Haemostatic and rheological changes in normal pregnancy and pre-eclampsia.

Platelet activity (microaggregate formation, ADP-aggregation and beta-thromboglobulin release), coagulation activity (fibrinogen level and factor VIII related antigen/coagulant activity), and rheological factors (plasma viscosity, whole-blood viscosity and erythrocyte deformability) were studied serially in 14 healthy pregnancies to determine the effect of gestational age. Fourteen patients with pre-eclampsia, each matched for stage of gestation with a normal pregnancy, showed normal rheology of circulating blood and normal aggregability of circulating platelets, but there was a significant increase in platelet release of beta-thromboglobulin and a shorter platelet production time, indicating a shorter life-span. The results suggest that localized platelet activation within the utero-placental microvasculature, rather than a rheological abnormality, is a likely contributory factor to the occlusive vascular lesion of pre-eclampsia and fetal growth retardation.