Early versus delayed amniotomy following transcervical Foley balloon in the induction of labor: a randomized clinical trial.

To determine if amniotomy within two hours after Foley balloon removal compared with amniotomy four hours or later reduces the duration of active labor and time taken to achieve vaginal delivery in term pregnant women undergoing labor induction. An open-label, randomized controlled trial was conducted at a single academic center from October 2020 to March 2023. Term participants eligible for pre-induction cervical ripening with Foley balloon were randomized into two groups: early amniotomy (rupture of membranes within two hours after Foley balloon removal) and delayed amniotomy (rupture of membranes performed more than four hours after Foley balloon removal). Randomization was stratified by parity. The primary outcome was time from Foley balloon insertion to active phase of labor. Secondary outcomes, including time to delivery, cesarean section rates, and maternal and neonatal complications, were analyzed using intention-to-treat and per-protocol analyses. Of the 150 consented and enrolled participants, 149 were included in the analysis. In the intention-to-treat population, early amniotomy did not significantly shorten the time between Foley balloon insertion and active labor when compared to delayed amniotomy (885 vs. 975 minutes, P=0.08). Early amniotomy was associated with a significantly shorter time from Foley balloon placement to active labor in nulliparous individuals (1211 [584-2340) vs. 1585 (683-2760), P=0.02). When evaluating secondary outcomes, early amniotomy was associated with a significantly shorter time to active labor onset (312.5 vs. 442.5 minutes, P=0.02) and delivery (484 vs. 587 minutes, P=0.03) from Foley balloon removal, with a higher rate of delivery within 36 hours (96% vs. 85%, P=0.03). Individuals in the early amniotomy group reached active labor 1.5 times faster after Foley balloon insertion than those in the delayed group (hazard ratio (HR), 1.5; 95% confidence interval, 1.1-.2.2; P=0.02). Those with early amniotomy also reached vaginal delivery 1.5 times faster following Foley balloon removal than those in the delayed group (HR, 1.5; 95% [1-.2.2]; P=0.03). Delayed amniotomy was associated with a higher rate of postpartum hemorrhage (0% vs. 9.5%, P=0.01). No significant differences were observed in cesarean rates, length of hospital stay, maternal infection, or neonatal outcomes. While early amniotomy does not shorten time from Foley balloon insertion to active labor, it shortens time from Foley balloon removal to active labor and delivery without increasing complications. The increased postpartum hemorrhage rate in the delayed amniotomy group suggests increased risks with delayed amniotomy.

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