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

Abstract

The optimal timing of amniotomy during labor induction is a topic of ongoing debate due to the potential risks associated with both amniotomy and prolonged labor. As such, individuals in the field of obstetrics and gynecology must carefully evaluate the associated benefits and drawbacks of this procedure. While amniotomy can expedite the labor process, it may also lead to complications such as umbilical cord prolapse, fetal distress, and infection. Therefore, a careful and thorough examination of the risks and benefits of amniotomy during labor induction is essential in making an informed decision regarding the optimal timing of this procedure. This study aimed to determine if an amniotomy within 2 hours after Foley balloon removal reduced the duration of active labor and time taken to achieve vaginal delivery when compared with an amniotomy ≥4 hours after balloon removal among term pregnant women who underwent labor induction. This was an open-label, randomized controlled trial that was conducted at a single academic center from October 2020 to March 2023. Term participants who were eligible for preinduction cervical ripening with a Foley balloon were randomized into 2 groups, namely the early amniotomy (rupture of membranes within 2 hours after Foley balloon removal) and delayed amniotomy (rupture of membranes performed more than 4 hours after Foley balloon removal) groups. 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 delivery rates, and maternal and neonatal complications, were analyzed using intention-to-treat and per-protocol analyses. Of the 150 participants who consented and were enrolled, 149 were included in the analysis. In the intention-to-treat population, an early amniotomy did not significantly shorten the time between Foley balloon insertion and active labor when compared with a delayed amniotomy (885 vs 975 minutes; P=.08). An 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=.02). When evaluating the secondary outcomes, an early amniotomy was associated with a significantly shorter time to active labor onset (312.5 vs 442.5 minutes; P=.02) and delivery (484 vs 587 minutes; P=.03) from Foley balloon removal with a higher rate of delivery within 36 hours (96% vs 85%; P=.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, 1.5; 95% confidence interval, 1.1-2.2; P=.02). Those with an early amniotomy also reached vaginal delivery 1.5 times faster after Foley balloon removal than those in the delayed group (hazard ratio, 1.5; 95% confidence interval, 1-2.2; P=.03). A delayed amniotomy was associated with a higher rate of postpartum hemorrhage (0% vs 9.5%; P=.01). No significant differences were observed in the cesarean delivery rates, length of hospital stay, maternal infection, or neonatal outcomes. Although an early amniotomy does not shorten the 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.