Predictors of successful labor induction with oral or vaginal misoprostol

Objective: To identify independent predictors of successful labor induction with oral or vaginal misoprostol. Methods: Women enrolled in four previous randomized trials involving oral or vaginal misoprostol for cervical ripening and labor induction were included in the present cohort study, with dosing of 25-50 μg every 4 to 6 h vaginally (n = 574) or 50 μg every 4 h orally (n = 207). Multiple logistic regression was performed to identify factors independently associated with successful labor induction - defined as vaginal delivery within 12 h, vaginal delivery within 24 h and spontaneous vaginal delivery. Predictors of Cesarean birth and the need for only one dose of misoprostol were also identified. Variables included in the models were maternal age, weight, height, parity, gravidity, membrane status, route of misoprostol, gestational age, birth weight, and Bishop score and its individual components. Results: Maternal age, height, weight, parity, birth weight, dilatation, effacement and cervical station were associated with vaginal delivery within 24 h of induction. Maternal age, height, weight, nulliparity, birth weight and route of misoprostol were associated with Cesarean birth, with oral misoprostol being associated with a lower rate of Cesarean birth. The need for only one dose of misoprostol was predicted by maternal height, weight, parity, gestational age, Bishop score and route of misoprostol. Conclusion: Characteristics of the woman (height, weight, parity), the fetus (birth weight) and some of the individual components of the Bishop score, were associated with successful labor induction, with oral misoprostol being associated with a lower rate of Cesarean birth.