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 mifeprist one with placebo on cervical ripening and induction of labor in primig ravid women at term with unfavorable cervices. Methods: This was a dou ble-blind study in which 80 primigravidae at term with a modified Bish op 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 w hich 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 signif icantly more women than placebo (P = .01), An improvement in cervical ripening was seen in the group given 50 mg of mifepristone, but this w as not statistically significant, There were more cesarean deliveries performed for fetal distress in the group treated with 200 mg of mifep ristone than placebo, but this was not statistically significant and w as not associated with any differences between groups in terms of neon atal outcome. Conclusion: Mifepristone, a progesterone antagonist, is known to cause softening and dilation of the human early pregnant cerv ix and an increase in uterine activity. It is theoretically attractive for use as an adjunct in cervical priming and labor induction. In thi s study, 200 mg of mifepristone was significantly more likely to resul t in a favorable cervix than placebo. (Obstet Gynecol 1998;92: 804-9. (C) 1998 by The American College of Obstetricians and Gynecologists,)