Background:In China,no multicenter double-blinded prospective randomized controlled study on labor induction has been conducted till now.This study is to evaluate the efficacy and safety of intravaginal accurate 25-μg misoprostol tablets for cervical ripening and labor induction in term pregnancy in nulliparous women.Methods:This was a double-blinded,prospective randomized controlled study including nulliparous women from 6 university hospitals across China.Subjects were randomized into misoprostol or placebo group with the sample size ratio set to 7:2.Intravaginal 25-μg misoprostol or placebo was applied at an interval of 4 h (repeated up to 3 times) for labor induction.Primary outcome measures were the incidence of cumulative Bishop score increases ≥3 within 12 h or vaginal delivery within 24 h.Safety assessments included the incidences of matal morbidity and adverse fetal/neonatal outcomes.Results:A total of 173 women for misoprostol group and 49 women for placebo were analyzed.The incidence of cumulative Bishop score increases ≥3 within 12 h or vaginal delivery within 24 h was higher in the misoprostol group than in the placebo (64.2％ vs.22.5％,relative risk [RR]:2.9,95％ confidence interval [CI]:1.4-6.0).The incidence of onset of labor within 24 h was significantly higher in the misoprostol group than in the placebo group (48.0％ vs.18.4％,RR:2.6,95％ CI:1.2-5.7);and the induction-onset of labor interval was significantly shorter in the misoprostol group (P =0.0003).However,there were no significant differences in the median process time of vaginal labor (6.4 vs.6.8 h;P =0.695),incidence (39.3％ vs.49.0％,RR:0.8,95％ CI:0.4-1.5) and indications (P =0.683) of cesarean section deliveries,and frequencies of matal,fetal/neonatal adverse events between the groups.Conclusion:Intravaginal misoprostol 25 μg every 4 h is efficacious and safe in labor induction and cervical ripening.