Labor induction at term: a comparison of the effects of 50 microg and 25 microg vaginal misoprostol

PURPOSE OF INVESTIGATION: To compare the effects of 50 microg of vaginal misoprostol with 25 microg for labor induction at term. METHODS: One hundred and forty-seven pregnant women with indications for labor induction and cervical Bishop's score of < or = 6 were randomly assigned to receive either 50 microg (n = 74) or 25 microg (n = 73) of vaginal misoprostol every four hours until either a Bishop's score of > or = 8 or adequate uterine contraction frequency had been achieved. Induction-to-vaginal-delivery time was considered the primary outcome measure. RESULTS: Mean induction-to-vaginal-delivery time was significantly shorter in the 50-microg group than in the 25-microg group (526 +/- 141 min vs 745 +/- 218 min, respectively); oxytocin was administered to 65.8% of the patients in the 25-microg group and to 35.1% in the 50-microg group (p < .05). The incidence of tachysystole was significantly higher in the 50-microg group than in the 25-microg group (12% vs 2.7%, p < .05). We found no statistically significant difference between the two groups with respect to the rate of primary cesarean section, incidence of hyperstimulation syndrome, or neonatal outcome (p > .05). CONCLUSION: Fifty micrograms of vaginally administered misoprostol is an effective and inexpensive means of inducing labor at term. Uterine tachysystole may be associated more frequently with a 50-microg dose of vaginal misoprostol than with a 25-microg dose. Clinicians must accurately document the frequency and intensity of uterine contractions before every 50-microg dose of misoprostol is administered.