The effects of mifepristone on cervical ripening and labor induction in primigravidae.

OBJECTIVE

To compare the effects of 50 mg or 200 mg of oral mifepristone with placebo on cervical ripening and induction of labor in primigravid women at term with unfavorable cervices.

METHODS

This was a double-blind study in which 80 primigravidae at term with a modified Bishop score of 4 or less were randomly assigned to one of three treatment groups. They were assessed at 24-hour intervals for 72 hours, after which labor was induced if it had not occurred spontaneously.

RESULTS

Two hundred milligrams of mifepristone resulted in a favorable cervix (with a Bishop score greater than 6 or in spontaneous labor) in significantly more women than placebo (P = .01). An improvement in cervical ripening was seen in the group given 50 mg of mifepristone, but this was not statistically significant. There were more cesarean deliveries performed for fetal distress in the group treated with 200 mg of mifepristone than placebo, but this was not statistically significant and was not associated with any differences between groups in terms of neonatal outcome.

CONCLUSION

Mifepristone, a progesterone antagonist, is known to cause softening and dilation of the human early pregnant cervix and an increase in uterine activity. It is theoretically attractive for use as an adjunct in cervical priming and labor induction. In this study, 200 mg of mifepristone was significantly more likely to result in a favorable cervix than placebo.