BACKGROUND

Misoprostol is a synthetic prostaglandin which has been used to induce labour. Oral use of the drug misoprostol may be convenient, but an overdose could cause uterine hyperstimulation and precipitate labour which may be life-threatening for both mother and fetus.

OBJECTIVES

The objective of this review was to assess the effects of oral misoprostol used for labour induction in women with a viable fetus.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register were searched in May 2000.

SELECTION CRITERIA

Randomised trials of oral misoprostol versus other methods, placebo or no treatment given to women with a viable fetus for labour induction.

DATA COLLECTION AND ANALYSIS

This is one of a series of the Cochrane reviews of methods of cervical ripening and labour induction using standardised methodology. The Cochrane Pregnancy and Childbirth Group has developed a strategy to deal with the large volume and complexity of trial data related to labour induction. Data from all relevant trials are extracted centrally. They are incorporated into a series of primary reviews arranged by methods of induction of labour. The data from the primary reviews will be incorporated into secondary reviews. The secondary reviews are arranged by category of woman according to parity, membrane status and previous caesarean section. To avoid duplication of data in the primary reviews, the labour induction methods have been listed in a specific, hierarchical order. This review includes comparisons between oral misoprostol with only those methods above it on the list (placebo, vaginal prostaglandins, intracervical prostaglandins, oxytocin, amniotomy, oxytocin and amniotomy or vaginal misoprostol).

MAIN RESULTS

One trial with 80 randomised women with prelabour rupture of membranes at term showed that, compared with placebo, oral misoprostol reduces the need for oxytocin infusion from 51 percent to 13 percent (relative risk 0.25, 95% confidence interval 0.1 to 0.6) and shortens delivery time by 8.7 hours (95% CI 6.0 to 11.3). Compared with vaginal prostaglandins, oral misoprostol showed no beneficial or harmful effects. However, only two trials were included with 957 randomised women in total. In six trials with 1042 randomised women that compared oral with vaginal misoprostol, oral misoprostol appeared to be less effective. More women in the oral misoprostol group did not achieve vaginal delivery within 24 hours of randomisation (54.2%) compared with 35.2% in the vaginal misoprostol group (relative risk 1.55, 95% confidence intervals 1.30 to 1.85). Caesarean section rate was 17.7% in the oral misoprostol group compared with 21.7% in the vaginal misoprostol group (relative risk 0.82, 95% confidence intervals 0.64 to 1.05). There was no difference in uterine hyperstimulation with fetal heart rate changes (9.5% versus 9.9%; relative risk 0.93, 95% confidence intervals 0.66 to 1.33). There were no reported cases of severe neonatal and maternal morbidity.

REVIEWER'S CONCLUSIONS: Oral misoprostol may be an effective method for labour induction. However, the data on safety are lacking. It is possible that clinically effective oral regimens may have an unacceptably high incidence of complications such as uterine hyperstimulation and possibly uterine rupture.