Oral misoprostol for induction of labour

Abstract

Background: Prostaglandins are hormones naturally present in the uterus that cause contractions during labour. A synthetic prostaglandin analogue misoprostol is produced in tablets that can be given orally or vaginally, but it is not yet licensed for use in pregnancy. Unlicensed use of misoprostol in pregnancy is increasingly common, because misoprostol is cheap, stable at room temperature and effective in causing uterine contractions. Oral use of the drug misoprostol may be convenient, but high doses could cause uterine hyperstimulation and uterine rupture 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 in the third trimester of pregnancy.

Search strategy: The Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register were searched in December 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. This review includes comparisons between oral misoprostol with placebo, vaginal prostaglandins, intracervical prostaglandins, oxytocin, amniotomy, oxytocin and amniotomy or vaginal misoprostol. Data from all relevant trials are extracted by the reviewer using centrally designed data sheets.

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 (CI) 0.1 to 0.6) and shortens delivery time by 8.7 hours (95% CI 6.0 to 11.3). Compared with vaginal or intracervical prostaglandins, oral misoprostol showed no beneficial or harmful effects. However, only two trials with 962 randomised women in total compared oral misoprostol with vaginal dinoprostone and one trial with 200 women compared oral misoprostol with intracervical dinoprostone. Two small trials with 188 women in total compared oral misoprostol and oxytocin in women with term ruptured membranes and found no significant differences in prespecified outcomes. In seven trials with 1278 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 (50%) compared with 39.7% in the vaginal misoprostol group (relative risk 1.27, 95% confidence intervals 1.09 to 1.47). The caesarean section rate was lower in the oral misoprostol group (16.7%) compared with 21.7% in the vaginal misoprostol group (relative risk 0.77, 95% confidence intervals 0.61 to 0.97). There was no difference in uterine hyperstimulation with fetal heart rate changes (8.5% versus 7.4%; relative risk 1.11, 95% confidence intervals 0.78 to 1.59). There were no reported cases of severe neonatal and maternal morbidity.

Reviewer's conclusions: Oral misoprostol is an effective method for labour induction in the third trimester. However, the data on optimal regimens and safety are lacking. It is possible that effective oral regimens may have an unacceptably high incidence of complications such as uterine hyperstimulation and possibly uterine rupture.