PGE2 Followed by Oxytocin vs Oxytocin in Term PROM (POXY-PROM)

Comparison of the Effectiveness of Labor Induction Using Dinoprostone Followed by Oxytocin Versus Oxytocin Alone in Term Pregnancies With Premature Rupture of Membranes and an Unfavorable Cervix - A Randomized Clinical Trial

This study is being done to learn more about the best way to start labor for pregnant women whose water breaks at term before labor begins, a condition called term prelabor rupture of membranes (term PROM). When this happens and the cervix is not ready for labor, it is unclear which induction method works best and is safest for mother and baby.

The purpose of this study is to compare two common ways to induce labor in women with term PROM and an unfavorable cervix (Bishop score ≤ 6). One group will receive a vaginal dinoprostone insert (Propess) for 6 hours to soften the cervix, followed by oxytocin if labor does not start. The other group will receive immediate oxytocin through a vein.

Pregnant women aged 18 years or older with a single baby in head-down position at 37-42 weeks, whose water has broken and whose cervix is not yet favorable, may be able to join this study. All care will be provided at the National Hospital of Obstetrics and Gynecology in Hanoi, Vietnam, where both medicines are already used in routine practice.

The main outcome is how many women have a vaginal birth. The study will also look at how long it takes from induction to birth, complications for mothers and babies, and women's experiences of labor. The results may help doctors choose the safest and most effective way to induce labor for women with term PROM in the future.

Prelabor rupture of membranes at term (term PROM) occurs in approximately 8% of pregnancies and is associated with increased risks of maternal infection, neonatal morbidity, and cesarean delivery when labor does not begin promptly. International guidelines recommend active induction of labor for women with term PROM; however, the optimal induction strategy for women presenting with an unfavorable cervix (Bishop score ≤ 6) remains uncertain.

Oxytocin is widely used for induction of labor and is effective when the cervix is favorable, but its efficacy may be reduced in the presence of an unripe cervix. Prostaglandin E2 (dinoprostone) is commonly used for cervical ripening and may improve the likelihood of vaginal delivery when administered prior to oxytocin. Previous randomized trials comparing dinoprostone followed by oxytocin with oxytocin alone have suggested potential benefits, but the available evidence is limited by small sample sizes and inconsistent results. Additional high-quality randomized evidence is therefore required to guide clinical practice in this population.

This randomized controlled trial compares two induction strategies for women with term PROM and an unfavorable cervix: (1) cervical ripening using a 6-hour vaginal dinoprostone (Propess) insert followed by intravenous oxytocin if labor has not commenced, and (2) immediate induction with intravenous oxytocin alone. Both interventions are routinely used in clinical practice in Vietnam and are considered safe.

Participants are randomly assigned in a 1:1 ratio using a computer-generated randomization sequence with variable block sizes of 4 and 6, with allocation concealment ensured through centralized randomization. Randomization is performed after confirmation of eligibility and completion of the informed consent process. Participants remain in their assigned study arm throughout the trial, and no crossover between arms is permitted. All aspects of intrapartum care, including fetal heart rate monitoring, assessment of labor progress, and management of uterine tachysystole or other complications, are conducted according to standard institutional protocols.

The primary outcome of the study is vaginal delivery. Secondary outcomes are selected in accordance with the internationally developed core outcome set for trials on induction of labour and include key maternal, neonatal, and patient-reported outcomes. Maternal outcomes include mode of delivery, time from induction to delivery, need for oxytocin augmentation, uterine hyperstimulation, postpartum hemorrhage, maternal infection, admission to intensive care, hysterectomy, and maternal death. Neonatal outcomes include Apgar scores, admission to the neonatal intensive care unit, neonatal infection, hypoxic-ischemic encephalopathy or need for therapeutic hypothermia, and neonatal death. Patient-reported outcomes, including overall labor pain and maternal satisfaction with the birth process, are also assessed.

A total sample size of 450 participants has been calculated to provide adequate statistical power while accounting for potential attrition. The findings of this study are expected to clarify whether cervical ripening with dinoprostone prior to oxytocin induction improves clinically meaningful outcomes for women with term PROM and an unfavorable cervix, and may help inform future national and international guidelines on induction of labor.

Inclusion Criteria

• Maternal age ≥ 18 years

• Gestational age from 37 to 42 weeks, determined by last menstrual period or by a first- or second-trimester ultrasound

• Live singleton fetus

• Prelabor rupture of membranes (PROM) confirmed by at least one of the following:

  • Amniotic fluid visibly draining from the cervical os during sterile speculum examination
  • Pool of fluid in the posterior fornix

• Cephalic presentation

• Bishop score ≤ 6

• No spontaneous uterine contractions

• No contraindications for vaginal delivery

Exclusion Criteria:

• Active labor
• Previous uterine surgery (e.g., cesarean section)
• Chorioamnionitis or non-reassuring fetal status
• Major fetal anomalies
• Contraindications to prostaglandin or vaginal delivery
• Refusal to participate