Comparison of two management options for labor induction following unsuccessful prostaglandin E2 ripening

We sought to compare the likelihood of a vaginal delivery (VD) using oxytocin, with and without a cervical ripening balloon, in nulliparous women who did not respond to initial ripening with prostaglandin E2 (PGE2).

We a performed a retrospective cohort study of nulliparous women with a singleton pregnancy at term who underwent cervical ripening with vaginal PGE2 between October 2015 and March 2019. Patients who did not respond to PGE2 ripening (bishop score (BS) of 6 or less with cervical dilation less than 3 cm) were stratified into two groups based on management: sequential ripening with a cervical ripening balloon in addition to oxytocin versus oxytocin alone. Patients who had PGE2 for less than 6 h, a BS greater than 6 after ripening, rupture of membranes or missing data were excluded. The primary outcome was VD. Secondary outcomes included VD within 24 h of induction, time from induction to delivery, rates of chorioamnionitis and postpartum hemorrhage, presence of meconium, neonatal birthweight, NICU admission, 5 min apgar < 5, and umbilical cord pH < 7. Statistical analysis included Chi-squared, Fisher's exact and Mann-Whitney U tests, as well as logistic regression. Odds ratios (ORs) were calculated and adjusted for significant confounders using backwards-stepwise logistic regression. For time to delivery, a Cox proportional hazard regression was used to determine the hazard ratio (HR) and adjusted HR.

840 patients underwent cervical ripening with PGE2 during the study period. After the exclusion criteria were applied, 272 cases comprised the study cohort. Of those, 123 (45%) continued labor induction with a cervical ripening balloon and oxytocin and 149 (55%) continued labor induction with oxytocin alone. Baseline characteristics such as age, BMI, ethnicity, gestational age at induction and number of women undergoing elective induction were similar between both groups. There was no statistically significant difference in the likelihood of VD (oxytocin and cervical ripening balloon: 62.6% vs. oxytocin alone: 50.3%; a OR 1.61, p = .07) or rate of secondary outcomes between the two groups. Patients in the oxytocin alone group had a higher BS after PGE2 ripening, although both were very low (3 vs. 2, p < .0001).". Additionally, there were significantly more patients undergoing full PGE2 ripening for 12 h in the cervical ripening balloon and oxytocin group compared to oxytocin alone (65.9% vs. 49.7%, p = .02).

Our data did not show a difference in VD rate in nulliparous women unresponsive to PGE2 ripening who underwent continued induction with oxytocin and cervical ripening balloon compared to oxytocin alone. Larger studies investigating the utility of sequential ripening and determining the optimal induction method following unsuccessful ripening are needed.