Objective: To evaluate the efficacy of intravaginal prostaglandin E1 methyl analogue misoprostol in cervical ripening in patients with unfavorable cervix (Bishop score < 4) requiring labor induction.

Method: A randomized controlled clinical trial of 62 women in the third trimester with various indications for induction of labor were randomly allocated to receive either 100 μg misoprostol inserted vaginally (32) or placebo similarly applied (30). Transvaginal sonography was performed to measure the cervical length before and 12 hrs after insertion.

Results: The mean change in cervical length and Bishop score was significantly greater in the misoprostol group (24 mm and score 8) compared with in the placebo group (2.2 mm and score 1) (p = 0.001). All but one patients receiving misoprostol went into labor while only one in the placebo group did so. The interval from insertion to vaginal delivery was significantly shorter in the misoprostol group (12.0 vs 25.5 hrs, p < 0.001). Delivery occurred within 24 hrs in 75% and 30% of patients in the misoprostol and placebo groups respectively. Uterine tachysystole occurred more frequently in the misoprostol group (38%) than in the placebo group (0%) (p < 0.001). All could be rapidly reversed by tocolytics without apparent untoward intrapartum effects. No significant differences were noted in the 2 groups in terms of perinatal outcomes and mode of delivery.

Conclusion: Intravaginal misoprostol is an effective, cheap and safe method for cervical ripening. The higher frequency of uterine tachysystole in the misoprostol group did not increase the risk of adverse intrapartum and neonatal outcomes.