A Cochrane review included 121 studies. Compared to placebo, misoprostol (a prostaglandin E1 analogue) was associated with reduced failure to achieve vaginal delivery within 24 hours (RR 0.51, 95% CI 0.37 to 0.71). Uterine hyperstimulation, without fetal heart rate changes, was increased (RR 3.52, 95% CI 1.78 to 6.99). Compared with vaginal prostaglandin E2, intracervical prostaglandin E2 and oxytocin, vaginal misoprostol was associated with less epidural analgesia use, fewer failures to achieve vaginal delivery within 24 hours and more uterine hyperstimulation. Compared with vaginal or intracervical prostaglandin E2, oxytocin augmentation was less common with misoprostol and meconium-stained liquor more common. Lower doses of misoprostol compared to higher doses were associated with more need for oxytocin augmentation and less uterine hyperstimulation, with and without fetal heart rate changes. No information on women's views was found.
Authors' comment: The studies reviewed were not large enough to exclude the possibility of rare but serious adverse events, particularly uterine rupture. Another Cochrane review has shown that the oral route of administration is preferable to the vaginal route; oral route is associated with considerably less uterine hyperstimulation with fetal heart rate changes.