The effect of vaginal pH on the efficacy of vaginal misoprostol for induction of labor

Abstract

Misoprostol was reported to be an effective agent for cervical ripening and induction of labor. Our purpose was to evaluate whether vaginal pH affected the efficacy of misoprostol for induction of labor. The vaginal pH of 103 women admitted for induction of labor were measured. According to the vaginal pH, two groups were generated, those with a vaginal pH <5 (n= 65), and those with a vaginal pH > or =5 (n=38). All women received intravaginal misoprostol tablets, 50 microg every 4 hours up to three doses. Further medication was not given after entry into active labor or spontaneous rupture of membranes. In cases of failed induction or arrest disorders oxytocin augmentation was used. The average interval from start of induction to vaginal delivery was shorter, and oxytocin augmentation was required less commonly in the lower pH group. We did not find any significant difference in cesarean section rates, or incidence of adverse maternal or fetal outcome. Vaginal pH may affect the pharmacokinetics of vaginally administered misoprostol, and may cause an alteration in induction to delivery interval.