Induction of labour using prostaglandin pessaries of varying strength.

AN ideal method of induction of labour should be simple, safe, effective and noninvasive thereby increasing the acceptance by the patient and reducing the risks associated with amniotomy. The unripe cervix has always been a problem but in recent years prostaglandin E2 has been shown to have a direct effect on this, possibly by modifying the glyco-amnio glycans in the cervical ground substance. Over the past few years prostaglandin has been used with varying success rates by differing routes, however its use intravenously and orally has been limited by the side-effects of gastro-intestinal disturbance and local cellulitis at the venopuncture site. Prostaglandin has been administered as a jel extra-amniotically and as a pessary with encouraging results reported in the recent medical literature. Work from Queen Charlotte's Hospital by Shepherd et al. suggests that induction of labour using a 3 mg pessary can be a highly efficient and acceptable procedure. However, it was noted by these authors that a multiparous patient with a favourable cervix had vigorous uterine contractions upon insertion of the pessary. Uterine hypertonus had been noted by us in a higher percentage of cases while using a 3 mg pessary even when the cervix was not particularly favourable. Gordon-Wright and Elder have demonstrated that there is rapid systemic absorption of prostaglandin after administration of the drug in pessary form with a maximum effect in two hours and that the systemic level can remain high for up to six hours-this may explain the cases of hypertonus.