Randomized trial of two doses of the prostaglandin E-1 analog misoprostol for labor induction

OBJECTIVE: Our purpose was to compare the safety and effectiveness of intravaginally administered misoprostol at doses of 25 mu g and 50 mu g for indicated labor induction in patients with an unfavorable cervix. STUDY DESIGN: Three hundred ninety-nine patients received either 25 mu g or 50 mu g of misoprostol, placed intravaginally in the posterior fornix, in this randomized double-blind trial. The dose was repeated every 3 hours until adequate labor was achieved (at least three contractions in 10 minutes). RESULTS: Among 399 patients evaluated, 192 patients were allocated to the 25 mu g group and 207 patients to the 50 mu g group. The start-to-delivery interval was shorter in the 50 mu g group (826 minutes vs 970 minutes, p = 0.02). The incidence of vaginal delivery after one dose was higher in the 50 mu g group (38.2% vs 25.0%, p = 0.007). Patients receiving 25 mu g required oxytocin augmentation more frequently than did those receiving 50 mu g (27.1% vs 16.9%, p = 0.02). No differences were noted in the cesarean or other operative delivery rates among patients in the two treatment groups. The incidence of newborns with a cord pH <7.16 was greater in the 50 mu g group (13.0% vs 6.8%, p = 0.04). Although the incidence of hyperstimulation was similar between the groups, the incidence of tachysystole was higher in the 50 mu g group (32.8% vs 15.6%, p = 0.0001). CONCLUSIONS: Although a dose of 50 mu g is associated with a shorter start-to-delivery interval and a higher incidence of vaginal delivery after one dose, 25 mu g of intravaginal misoprostol is effective and associated with a lower incidence of tachysystole and cord pH values <7.16.