ObjectiveTo compare the efficacy and vaginal birth intervals after intravaginal or oral misoprostol for labor induction.MethodsOne hundred seventy-eight women were randomized to one of two double-blind groups: 1) oral misoprostol 200 μg and one-half tablet placebo intravaginal or 2) oral placebo tablet and one-half tablet of a 100-μg misoprostol intravaginal (dose 50 μg). Doses were repeated every 6 hours until labor was established (maximum of three doses).ResultsNinety-three subjects were assigned to oral misoprostol and 85 to intravaginal administration. Oral administration was accompanied by significantly shorter intervals to the onset of uterine contractility (133 ± 78 minutes versus 168 ± 93,P< .01) but a higher incidence of abnormal uterine contractile activity (tachysystole 38.7% versus 20.0%,P< .01; hyperstimulation syndrome 44.1% versus 21.2%,P< .01). No adverse maternal or neonatal outcomes were noted, nor were there differences in cesarean delivery rates or total lengths of labor.ConclusionOral administration of 200 μg misoprostol has similar efficacy to intravaginal administration of 50 μg but is associated with more frequent abnormal uterine contractility.