Mifepristone and misoprostol in the induction of labor at term.

OBJECTIVE: To assess the ability of mifepristone to prime the cervix adequately and induce labor in pregnant women at term; and when mifepristone alone proves insufficient, to determine whether oral misoprostol taken 48 h following mifepristone administration is effective in inducing labor.

METHODS: In this prospective study 50 pregnant women at term with an unfavorable cervix were given 400 mg of mifepristone orally and allowed to return home. If labor did not start within 48 h, the women were admitted and induction was continued with 50 mug of misoprostol, a prostaglandin (PG) E1 analogue, taken orally every 4 h. The 50 controls, who were matched prospectively for parity and pregnancy duration, underwent labor induction according to the routine administration of 3-mg tablets of PGE2 vaginally.

RESULTS: In the study group, 66% of the women entered labor spontaneously or had a sufficiently ripened cervix within 48 h of taking mifepristone. However, there was no difference in time between prostaglandin administration and delivery between the control group and the 34% of women who required misoprostol in the study group. In the study group, the cesarean section rate was significantly lower among the women whose labor was induced with mifepristone alone than among those who required misoprostol. There were no differences overall in obstetric or neonatal outcomes between the study and control groups.

CONCLUSIONS: In this pilot sample, 400 mg of mifepristone was effective in inducing cervical changes and labor. Although there were no adverse effects using oral misoprostol in combination with mifepristone, labor was more difficult to induce in the women who did not respond to mifepristone alone, and these women had a higher operative delivery rate.