HEMOSTATIC PARAMETERS AND PLATELET ACTIVATION BY FLOW-CYTOMETRY IN NORMAL-PREGNANCY - A LONGITUDINAL-STUDY

Nineteen pregnant women with uncomplicated pregnancies were studied du ring the first, second, and third trimesters. We measured the followin g hemostatic parameters: prothrombin time, activated partial thrombopl astin time, fibrinogen, antithrombin III, protein C, protein S, platel et number and volume. Platelet function was examined by a cytofluorime tric method, using an anti-GPM-140 antibody which is directed against a platelet alpha granule membrane protein. Activated platelets were ex pressed as a percentage of the GMP-140-positive platelets over total p latelets. Fibrinogen levels showed a steady increase during pregnancy; conversely prothrombin time, activated partial thromboplastin time, p rotein C, and antithrombin III showed no significant modifications and remained within the reference range. There was a decrease of protein S activity throughout pregnancy, although protein S antigen did not fo llow this trend. The decrease occurred early in pregnancy and persiste d during the second and third trimesters, reaching a stable plateau. W e observed no platelet volume change or activation: the percentage of activated platelets was within the normal reference range, even in lat e pregnancy.