Objective: Our purpose was to compare the effect of vaginal administration of misoprostol (Cytotec) with that of dinoprostone (Cervidil) on cervical ripening and labor induction.
Study design: Two hundred patients with indications for induction of labor and unfavorable cervical examinations were randomly assigned to receive vaginally administered misoprostol (prostaglandin E1) or the dinoprostone (prostaglandin E2) vaginal insert. Twenty-five microgram tablets of misoprostol were placed in the posterior vaginal fornix every 4 hours for a maximum of six doses. Additional misoprostol was not given after either spontaneous rupture of membranes, adequate cervical ripening (Bishop score of > or = 8 or cervical dilatation of > or = 3 cm), or beginning of active labor. The vaginal insert, Cervidil, containing 10 mg of dinoprostone in a timed-release preparation was placed in the posterior vaginal formix for a maximum period of 24 hours. The vaginal insert was removed for spontaneous rupture of membranes, entry into active labor, adequate cervical ripening, or abnormality of uterine contractile pattern or fetal cardiac activity.
Results: Of the 200 patients enrolled, 99 were randomized to misoprostol and 101 to dinoprostone. The average interval from start of induction to vaginal delivery was 1 hour shorter in the misoprostol group (1296.7 +/- 722.1 minutes) than in the dinoprostone group (1360.0 +/- 792.0 minutes), but this difference was not statistically significant (p = 0.97). Oxytocin augmentation of labor was used in 50 (50.5%) misoprostol-treated patients and 43 (43.5%) dinoprostone-treated patients (relative risk 1.14, 95% confidence interval 0.86 to 1.51, p = 0.35). There were no significant differences between routes of delivery with misoprostol or dinoprostone. Overall, 38 patients (19.3%) had cesarean deliveries. There was a significantly lower prevalence of tachysystole (six or more uterine contractions in a 10-minute window for two consecutive 10-minute periods) in the misoprostol group (7.1%) than in the dinoprostone group (18.4%) (relative risk 0.52, 95% confidence interval 0.31 to 0.89, p = 0.02). There were no significant differences in frequency of uterine hyperstimulation or hypertonus. Abnormal fetal heart rate tracings were found in 23 (23.2%) of misoprostol-treated patients and 35 (35.7%) of dinoprostone-treated patients (relative risk 0.73, 95% confidence interval 0.52 to 1.01, p = 0.0546). No significant differences were found in meconium passage, 1- or 5-minute Apgar scores < 7, neonatal resuscitations, or admissions to the neonatal intensive care unit between the two groups.
Conclusions: Vaginally administered misoprostol is as effective as dinoprostone for cervical ripening and the induction of labor. Mean time intervals to delivery, need for oxytocin augmentation, and routes of delivery were similar between the two groups. Incidence of uterine tachysystole with misoprostol every 4 hours was significantly less than with dinoprostone.