Induction of labor with mifepristone--a randomized, double-blind study versus placebo

To evaluate the efficacy of mifepristone in inducing labor in women with an unripe cervix, its effect on the cervix and on the status of the newborn.

In a prospective double-blind study, 36 post-term pregnant women with a Bishop score of 5 or less received either 400 mg mifepristone (n=24) or placebo (n=12). If, 48 hours after the treatment was started, labor had not begun or the Bishop score was 5 or less, the women were given 0.5 mg prostaglandin E2 intracervically, a treatment which was repeated 12 hours later, if necessary.

During the first 48 hours following treatment, 19 (79.2%) of the women treated with mifepristone and two of the women (16.7%) treated with placebo went into labor. In addition, one and three women, respectively, had a ripe cervix at the end of the 48h period. The overall success rate was thus 83.3% for mifepristone and 41.7% for placebo (p=0.008; OR 14.8; 95% CI 2.1-107.6). The median time from the start of treatment to delivery was also shorter (mifepristone 36h23' and placebo 53h17'). Treatment with intracervical PGE2 was needed more often after the placebo. The duration of labor, however, tended to be shorter after placebo than after mifepristone in the women who delivered vaginally. The frequencies of instrumental delivery were similar in both treatment groups. The median Apgar score was slightly lower at 1 minute (p<0.05) following mifepristone treatment, but did not differ at 5 and 10 minutes. There was no difference between the two treatment groups in the umbilical pH at delivery.

The results of the present study show that mifepristone is a simple and effective treatment for inducing labor in post-term women with an unripe cervix.