Oral misoprostol for induction of labour

Oral misoprostol is effective at inducing (starting) labour. It is more effective than placebo, as effective as vaginal misoprostol and results in fewer caesarean sections than vaginal dinoprostone or oxytocin. However, there are still not enough data from randomised controlled trials to determine the best dose to ensure safety.

Induction of labour in late pregnancy is used to prevent complications when the pregnant woman or her unborn child are at risk. Reasons for induction include being overdue, pre-labour rupture of membranes and high blood pressure. Prostaglandins are hormones that are naturally present in the uterus (womb); they soften the cervix and stimulate contractions in labour. The artificial prostaglandin E2 dinoprostone can be administered vaginally to induce labour but it is unstable at room temperature and is expensive. Oral misoprostol is a cheap and heat stable prostaglandin E1 synthetic analogue originally developed for the treatment of stomach ulcers.

This review of 76 randomised controlled trials (14,412 women) found that oral misoprostol appears to be at least as effective as current methods of induction. Nine trials (1,282 women) showed that oral misoprostol was equivalent to intravenous infusion of oxytocin, but resulted in significantly less caesarean sections. A higher rate of meconium staining of the amniotic fluid was not associated with any adverse effect on the unborn baby and could be a direct effect of the misoprostol on the baby's gut. This effect was also seen in the comparison with vaginal misoprostol but appeared to be less. The 37 thirty seven trials (6,417 women) that compared oral and vaginal misoprostol reported similar effectiveness but those taking oral misoprostol had better neonatal condition at birth and less postpartum haemorrhage.

In 12 twelve trials (3,859 women) comparing oral misoprostol with vaginal dinoprostone, women given misoprostol were less likely to need caesarean section (21% compared with 26% of women), although the induction may have been slower overall. The most common dose of misoprostol in these studies was 20 mcg. The rates of hyperstimulation and meconium staining were similar with misoprostol and dinoprostone.

The nine trials that compared oral misoprostol with placebo (1,109 women) showed that oral misoprostol is more effective than placebo for inducing labour, with a lower caesarean section rate and fewer admissions to neonatal intensive care unit. The quality of evidence for some comparisons was very robust (for example, oral misoprostol versus vaginal misoprostol) but the strength of recommendations was less for other comparisons.

Authors' conclusions: 

Oral misoprostol as an induction agent is effective at achieving vaginal birth. It is more effective than placebo, as effective as vaginal misoprostol and results in fewer caesarean sections than vaginal dinoprostone or oxytocin.

Where misoprostol remains unlicensed for the induction of labour, many practitioners will prefer to use a licensed product like dinoprostone. If using oral misoprostol, the evidence suggests that the dose should be 20 to 25 mcg in solution. Given that safety is the primary concern, the evidence supports the use of oral regimens over vaginal regimens. This is especially important in situations where the risk of ascending infection is high and the lack of staff means that women cannot be intensely monitored.

Read the full abstract...
Background: 

Misoprostol is an orally active prostaglandin. In most countries misoprostol is not licensed for labour induction, but its use is common because it is cheap and heat stable.

Objectives: 

To assess the use of oral misoprostol for labour induction in women with a viable fetus.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (17 January 2014).

Selection criteria: 

Randomised trials comparing oral misoprostol versus placebo or other methods, given to women with a viable fetus for labour induction.

Data collection and analysis: 

Two review authors independently assessed trial data, using centrally-designed data sheets.

Main results: 

Overall there were 76 trials (14,412) women) which were of mixed quality.

In nine trials comparing oral misoprostol with placebo (1109 women), women using oral misoprostol were more likely to give birth vaginally within 24 hours (risk ratio (RR) 0.16, 95% confidence interval (CI) 0.05 to 0.49; one trial; 96 women), need less oxytocin (RR 0.42, 95% CI 0.37 to 0.49; seven trials; 933 women) and have a lower caesarean section rate (RR 0.72, 95% CI 0.54 to 0.95; eight trials; 1029 women).

In 12 trials comparing oral misoprostol with vaginal dinoprostone (3859 women), women given oral misoprostol were less likely to need a caesarean section (RR 0.88, 95% CI 0.78 to 0.99; 11 trials; 3592 women). There was some evidence that they had slower inductions, but there were no other statistically significant differences.

Nine trials (1282 women) compared oral misoprostol with intravenous oxytocin. The caesarean section rate was significantly lower in women who received oral misoprostol (RR 0.77, 95% CI 0.60 to 0.98; nine trials; 1282 women), but they had increased rates of meconium-stained liquor (RR 1.65, 95% CI 1.04 to 2.60; seven trials; 1172 women).

Thirty-seven trials (6417 women) compared oral and vaginal misoprostol and found no statistically significant difference in the primary outcomes of serious neonatal morbidity/death or serious maternal morbidity or death. The results for vaginal birth not achieved in 24 hours, uterine hyperstimulation with fetal heart rate (FHR) changes, and caesarean section were highly heterogenous - for uterine hyperstimulation with FHR changes this was related to dosage with lower rates in those with lower doses of oral misoprostol. However, there were fewer babies born with a low Apgar score in the oral group (RR 0.60, 95% CI 0.44 to 0.82; 19 trials; 4009 babies) and a decrease in postpartum haemorrhage (RR 0.57, 95% CI 0.34 to 0.95; 10 trials; 1478 women). However, the oral misoprostol group had an increase in meconium-stained liquor (RR 1.22, 95% CI 1.03 to 1.44; 24 trials; 3634 women).

Share/Save