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. Keywords : Oral misoprostol, Misoprostol solution, Low dose, Labor induction, Cervical ripenting, Vaginal delivery DOI : doi.org/10.35755/jmedassocthai.2021.04.12111 Received 14 October 2020 | Revised 11 January 2021 | Accepted 11 January 2021