Cervical change times during induction in nulliparas using vaginal or buccal misoprostol

To determine if the time to cervical change and time to active labor were different when misoprostol was administered by a vaginal or buccal route for cervical ripening in nulliparas undergoing labor induction at term.

This was a secondary analysis of nulliparous participants in the IMPROVE Study-A comparison of vaginal versus buccal misoprostol for cervical ripening for labor induction at term: a triple-masked randomized controlled trial (NCT02408315). The parent study was a non-inferiority randomized controlled trial in which patients beginning induction with a modified Bishop score ≤6 received either vaginal or buccal misoprostol and simultaneous placebo via the opposite route. The primary outcome of the parent study was time to delivery. Primary outcomes for this secondary analysis were the time to active labor (at least 6 cm dilated) and time to change in cervical dilation. Kaplan-Meier analysis was used to compare routes for time to active labor and multistate Markov modeling was used to compare sojourn times at each cervical dilation.

Of the 300 participants enrolled in the parent trial, 124 (41.3%) were nulliparous; 59 (47.6%) nulliparous participants underwent induction with vaginal misoprostol and 65 (52.4%) received buccal dosing. Nulliparas receiving vaginal dosing required fewer doses of misoprostol to reach active labor (median 2 vs 3, p = .003). However, this did not result in shorter time to active labor (median vaginal 23.1 h, 95% CI = [21.6, 27.2 h]; buccal 25.6 h [21.5, 29.3 h], p = .45) or higher rate of vaginal delivery within 24 h; (33.9% vs 35.4%, p = .86). There was also no significant difference in time to active labor after adjusting for covariates (adjusted HR for dose route (buccal vs vaginal) = 0.91 [0.61, 1.36], p = .649). Among people that delivered vaginally, the mean sojourn times, measuring cervical dilation state change, were not significantly different, with mean duration to active labor of 20.5 [17.6, 24.5] h for buccal and 21.8 [17.7, 28.2] h for vaginal dosing (p = .092). Satisfaction and preference for dosing routes were not different between groups.

Buccal and vaginal dosing of misoprostol for cervical ripening in nulliparas appear to have similar times to active labor and progression of cervical change during ripening.