Oral Misoprostol for Labor Augmentation

Abstract

In addition to artificial rupture of the membranes, intravenous oxytocin is essentially the sole medication for labor augmentation in the United States. Although misoprostol has been shown in numerous trials to be an effective agent for labor induction, there have been concerns with respect to its uterotonic properties and relatively long half-life, when used as a contractile agent for women in spontaneous labor who require augmentation. Limited data are available on the use of oral misoprostol as an augmentation agent. The aim of this randomized controlled trial was to compare the efficacy of oral misoprostol and intravenous oxytocin among women in spontaneous active labor who require augmentation. A total of 350 singleton women with spontaneous labor and cervical dilation between 4 and 8 cm were randomized to either oral misoprostol (n = 376) or intravenous oxytocin (n = 374). The main study outcome was the incidence of uterine tachysystole, hypertonus, or both. Secondary outcomes assessed included mode of delivery, duration of labor, presence of nonreassuring fetal heart rate, and selected maternal and neonatal outcomes. The admission-to-study drug interval was significantly shorter among women in the misoprostol group (330 minutes, range: 252–408) compared with those in the oxytocin group (402 minutes, range: 330–492; P < 0.001). However, no significant difference was found in the interval between initiation of the study drug and delivery (306 minutes in the misoprostol group vs. 276 minutes in the oxytocin group; P = 0.29). The incidence of uterine tachysystole, hypertonus, or both was higher in the misoprostol group (76%) compared with the oxytocin group (64%); P = 0.02. However, this increase appeared to be secondary to uterine hypertonus, as there was no difference between groups in the incidence of tachysystole (P = 0.74). There was no increased likelihood that women in the misoprostol group would experience a nonreassuring fetal heart rate or require a cesarean delivery (P = 0.20 and P = 0.78, respectively). No significant differences were noted between the groups in maternal or neonatal outcomes. The authors conclude that these findings suggest that oral misoprostol may be effective for augmentation of labor.