[Significance of prostaglandins and other eicosanoids in the physiology and physiopathology of pregnancy].

Numerous investigations in animals and humans on the role of eicosanoids in pregnancy yielded the following results. During normal pregnancy, there is an increased production of eicosanoids with a vasodilatory action, prostaglandin E2 (PGE2) and prostacyclin (PGI2), especially in the uteroplacental and renal regions. This additional production contributes to a reduction in peripheral resistance so that the increase of blood volume which is specific for pregnancy can occur without increase in blood pressure. The fact that eicosanoids participate in this mechanism is shown by administration of prostaglandin synthesis inhibitors, thus producing a rise in blood pressure. In the autoregulation of the vessels, interactions between renin angiotensin and PGE2 and PGI2 are thought to play an important role also in pregnancy. In support of this concept it has been shown that the pregnancy-specific reduction in vasoconstrictor action of angiotensin, is abolished when prostaglandin synthesis inhibitors are given. It is assumed that PGE2/PGI2 production and the renin angiotensin production influence each other physiologically. Another important factor in the control of the haemodynamics and blood coagulation is represented by the prostacyclin-thromboxane system. In normal pregnancy there should be a production equilibrium between the two antagonistic eicosanoids. In preeclampsia this equilibrium, which is particularly marked in the placenta and region of the foetal vessels, is disturbed with decreasing PGI2. The main symptoms of preeclampsia--increase in blood pressure, coagulation disturbances and diminished placental circulation--can be derived from this. In diabetes and foetal growth retardation, both of which predispose to preeclampsia, similar changes in eicosanoid production have been observed. Hence, in case of preeclampsia with disturbed eicosanoid production the administration of prostaglandin synthesis inhibitors such as peripherally acting analgesics and corticoids is contraindicated. Approaches to a rational therapy such as administration of thromboxane synthesis inhibitors, a diet with prostaglandin precursors and infusions of PGI2 appear promising according to preliminary results. Further advances may be expected after the function of eicosanoids of the lipoxygenase paths in preeclampsia has been elucidated.