The unripe cervix and its management for labour induction.

Cervical state plays an important part in the outcome of induced labour. The mechanism governing the process of ripening, which is part of the continuum ending in labour, is still not fully understood, but is thought to involve several hormonal interactions including oestrogens, progesterone, and prostaglandins. The prostaglandins have been found to produce the best results for inducing labour when the cervix is unripe and are most effective when administered locally and most convenient when placed in the vagina as a viscous gel, wax pessary or slow release pessary. They are of benefit for labour induction in cases previously delivered by lower segment caesarean section, breech presentation, and multiple pregnancies. Hyperstimulation and fetal distress may occur and this might be reduced with the use of the controlled release hydrogel pessary. Newer approaches using an antiprogestin or recombinant relaxin are being explored in the hope that further improvements in outcome can be obtained.