Abstract
Since the first reports of the efficacy of locally administered prostaglandin E2 in ripening the cervix before induction of labour (Calder et al, 1977; Mackenzie et al, 1977), extra-amniotic and vaginal routes of administration (Toplis et al, 1979) and different prostaglandins and doses (Mackenzie et al., 1979) have been compared. We have found no reports dealing with duration of exposure of the cervix to prostaglandin E2.