Induction of labor with misoprostol for premature rupture of membranes beyond thirty-six weeks' gestation.

OBJECTIVE: Our purpose was to compare vaginally administered misoprostol (Cytotec) with intravenous oxytocin for labor induction in women with premature rupture of membranes beyond 36 weeks' gestation.

STUDY DESIGN: Two hundred subjects with rupture of membranes without labor were randomly assigned to receive vaginally administered misoprostol or intravenous oxytocin. Twenty-five micrograms of misoprostol (Cytotec) was placed in the posterior vaginal fornix. If cervical ripening (Bishop score of > or = 8 or cervical dilatation of > or = 3 cm) or active labor did not occur, a single repeat dose of misoprostol was given 6 hours later. Oxytocin was administered intravenously by a standardized incremental infusion protocol to a maximum dose of 22 mU per minute.

RESULTS: Of the 197 subjects evaluated, 98 received misoprostol and 99 oxytocin. The average interval from start of induction to vaginal delivery was about 1 hour longer in the misoprostol group (811.5 +/- 511.4 minutes) than in the oxytocin group (747.0 +/- 448.0 minutes) (P = .65, log transformed data). Oxytocin administration was necessary in 37 of 98 (37.8%) of misoprostol-treated subjects. Vaginal delivery occurred in 85 misoprostol-treated subjects (86.7%) and 82 (85.9%) oxytocin-treated subjects (relative risk 1.17, 95% confidence interval 0.78 to 1.78, P = .45) with the remainder undergoing cesarean birth. There was no difference in the incidence of tachysystole (six or more uterine contractions in a 10-minute window for two consecutive 10-minute periods) or hypertonus between the two groups. There was no significant difference in frequency of abnormal fetal heart rate tracings between the two groups (29.6% in the misoprostol group and 28.9% in the oxytocin group, P = .91). Chorioamnionitis was diagnosed in 28 (28.6%) misoprostol-treated subjects and 26 (26.3%) oxytocin-treated subjects (P = .72, relative risk 1.06, 95% confidence interval 0.78 to 1.45). No significant differences were found in the incidence of fetal meconium (8.1% and 9.1%), 1- or 5-minute Apgar scores < 7 (11.0% and 10.2% of 1-minute Apgar scores, and 2.0% and 2.0% of 5-minute Apgar scores), neonatal resuscitation (24.5% and 27.6%), or admission to the neonatal intensive care unit (25.5% and 32.3%) between the two groups.

CONCLUSIONS: Vaginal administration of misoprostol (Cytotec) is an effective alternative to oxytocin infusion for labor induction in women with premature rupture of the membranes near term. The incidence of untoward effects is similar with use of the two agents.