Mechanical and Pharmacologic Methods of Labor Induction: A Randomized Controlled Trial

Abstract

Objective: To evaluate the effectiveness of four commonly used induction methods.

Methods: This randomized trial compared four induction methods: misoprostol alone, Foley alone, misoprostol-cervical Foley concurrently, and Foley-oxytocin concurrently. Women undergoing labor induction with full-term (37 weeks of gestation or greater), singleton, vertex-presenting gestations, with no contraindication to vaginal delivery, intact membranes, Bishop score 6 or less, and cervical dilation 2 cm or less were included. Women were enrolled only once during the study period. Our primary outcome was time to delivery. Neither patients nor health care providers were blinded to assigned treatment group because examinations are required for placement of all methods; however, research personnel were blinded during data abstraction. A sample size of 123 per group (n=492) was planned to compare the four groups pairwise (P≤.008) with a 4-hour reduction in delivery time considered clinically meaningful.

Results: From May 2013 through June 2015, 997 women were screened and 491 were randomized and analyzed. Demographic and clinical characteristics were similar among the four treatment groups. When comparing all induction method groups, combination methods achieved a faster median time to delivery than single-agent methods (misoprostol-Foley: 13.1 hours, Foley-oxytocin: 14.5 hours, misoprostol: 17.6 hours, Foley: 17.7 hours, P<.001). When censored for cesarean delivery and adjusting for parity, women who received misoprostol-Foley were almost twice as likely to deliver before women who received misoprostol alone (hazard ratio 1.92, 95% confidence interval [CI] 1.42-2.59) or Foley alone (hazard ratio 1.87, 95% CI 1.87 1.39-2.52), whereas Foley-oxytocin was not statistically different from single-agent methods.

Conclusion: After censoring for cesarean delivery and adjusting for parity, misoprostol-cervical Foley resulted in twice the chance of delivering before either single-agent method.

Clinical trial registration: ClinicalTrials.gov, https://ichgcp.net/clinical-trials-registry/NCT01916681" title="See in ClinicalTrials.gov">NCT01916681.

Figures

Figure 1

Flowchart of patients enrolled.

Figure 2

Estimated time to delivery by study group. This figure displays the Kaplan-Meier survival curves for time to delivery for the four induction method groups, P<.001.