Misoprostol is more efficacious for labor induction than prostaglandin E2, but is it associated with more risk?

Our purpose was to compare the efficacy and safety of misoprostol with dinoprostone (Prepidil) for labor induction.

In a randomized, controlled trial of labor induction, patients were randomly assigned to receive either 50 microgram of intravaginal misoprostol every 4 hours or 0.5 mg of intracervical prostaglandin E2 every 6 hours. Eligibility criteria included gestation of >/=31 weeks, Bishop score <6, and fewer than 12 contractions per hour. Primary outcomes were cesarean section, induction to delivery time, oxytocin use, and fetal distress requiring delivery.

One hundred fifty-nine women were randomly assigned to receive misoprostol (n = 81) or Prepidil (n = 78). There were no differences in the indication for induction, preinduction Bishop score, epidural use, or cesarean section rate. Mean time to delivery was significantly shorter in the misoprostol group (19 hours 50 minutes) than in the Prepidil group (28 hours 52 minutes) (P =.005). Only 58% of women in the misoprostol group required oxytocin augmentation, in comparison with 88% of women receiving Prepidil (P =.00002). However, 41% of women receiving misoprostol and 17% receiving Prepidil had late decelerations or bradycardias (P =.001), and 20% of the misoprostol group and 5% of the Prepidil group had deliveries for fetal distress (P =.05).

Misoprostol is more efficacious than Prepidil for labor induction. However, the significantly increased incidence of abnormal fetal heart rate tracings and the trend in increased deliveries for fetal distress with misoprostol dosing of 50 microgram every 4 hours are of concern. These data suggest that either a lower dose of misoprostol or less frequent dosing of misoprostol should be considered.