Early versus late combined amniotomy and oxytocin after mechanical cervical ripening—a secondary analysis of a randomized controlled trial

Abstract

Purpose: The aim of this study was to compare the time to delivery between early (within 2 h) and late (after 2 h) amniotomy and oxytocin initiation in patients undergoing cervical ripening with a cervical ripening balloon (CRB). Methods: Secondary analysis of data collected from a previous parallel randomized controlled trial comparing CRB removal after 6 versus 12 h. For our study, the full cohort from the original trial was divided into patients who had amniotomy and oxytocin infusion within 2 h of CRB removal (study group) and patients who hadamniotomy and oxytocin more than 2 h after CRB removal (control group). Inclusion criteria were age > 18 years, ≥ 37 gestational weeks, Bishop score < 5, singleton vertex presentation, intact membranes, and no contraindication for vaginal delivery. Primary outcome for the current study was the time from CRB removal to delivery. Secondary outcomes included the rate of cesarean delivery and adverse maternal and neonatal outcomes. Results: A total of 197 patients were analyzed, 34 in the study group and 163 in the control group. The study and control groups did not differ in baseline characteristics but differences were observed in the treatment characteristics stemming from the division into the two groups for the analysis. Time from CRB removal to delivery was significantly shorter in the study group vs control (9 ± 6.7 vs.17 ± 11.9 h, p < 0.001) respectively. The rate of cesarean deliveries and other maternal and neonatal outcomes were similar in the two groups. Conclusion: Our findings suggest that early amniotomy and oxytocin infusion combination in patients undergoing labor induction with a CRB is associated with a shorter duration of labor and similar cesarean deliveries rate. Latent confounding remains possible.