ObjectiveTo compare the efficacy and safety of two prostaglandin derivatives, misoprostol and dinoprostone, for ripening the cervix and inducing labor in women with an unfavorable cervix.MethodsOne hundred fifty-five women admitted for induction of labor to St. John's Mercy Medical Center, a teaching community hospital, were randomized to one of two methods: intravaginal misoprostol, 50 μg every 4 hours up to three doses (n= 76); and intracervical dinoprostone gel, 0.5 mg every 6 hours up to three doses (n= 79).ResultsMisoprostol was more effective than dinoprostone in causing cervical ripening (P= .01), inducing labor (P< .001), shortening the duration of labor (P< .001), and decreasing the need for oxytocin augmentation (P< .001). Nonreassuring fetal heart monitoring patterns associated with hyperstimulation were significantly more frequent (P< .001), and the incidence of cesarean deliveries because of this indication was significantly higher (P= .002) in patients receiving misoprostol.ConclusionsMisoprostol is an effective agent for cervical ripening and labor induction, but it causes an increase in cesarean deliveries associated with uterine hyperstimulation.