Induction of labour is offered to pregnant women when it is thought the outcome will be better for the mother and/or baby if the baby is born than if the pregnancy continues. Common reasons include prolonged pregnancy, prelabour rupture of the membranes, concerns about the health of the mother such as pre-eclampsia or the baby such as poor growth. Prostaglandins are hormones, produced throughout the body and can be used to start (induce) labour. They are applied locally to the vagina as tablets, gels, suppositories and pessaries to reduce side-effects. The dose, number of doses, and time between doses vary considerably. Sustained release pessaries reduce the need for repeat doses and so the number of vaginal examinations.
This review set out to determine the effectiveness and safety of vaginal prostaglandins for third trimester cervical ripening and induction of labour (the cervix softens, shortens and opens, the uterus starts to contract regularly). Eight different comparisons were made, different vaginal prostaglandins were compared with placebos or no treatment, or other vaginal prostaglandins (PGE2, PGF2a, except misoprostol) and different preparations and dosages were compared. We identified 70 studies involving a total of 11,487 women. Vaginal prostaglandins increase the likelihood of vaginal birth within 24 hours, but they can also stimulate the uterus to contract too much and this may cause the baby's heart to slow, however they did not increase the caesarean section rate and may reduce it. Overall, the trials do not show any effect (improvement or worsening) of many important outcomes. Prostaglandin E2 tablets, gels, or pessaries including sustained release preparations appear to be as good as each other or the differences between them are small and have not yet been detected in the trials. Lower-dose regimens, as defined in the review, appeared to be as good as higher-dose regimens (eight trials, 1615 women).
Very limited data were available in the included trials on time in labour and patient satisfaction. Few studies have addressed issues relating to the safety of using vaginal prostaglandins for induction of labour as outpatients.