Physiologic and pharmacologic roles for prostaglandins in obstetrics.

Abstract

The biochemistry of prostaglandins is briefly summarized to give a foundation for this report on 2 potential areas in the field of prostaglandins and obstetrics: the physiology of parturition and the possible relation between prostaglandins and toxemia. Also reported is an update on the use of prostaglandins for labor induction. Prostaglandins are 20-carbon carboxylic acids that are formed enzymatically from polyunsaturated fatty acids (structural formulas are depicted and labeled with appropriate nomenclature). The physiology of parturition is gleaned basically from nonprimate studies but it seems evident that increasing uterine volume maintains a stimulation of uterine prostaglandin synthesis and release the oxytocin effects of which are kept in check by elevated levels of progesterone as gestation increases; hence the use of prostaglandin F2 alpha for labor induction has a physiological basis. In a double-blind study comparing oxytocin with prostaglandin however prostaglandin was found to be as effective as oxytocin but no more so. In addition the side effect of hypertonus occurred too frequently with prostaglandin induction leading this author to conclude that oxytocin is a better choice for labor induction. The relationship between prostaglandin and the renin-angiotensin system (i.e. its vasopressor role) is thought to explain to a degree the phenomenon of toxemia.