Prostaglandins in obstetrics and gynaecology.

THE first reports of the use of the natural prostaglandins in the field of obstetrics and gynaecology appeared in 1968, initially for the induction of term labour in patients with fetal death and subsequently for patients with a live fetus. Since then numerous clinical reports have described the efficacy of using prostaglandins for this purpose administered by a variety of different routes and also for other indications particularly the induction of pre-term labour and for termination of pregnancy. In physiological terms, the role of prostaglandins in the functions that this speciality covers, e.g. fallopian tube and spermatozoal motility, ovulation, conception, corpus luteal development, and myometrial contractility, remains inconclusive since there appear to be important differences between members of various animal species and the human female. Earlier problems with assaying the natural prostaglandins led to differences of opinion as to whether, for example, circulating prostaglandins increased during pregnancy and labour, and whether their release was possibly associated with the initiation and maintenance of the latter process. Peripheral blood sampling has failed to confirm any such definite association but that does not imply that subtle and possibly transient changes do not occur in the feto-placental unit, since it has been suggested that the more stable prostaglandin metabolites increase in liquor during late pregnancy and indeed during labour, and that prostaglandin levels are higher in the feto-placental unit than in the mother. Results of tests in circulating natural prostaglandin levels performed in the Institute of Obstetrics and Gynaecology do not indicate a surge immediately preceding the onset of labour as has been described in the sheep, but rather a peak occurring at about 36 weeks with a subsequent fall. With regard to corpus luteal function there is evidence in some animals that prostaglandins are luteolytic. However, prostaglandins do not appear to be luteolytic in the human female with doses that are clinically tolerable. The