023 
5 
Trained and experienced research staff will be responsible for all research data 
abstraction.  
The PI will review and validate the diagnosis for all subjects identified to have the 
primary outcomes. These reviews will be conducted masked to treatment group. If 
there is uncertainty, a will review the chart, discuss with the co-investigators as 
needed and make a final determination regarding the outcome.  
Maternal and neonatal outcomes will be assessed in the hospital following the 
delivery (on an ongoing basis until discharge). 
Several data collection forms will be used during these processes. Data on these 
forms, devoid of personal identifiers, will be securely stored at our perinatal research 
division. 
  
3.5. Study visits/Follow-up  
No study visits or follow up will be needed for this study. The subject participation 
will be considered complete when the subject and her child are discharged from the 
hospital. 
 
3.6. Withdrawals 
Subjects who withdraw from the study after randomization will be excluded from 
further follow-up. Outcomes ascertained up until the time of withdrawal will be 
reported in an intent to treat fashion. Those who withdraw prior to determining the 
primary outcome will be accounted for by randomizing an equal number of additional 
subjects.  
 
3.7 Outcomes 
 
Primary outcome: 
 Proportion of undelivered subjects at day 7 from the diagnosis of PPROM 
 
Secondary outcomes: 
 Latency defined as time interval from PPROM to delivery 
 
 
Data to be collected will consist of demographics, obstetrical history, relevant vital 
signs and laboratories. Examples of data to be collected but not limited to include: 
age, ethnicity/race, gravida, para, received tocolytics, received antenatal steroids, 
gestational age at rupture of membranes, reason for delivery, mode of delivery, 
gestational age at delivery, chorioamniotis, date & time of initiation of antibiotics, 
date & time of delivery, placental abruption, hospital length of stay, number of 
women undelivered at day 7 of admission, NICU admission, infant intubation days, 
neonatal NEC and neonatal sepsis. 
In addition, drug adverse effects profiles between the two will be assessed in a post 
treatment patient survey. The latter will be assessing the severity and incidence of 
diarrhea and other symptoms such as nausea and vomiting and their severity. 


Version 3.5 
January 23, 2023 
6 
 
 
 


Version 3.5 
January 23, 2023 
7 
 
Study Summary Flow Diagram 
 
 
Assessed for eligibility  
Excluded 
   Not meeting inclusion criteria 
   Declined to participate  
   Other reasons  
After reaching our recruitment goal we will be 
analysing our data as described under section 
13 of our protocol. 
Subject participation will be ended at discharge 
of infant and mother 
Data will be collected from EMR 
Survey for side effects of intervention will be 
given to subject before discharge 
Allocated to Erythromycin Arm 
 Ampicillin 2gm IV every 6 hours followed by 
amoxicillin 250mg orally every 8 hours for 
5 days with erythromycin 250mg IV every 
6hours for 48hours followed by 500mg 
orally every 8hours for 5 days. 
Subject participation will be ended at discharge 
of infant and mother 
Data will be collected from EMR 
Survey for side effects of intervention will be 
given to subject before discharge 
Allocated to Azithromycin Arm 
 Azithromycin group: Ampicillin 2gm IV every 
6 hours followed by 500mg orally every 
8hours with azithromycin 1gram orally 
once at randomization 
After reaching our recruitment goal we will be 
analysing our data as described under section 
13 of our protocol. 
Allocation 
Analysis 
Follow-Up 
Randomized 
Enrollment on 
admission date 


Version 3.5 
January 23, 2023 
8 
 
 
 
5- Criteria for inclusion of subjects:  
 Maternal age ≥ 18 years and <50 years 
 Pregnant women between the gestational age 23 6/7 and 32 6/7 
weeks 
 Singleton pregnancy 
 Preterm premature rupture of membranes, determined clinically 
 Cervical dilation visually ≤ 5cm on sterile speculum exam. 
 
 
6- Criteria for exclusion of subjects: 
 Intrauterine fetal demise (no fetal heart beat identified and 
documented by two physicians) 
 Any contraindication to expectant management (e.g. fetal 
compromise, chorioamnionitis, placental abruption) 
 Cervical cerclage in place 
 Placenta previa or other known placental anomalies 
 Contraindication to any of the antibiotics used (allergy to macrolides). 
 Enrolled in another trial that may affect outcome. 
 Clinical chorioamnionitis or any other active bacterial infection (e.g. 
pyelonephritis, pneumonia, abscess) at time of randomization: 
because standard antibiotic therapy for these conditions may 
confound trial intervention.  
 No prenatal care (less than 2 prenatal visits) 
 Non-resident subject who is unlikely to be followed-up after delivery 
 Any fetal congenital anomaly. 
 Significant liver disease defined as known cirrhosis or elevated 
transaminases of at least 3-fold upper limit of normal 
 Significant renal disease defined as serum creatinine known to be >2.0 
mg/dl or on dialysis. 
 Active congestive heart failure (EF<45%) or pulmonary edema. 
 Immunosuppressed subjects: i.e., taking systemic immunosupressants 
or steroids (e.g. transplant subjects; not including steroids for lung 
maturity), HIV with CD4<200, or other. 
 
 
7- Sources of research material: Electronic medical records and subject 
survey. 
8- Recruitment Methods and Consenting Process: 


Version 3.5 
January 23, 2023 
9 
Please refer to section 3.1 above. 
 
9- Potential risks: 
 
7.1. Randomization Risk 
Since the antibiotic regimen type will be randomized, it is possible that one 
or more of the other treatment groups will have more benefit or lower side 
effects than the group to which subject is assigned.   
 
7.2. Loss of Confidentiality 
Any time information is collected, there is a potential risk for loss of 
confidentiality. Every effort will be made to keep the subject’s information 
confidential; however, this cannot be guaranteed.  
 
7.3 Drug Adverse Affects 
According to the FDA, Azithromycin is a macrolide and a derivative of 
erythromycin. Its mechanism of action is mediated by binding to the 50S 
ribosomal subunit of susceptible bacteria, and inhibiting protein synthesis. 
Azithromycin targets ureaplasma, aerobic and facultative gram-negative and 
gram-positive organisms, and some anaerobes. Azithromycin is classified as a 
pregnancy category B drug – animal studies using maternally toxic doses 
showed no fetal harm. However, there are no adequate well-controlled 
studies in pregnant women. It is not known whether azithromycin is 
excreted in human milk. The only absolute contraindication to its use is a 
known hypersensitivity reaction to azithromycin, erythromycin or other 
macrolide antibiotic (quite rare). There are no specific drug-drug 
interactions warranting dose adjustments when given with other 
medications. Elimination is by both renal and hepatic route, and no specific 
adjustments are mandated for subjects with renal or hepatic insufficiency. 
The long elimination 1/2-life of 68 hours is due to extensive uptake and 
subsequent release of drugs from tissues. 
The FDA does not raise any suspicion that prenatal exposure to azithromycin 
is associated with long-term adverse outcomes. Animal studies showed that 
azithromycin did not have mutagenic potential.  
Subjects receiving azithromycin may have the following adverse effects: 
 
a. Rash, increase liver enzymes, kidney dysfunction, neutropenia and 
thrombocytopenia (rare) 
b. Nausea and vomiting (3%) 
c. Diarrhea (5%) 
 
Subjects receiving erythromycin may have the following adverse effects: 
 
a. C difficile colitis, increase liver enzymes, confusion, headache (rare) 
b. Nausea and vomiting (25%) 


Version 3.5 
January 23, 2023 
10
c. Diarrhea (8%) 
 
If any of these risks occur, subjects will be managed according to standard of 
care based on the symptoms and signs/complaints. 
 
10- Subject Safety and Data Monitoring:  
The collaborators and research coordinator will be responsible for 
monitoring the safety of this study. The report will include participant 
demographics, expected versus actual recruitment rates, summary of any 
quality assurance or regulatory issues, summary of adverse events (AEs) or 
serious adverse events (SAEs) which may have occurred, and any changes in 
the protocol as a result of these issues.  This report will be prepared yearly 
and be sent to the PI’s. The collaborators and research coordinator will 
monitor for adherence to consent procedures, inclusion and exclusion 
criteria, valid abstraction, correct entry, timeliness and responsiveness to 
data queries.  Data collection will be identified with a participant ID number. 
Data will be collected and stored with the participant ID code only. The 
master enrollment log linking subject identifiers with study ID numbers will 
be kept in a password-protected database. Several data collection forms will 
be used. Data on these forms devoid of personal identifiers will be securely 
stored at our perinatal research division. The research coordinator and PIs 
will be available to monitor the data and correct any discrepancies based on 
source documents if needed. 
 
11- Procedures to Maintain Confidentiality:  
Each subject will be assigned a study number with personally identifiable 
information deleted or removed. If needed, charts will be reviewed in the 
medical records area. Subjects' information will be de-identified and tagged 
with a number. Data will be collected and stored on a UTMB password-
protected computer in a locked room. 
 
12- Potential benefits: 
In the background of erythromycin nationwide shortage, this will be the first 
level 1 trial to show that azithromycin may be equivalent to erythromycin in 
delaying delivery in patients with PPROM. This study may show for the first 
time that current alternative practice with azithromycin is as effective as 
erythromycin but with less adverse effects, less costly and easy 
administration. 
 
13- Statistical approach: Analysis will be performed by intent to treat. 
Univariable analysis (such as t-test, Mann-Whitney or Chi-square) will be 
used for descriptive statistics such as patient demographics   and assessment 
of primary outcome. Multivariable logistic analysis will be used to account 
for potential confounding variables. Sample size was calculated using a non-
inferiority trial design. Azithromycin will be tested against erythromycin for 
PPROM. The primary outcome will be the proportion of subjects undelivered 


Version 3.5 
January 23, 2023 
11
 
 
by day 7. For the sample size calculation, it is assumed the proportion 
undelivered in the erythromycin group would be 70% (pi = 0.7) based on 
Haas et al study. We considered that a difference in undelivered rate as large 
as 15% in favor of erythromycin would allow azithromycin to be non-inferior 
(delta = 0.15). This study will use 80% power to confirm non-inferiority and 
a one-sided confidence level of 97.5%. 
 
Estimated sample size for two-sample comparison of proportions (non-
inferiority) 
 
Null hypothesis: p2 - p1 呸 delta (inferior), where: 
                               pi (entered in command) is the overall proportion of participants 
                               expected to experience the outcome if the treatments 
                               are non-inferior, and delta is the smallest change in 
                               proportions between groups (p2 - p1) which would still 
                               be clinically important. 
Alternative hypothesis: p2 - p1 < delta (non-inferior) 
 
Note: a non-inferiority analysis is one-sided. 
 
Assumptions: 
         power = 0.8000 
         alpha = 0.0250 (one-sided) 
            pi = 0.7000 
         delta = 0.1500 
  estimated required sample size (per group) = 147 
 
The total estimated sample size is 294. Assuming 10% loss to follow, this study 
proposes a total of 324 subjects will be needed to complete the study. The STAT 14 
(Dallas, Tx) will be used for statistical computations. This trial will be registered 
with Clinical Trials Register (Clinicaltrials.gov), before recruitment is initiated and 
after IRB approval.” 
 
 
 
 
 


Version 3.5 
January 23, 2023 
12
References 
1. Duff, P Is azithromycin a good alternative to erythromycin for PPROM 
prophylaxis? OBG Manag. 2015 May;27(5). 
2. AU Pierson RC, Gordon SS, Haas DM SO A retrospective comparison of 
antibiotic regimens for preterm premature rupture of membranes. Obstet 
Gynecol. 2014;124(3):515.  
3. Mercer BM, Rabello YA, Thurnau GR, et al. The NICHD-MFMU antibiotic 
treatment of preterm PROM study: impact of initial amniotic fluid volume 
on pregnancy outcome. Am J Obstet Gynecol 2006; 194:438. 
4. Mercer BM, Miodovnik M, Thurnau GR, et al. Antibiotic therapy for 
reduction of infant morbidity after preterm premature rupture of the 
membranes. A randomized controlled trial. National Institute of Child 
Health and Human Development Maternal-Fetal Medicine Units Network. 
JAMA 1997; 278:989. 
5. Kenyon S, Pike K, Jones DR, et al. Childhood outcomes after prescription 
of antibiotics to pregnant women with preterm rupture of the 
membranes: 7-year follow-up of the ORACLE I trial. Lancet. 
2008;372:1310–1318.