Blood clotting activation during normal pregnancy

Pregnancy is considered as a hypercoagulable state (1) and an increased incidence of thromboembolic phenomena has been reported in pregnant women (2). Relevant changes in the hemostatic mechanism have been reported during physiological pregnancy: briefly, increased levels of coagulation factors, enhanced thrombin generation and suppression of fibrinolysis are commonly found in women with uncomplicated pregnancy (3-8). We recently described progressive increases in fibrinogen and D-dimer plasma levels during normal pregnancy (9). The increase in D-dimer levels makes difficult their interpretation for the exclusion of thromboembolic phenomena in pregnancy. The behavior of prothrombin fragment 1+2 (F1+2) levels during physiological pregnancy is scarcely known. The aim of this preliminary study was to establish range values of F1+2 plasma levels for different periods of normal pregnancy.