Chorioamnionitis after premature rupture of membranes in nulliparas undergoing labor induction: prostaglandin E2 vs. oxytocin

Objectives: To assess the risk of chorioamnionitis in nulliparous, term, singleton, vertex (NTSV) pregnancies with premature rupture of membranes (PROM) and an unfavorable cervix undergoing labor induction with either prostaglandin E2 (PGE2) or oxytocin only. Methods: Retrospective cohort of NTSV pregnancies presenting with PROM who underwent labor induction with either PGE2 (n=94) or oxytocin (n=181) between October 2015 and March 2019. The primary outcome of chorioamnionitis was compared between the two groups. Statistical analysis included Chi-squared and Wilcoxon rank-sum tests, as well as logistic regression. For time to delivery, a Cox proportional hazard regression was used to determine the hazard ratio (HR) and adjusted HR (aHR). Results: Baseline characteristics were similar between the two groups. Cervical ripening with PGE2 was associated with an increased rate of chorioamnionitis (18.1 vs. 6.1%; aOR 4.14, p=0.001), increased neonatal intensive care unit admissions (20.2 vs. 9.9%; aOR 2.4, p=0.02), longer time interval from PROM to delivery (24.4 vs. 17.9 h; aHR 0.56, p=<0.0001), and lower incidence of meconium (7.4 vs. 14.4%; aOR 0.26, p=0.01), compared to the oxytocin group. Conclusions: Based on our data, the use of oxytocin appears both superior and safer compared to PGE2 in NTSV pregnancies with PROM undergoing labor induction.