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

Abstract

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.

PIP: 197 of the 214 women who presented to a Los Angeles, California (US), hospital in 1995-97 with spontaneous rupture of the membranes beyond 36 weeks' gestation (mean, 38 weeks) volunteered for a comparative study of the effectiveness of vaginally administered misoprostol and oxytocin infusion. Induction was started a minimum of 6 hours after the spontaneous rupture of membranes. In 98 women, 25 mcg of misoprostol (Cytotec) was placed in the posterior vaginal fornix and, if uterine contraction frequency was deemed inadequate, the dose was repeated once in the next 6 hours (average, 1.3 dose). In the remaining 99 women, oxytocin was administered by infusion pump according to standard protocol, for a maximum dose of 22 mU/minute. 75 (75.8%) of misoprostol-treated women and 73 (74.5%) of oxytocin-treated subjects were delivered vaginally within 24 hours of induction initiation. The mean time from start of induction to vaginal delivery was 811.5 +or- 511.4 minutes in the misoprostol group and 747.0 +or- 448.0 minutes in oxytocin-treated subjects. 85 (85.9%) misoprostol-treated women and 82 (83.7%) oxytocin-treated subjects delivered vaginally. There were no significant differences between treatment groups in terms of tachysystole or hypertonus incidence or in the frequency of abnormal fetal heart rate tracings. Chorioamnionitis was diagnosed in 28 (28.6%) misoprostol-treated and 26 (26.3%) oxytocin-treated subjects. Neonatal outcomes were similar in both groups. Although misoprostol administration did not reduce the cesarean section delivery rate, its efficacy and safety were similar to oxytocin's, indicating this is a suitable regimen in women with premature rupture of membranes beyond 36 weeks' gestation.