Comparative study of second-line labor induction methods in patients with unfavorable cervix after first-line low-dose oral misoprostol.

Objective: The present study aimed to evaluate low-dose oral misoprostol induction, and compare different methods used in second-line induction in patients with a Bishop score less than 6.

Methods: This retrospective study analyzed the medical history and courses of pregnancy of all patients induced with first-line of low-dose oral misoprostol (50 μg every 4 h with a total of 200 μg/24 h) from April 2021 to June 2022 in a university hospital center, and reported outcomes according to the second-line method of induction.

Results: Among 437 labor inductions with low-dose oral misoprostol, 120 patients required a second-line induction. Predictive factors of first-line failure were higher body mass index (P = 0.011), absence of premature rupture of membranes (P = 0.021) and earlier term of pregnancy (P < 0.001). Regarding second methods of induction of labor, time from induction to delivery was shorter in the oxytocin group than the dinoprostone and misoprostol groups (24.0 vs. 41 and 51.0 h, respectively; P < 0.001), and was also significantly shorter in the dinoprostone than the misoprostol group (P = 0.048). Cesarean section rates did not differ between the three groups (P = 0.651). There were no clinically significant differences in adverse events between the groups.

Conclusion: Normal body mass index, previous rupture of membranes and later term of induction of labor were the three favoring success factors during first-line oral misoprostol. In cases of a Bishop score <6, oxytocin may be the best option to reduce duration to delivery, with the same maternal-fetal outcomes, including a similar rate of vaginal delivery.