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

To compare the effects of 50 microg of vaginal misoprostol with 25 microg for labor induction at term.

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.

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).

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.