Mifepristone for induction of labour

Abstract

Background: The steroid hormone, progesterone, inhibits contractions of the uterus. Antiprogestins (including mifepristone) have been developed to antagonise the action of progesterone, and these have a recognised role in medical termination of early or mid-pregnancy. Animal studies have suggested that mifepristone may also have a role in inducing labour in late pregnancy.

Objectives: To determine the effects of mifepristone for third trimester cervical ripening or induction of labour.

Search strategy: We searched the Cochrane Pregnancy and Childbirth Group trials register, the Cochrane Controlled Trials Register, and reference lists of relevant papers.

Selection criteria: Selection criteria included: (1) clinical trials comparing mifepristone used for third trimester cervical ripening or labour induction with placebo/no treatment or other labour induction methods; (2) random allocation to the treatment or control group; (3) adequate allocation concealment; (4) violations of allocated management not sufficient to materially affect conclusions; (5) clinically meaningful outcome measures reported; (6) data available for analysis according to the random allocation; (7) missing data insufficient to materially affect the conclusions.

Data collection and analysis: This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology. Data were extracted by the reviewer and, independently, by a colleague.

Main results: Seven trials, that recruited 594 women, are included. All trials compared mifepristone with placebo, except for one that compared mifepristone with no treatment. Compared to placebo, mifepristone treated women were less likely to have an unfavourable cervix at 48 hours (relative risk [RR] 0.36, 95% confidence intervals [CI] 0.2-0.63) or 96 hours (RR 0.39, 95% CI 0.23-0.66). Mifepristone treated women were more likely to have delivered within 48 and 96 hours of treatment than were placebo treated/no treatment women - 48 hours: RR 2.82, 95% CI 1.82-4.36; 96 hours: RR 3.40, 95% CI 1.96-5.92. Mifepristone treated women were less likely to undergo caesarean section (RR 0.71, 95% CI 0.53-0.95). There is little information about fetal outcome, although there was no evidence that neonatal hypoglycaemia might be more common after exposure to mifepristone. Similarly, there is little information about maternal side-effects although some nausea and vomiting was reported in one trial.

Reviewer's conclusions: There is insufficient information available from clinical trials to support the use of mifepristone to induce labour. However, available data do show that mifepristone is better than placebo at ripening the cervix, and inducing labour. There is evidence of a possible reduction in the incidence of caesarean section following mifepristone treatment (compared to placebo) that would justify further trials. We found no trials that compared mifepristone with alternative methods of inducing labour e.g. prostaglandins.