Oxytocin vs oral misoprostol for PROM induction in nulliparas with unfavorable cervix: a randomized trial

Induction of labor (IOL) is recommended following prelabor rupture of membranes (PROM). The optimal method for IOL and need for cervical ripening in those with PROM and an unfavorable cervical examination is unclear.

To determine if oxytocin or oral misoprostol results in a shorter time to delivery among nulliparous patients with an unfavorable cervical examination and PROM diagnosis and to evaluate patient satisfaction with both methods.

This is a randomized clinical trial conducted at an urban tertiary care center from 2019 to 2023. Subjects were nulliparas ≥36 weeks with an unfavorable starting cervical exam (≤2 cm and Bishop <8). The primary outcome was time from IOL to delivery in hours compared between oxytocin vs oral misoprostol. Secondary outcomes included suspected intraamniotic infection, cesarean delivery, composite maternal and neonatal morbidity, and patient satisfaction (assessed by Birth Satisfaction Scale-Revised). Sub-group analyses for those with BMI ≥ 30 kg/m² and cervical dilation ≥1 cm were performed. We required 148 subjects to have 80% power to detect a 2-hour difference in time to delivery. The study was stopped early by the data safety monitoring board due to feasibility concerns in recruiting desired sample size.

A total of 108 subjects were randomized: 56 oxytocin; 52 oral miso. The median gestational age at induction was 39.5 weeks; the mean starting cervical dilation was 1.1 cm. There was no statistical difference in time to delivery between groups overall: 14.9 hours oxytocin vs 18.1 hours oral misoprostol (P=.06). In sub-group analyses, there was a 5 hours shorter time to delivery with oxytocin for those with a BMI ≥ 30 kg/m² (16.6 hours oxytocin vs 21.8 hours oral misoprostol, P .04) and 4.5 hours shorter time to delivery with oxytocin for those with cervix ≥1 cm (12.9 hours oxytocin vs 17.3 hours oral misoprostol, P .04). There were no differences in intraamniotic infection, cesarean delivery, maternal or neonatal morbidity between the groups. Patient satisfaction was higher for those receiving oxytocin compared to misoprostol (29.0 vs 26.3, P=.03).

Among nulliparas with PROM and an unfavorable cervix, there was no difference in overall time to delivery between oxytocin and oral misoprostol. This result should be interpreted with caution given early study discontinuation and inadequate power. However, a shorter time to delivery with oxytocin was noted in obese patients and those with cervical dilation of at least 1 cm. Furthermore, patient satisfaction was higher in the oxytocin group, and there was no increased risk of neonatal or maternal morbidity with oxytocin.