Effectiveness of sequential low dose oral misoprostol solution for induction of labor: An experience in a Thai quaternary hospital

Background: Siriraj Hospital has seen remarkably high cesarean section rates during the last decade. A labor induction protocol has been established to reduce cesarean section rate from “failed induction”. Objective: To determine effectiveness of a sequential low dose misoprostol solution protocol for labor induction. Cervical ripening and vaginal delivery rates, pregnancy outcomes, and associated factors of successful vaginal delivery were determined. Materials and Methods: The present study was a retrospective observational study. Medical records of women with a term singleton pregnancy and with Bishop score of 6 or less who underwent labor induction were reviewed. The induction protocol started with series 1 which was 25 mL oral misoprostol solution (1 mcg/mL) every two hours for a maximum of 24 hours. If Bishop score was 6 or less by the end of series 1, then series 2 would follow, comprising 50 mL oral misoprostol solution (1 mcg/mL) every four hours for a maximum of 24 hours. Data of Bishop scores, delivery route by the end of each series, pregnancy outcomes, and possible associated factors were collected. Results: One hundred twenty-eight women were analyzed. The overall rate of cervical ripening, with a Bishop score of more than 6, was 92.2%, and at 88.3% with series 1 only. Successful vaginal delivery was achieved in 70 cases (54.7%), 53 of whom were delivered within 24 hours. Significantly associated factors with successful vaginal delivery were multiparity, and birth weight of 3,200 grams or less; adjusted OR 4.0 (95% CI 1.31 to 12.16, p=0.015) and 3.4 (95% CI 1.48 to 7.63, p=0.004), respectively. No serious adverse pregnancy outcomes were observed. Conclusion: With Siriraj induction protocol, success rates of cervical ripening and vaginal delivery were 92.2% and 54.7%, respectively, without serious adverse outcomes. Significant associated factors of successful vaginal delivery were multiparity and birth weight of 3,200 grams or less.