Failed induction of labor in term nulliparous women with an unfavorable cervix: comparison of cervical ripening by two forms of vaginal prostaglandins (slow-release pessary and vaginal gel).

OBJECTIVE: To compare the rate of failed induction after cervical ripening by two forms of vaginal prostaglandins.

MATERIAL AND METHODS: This two-year retrospective study (January 1, 2016, through December 31, 2017) in two tertiary maternity units included nulliparous women with a singleton fetus in cephalic presentation and an unfavorable cervix requiring labor induction for prolonged pregnancy. The principal endpoint was the rate of failed induction, defined by the performance of a cesarean delivery before 6 cm of dilation. Cervical ripening was initiated by prostaglandins for 24 hours, using a slow-release pessary (unit A) or a vaginal gel (unit B). The care protocol of the two groups after the first 24 hours were similar. The women's individual characteristics were compared between the two units. The rates of failed induction were then compared between the two units, first by univariate and then by multivariable analysis adjusted for the characteristics that differed significantly between the units.

RESULTS: Among the 17,217 women delivered in the two maternity units during the study period, 178 met our inclusion criteria (125 in unit A (slow-release pessary) and 53 in unit B (vaginal gel)). The rate of failed induction was similar: 21.6% in unit A (slow-release pessary) and 17.0% in unit B (vaginal gel) (P=0.48). The multivariate analysis did not show any difference about failed induction, time from the onset of induction to delivery, and vaginal delivery rate within 24h.

CONCLUSION: The rate of failed induction of labor did not differ between slow-release pessary and vaginal gel.