Eicosanoids and preterm labour

Abstract

Products of arachidonic acid metabolism (eicosanoids, e.g. some prostaglandins and leukotrienes) have important roles in the maintenance of pregnancy, and certain diseases of pregnancy such as pregnancy-induced hypertension and the machanism(s) of parturition both at term and before term. The volume of literature describing these last relationships dictates that the present review has to be focused rather than global in nature. Only studies of preterm labour in women and the use of human tissues will be discussed in detail despite the limitations in experimental designs that are imposed on such studies. Emphasis will be placed on studies of cyclo-oxygenase and to a lesser extant lipoxygenase pathways of arachidonic acid metabolism mentioning only briefly the pathways for catabolism of these eicosanoids. It should be noted also that eicosanoids from the epoxygenase pathways and those not derived from arachidonic acid will not be discussed here. The review of literature will not be comprehensive but rather selective in order to focus on specific issues of importance or controversy. In developing concepts of regulation I have emphasized studies with amnion since this tissue has received most attention experimentally. The significance of the eicosanoids in the mechanisms of labour at term and before will be described primarily in a section in which I have attempted to deleneate those regulatory mechanisms that are considered most significant in, or specific to, pregnancy and parturition. Studies of labour at term will be freely interspersed with studies specific to preterm labour since the latter are limited, and we need a ‘strandard’ for comparison; moreover, results from one series of studies helps the development of concepts for the other. Finally, the reader is directed to several excellent reviews that concentrate on areas not emphasized in this review.1–7