EXPERT COMMENTARY
The concurrent use of mechanical and pharmacologic cervical ripening is an area of active interest. Combination methods typically involve placing a Foley catheter and simultaneously administering either prostaglandins or oxytocin. Despite the long-standing belief that using 2 cervical ripening agents simultaneously has no benefit compared with using only 1 cervical ripening agent, several recent large randomized trials are challenging this paradigm by suggesting that using 2 cervical ripening agents together may in fact be superior.
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Details of the study
Schoen and colleagues conducted a randomized controlled trial that included 184 nulliparous and 139 multiparous women with an unfavorable cervix undergoing induction of labor after 24 weeks of gestation. All participants had a Foley catheter placed intracervically and then were randomly assigned to receive either concurrent oxytocin infusion within 60 minutes or no oxytocin until after Foley catheter expulsion or removal. Nulliparous and multiparous women were randomly assigned separately. Women with premature rupture of membranes and with 1 prior cesarean delivery were included in the trial, but women were excluded if they were in active labor, had suspected abruption, or had a nonreassuring fetal tracing.
The study was powered to detect a 20% increase in total delivery rate within 24 hours of Foley placement, which was the primary study outcome. Secondary induction outcomes of note included time to Foley expulsion, time to second stage, delivery within 12 hours, total time to delivery, duration of oxytocin use, and mode of delivery. Several maternal and neonatal outcomes also were examined, including tachysystole, chorioamnionitis, meconium, postpartum hemorrhage, birth weight, maternal intensive care unit (ICU) admission, and neonatal ICU admission.
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Women receiving concurrent Foley and oxytocin delivered sooner. Among nulliparous women, the overall rate of delivery within 24 hours of Foley catheter placement was 64% in the Foley with concurrent oxytocin group compared with 43% in those who received a Foley catheter alone followed by oxytocin (P = .003). The overall time to delivery was 5 hours less in nulliparous women who received combination cervical ripening compared with those who had a Foley catheter alone.
Similarly, multiparous women had an overall rate of delivery within 24 hours of 87% in the concurrent Foley and oxytocin group compared with 72% in women who received Foley catheter followed by oxytocin (P = .022).
Meanwhile, there were no statistically significant differences in mode of delivery between groups for either multiparous or nulliparous patients, and there were no differences in adverse maternal or neonatal outcomes between groups.
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Study strengths and weaknesses
This well-designed, randomized control trial clearly demonstrated that the combination of Foley catheter and oxytocin for cervical ripening increases the rate of delivery within 24 hours compared with use of Foley catheter alone. This finding is consistent with those of 2 other large randomized trials in the past 2 years that similarly demonstrated reduced time to delivery when oxytocin infusion was used in combination with Foley catheter compared with Foley alone.1,2
Despite these findings, important questions remain regarding concurrent use of cervical ripening agents. The study by Schoen and colleagues does not address the other option for dual cervical ripening, namely, concurrent use of Foley catheter and misoprostol. Several large randomized trials using Foley catheter with vaginal or oral misoprostol demonstrated reduced time to delivery compared with using either method alone.1,3,4 Only 1 randomized study has compared these 2 dual cervical ripening regimens head-to-head; that study demonstrated that the misoprostol and Foley combination significantly reduced time to delivery compared with combining Foley catheter and oxytocin together.1
Additionally, it is important to note that the study by Schoen and colleagues was not large enough to adequately evaluate potential safety risks with dual combination cervical ripening. More safety data are needed before combination cervical ripening methods can be recommended universally.
Combination cervical ripening, in which both a mechanical and a pharmacologic cervical ripening agent are used simultaneously, may be employed for induction of labor in both nulliparous and multiparous women with an unfavorable cervix. However, more safety data and comparative effectiveness studies of Foley catheter with misoprostol versus Foley catheter with oxytocin are needed before 1 combination regimen can be recommended over the other.
-- Christina A. Penfield, MD, MPH, and Deborah A. Wing, MD, MBA
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