A COMPARISON OF DIFFERING DOSING REGIMENS OF VAGINALLY ADMINISTERED MISOPROSTOL FOR PREINDUCTION CERVICAL RIPENING AND LABOR INDUCTION

OBJECTIVE: Our purpose was to compare two dosing regimens of vaginally administered misoprostol for preinduction cervical ripening and induc tion of labor. STUDY DESIGN: Five hundred twenty-two patients with ind ications for induction of labor and unfavorable cervices were randomly assigned to one of two dosing regimens of vaginally administered miso prostol. Twenty-five microgram tablets of misoprostol were placed in t he posterior vaginal fornix either every 3 hours to a maximum of eight doses or every 6 hours to a maximum of four doses. The maximal period of cervical ripening was 24 hours regardless of the number of misopro stol doses administered. Medication was not given after either spontan eous rupture of membranes or the beginning of active labor. RESULTS: A mong 522 patients enrolled, 261 were randomized to receive misoprostol every 3 hours and 261 to receive misoprostol every 6 hours. The avera ge interval from start of induction to vaginal delivery was shorter in the 3-hour dosing group (903.3 +/- 482.1 minutes) than in the 6-hour dosing group (1410.9 +/- 869.1 minutes) (p < 0.001). Oxytocin augmenta tion of labor occurred more commonly in the 6-hour dosing group (51.4% ) than in the 3-hour dosing group (41.8%) (p < 0.05). There were no si gnificant differences between routes of delivery. Overall, 108 patient s (20.8%) were delivered by cesarean section. There was a slightly hig her prevalence of tachysystole (six or more uterine contractions in a 10-minute window for two consecutive 10-minute periods) in the 3-hour group (14.6%) than in the 6-hour group (11.2%), but this difference wa s not statistically different. There were no significant differences i n the frequency of uterine hyperstimulation or hypertonus. There was n o significant difference between groups in the frequency of abnormal f etal heart rate tracings, meconium passage, 1- or 5-minute Apgar score s <7, neonatal resuscitations, or admissions to the neonatal intensive care unit. CONCLUSIONS: Vaginally administered misoprostol is an effe ctive agent for cervical ripening and induction of labor. Patients wit h the B-hour dosing schedule had longer intervals to delivery, more fr equently required oxytocin augmentation, and had more failed induction s than did patients with 3-hour dosing. Further investigation to chara cterize the safety of misoprostol is needed.