Whole blood platelet aggregation in normal pregnancy and pre-eclampsia

Platelet aggregation in whole blood in response to ADP, plasma beta-thromboglobulin (beta-TG) and thromboxane B₂ (TXB₂) levels, were evaluated in third-trimester patients with pre-eclanipsia (PE) (n==15) and in healthy third-trimester pregnant controls (n==43). 1 min after blood collection there was no difference in platelet response to ADP between PE and controls. Storage of blood unmasked hypoaggregability of platelets in PE implicating contribution of labile pro-aggregatory substance to ADP-induced aggregation tested at I min. Plasma TXB₂ in 10 controls (39.4 ± 8.7 pg/ml) was lower (p<0.05) than in 4 PE subjects (212.8 ± 130.0 pg/ml). Thus, seemingly normal aggregation of platelets to ADP in PE at I min after blood collection may be attributed to increased plasma level of TXA₂. Increased plasma level of beta-TG in PE (49.2 ± 7.0 ng/ml vs 27.3 ± 3.0 ng/ml; p<0.01) appears to be secondary to platelet consumption in which circulating TXA₂ may play a role.