104: Is more than one dose of misoprostol needed to expedite vaginal delivery in a patient with an unripe cervix? - a randomized controlled study

Abstract

Misoprostol is a common agent used to induce labor, yet there is no clear evidence of the optimal number of doses needed to achieve a higher rate of vaginal delivery. Our objective was to compare the rate of vaginal delivery within 24 hours between a one-dose and a multiple-dose regimen of misoprostol for induction of labor. A randomized controlled trial was conducted from March 2016 to March 2017 comparing a single dose to up to four doses of misoprostol. Randomization was stratified by parity. Women with a singleton pregnancy ≥ 37 weeks gestation with intact membranes admitted for labor induction with a Bishop score ≤ 6 were included. Our primary outcome was vaginal delivery (VD) rate within 24 hours. Secondary outcomes included time to VD and cesarean delivery (CD) rate. Student t-test, Mann-Whitney test, chi-square and Fisher's exact test were performed as appropriate with an intent-to-treat principle. Based on a power of 80% and an alpha of 0.05, a sample size of 220 patients was needed to detect a 20% increase in VD rate within 24 hours in the one-misoprostol group. 250 women were randomized. Demographics and clinical characteristics were similar between groups. In the univariate analysis, there was no difference in the VD rate within 24 hours between the one-misoprostol group and the multiple-dose group (65.5% vs. 57.9%, respectively p=NS) or time to VD (1263 min vs. 1385 min, respectively, p=NS). The one-misoprostol group had a greater CD rate (35% vs. 22.2%, p=0.035). In a multivariate analysis controlling for Bishop score prior to starting oxytocin, parity, gestational age, body mass index and birth weight, treatment group was no longer associated with CD rate. Instead, Bishop score of < 4 prior to initiation of oxytocin and nulliparity were significantly associated with higher CD rate (p<0.001, p=0.001 respectively). In this first randomized controlled trial comparing one to multiple doses of misoprostol, we found that the one-dose regimen is an acceptable alternative for induction of labor, especially for multiparous women and for patients with a Bishop score > 4 after the first dose of misoprostol.View Large Image Figure ViewerDownload Hi-res image Download (PPT)