Aim: The aim of this paper was to establish the physiologic changes in the coagulation and fibrinolytic systems during normal pregnancy.
Methods: One-hundred and twenty normal pregnant women were investigated in a longitudinal study involving 3 measurements: blood samples were collected at 12, 24 and 36 weeks of gestation and were assayed for prothrombin time, antithrombin III (ATIII) activity, protein C activity, protein S (PS) activity, prothrombin fragments 1+2, type 1 plasminogen activator inhibitor activity, tissue plasminogen activator antigen, plasminogen, activated protein C resistance, factors VII and VIII levels and D dimer. Student t-test, one way analysis of variance (ANOVA) and Fisher test were used for statistical analysis.
Results: Factor VII and factor VIII were always increased with respect to controls. Variance analysis showed a statistically significant reduction for anticoagulants (PS) and a rise for F1+2 and D dimer. With regard to fibrinolysis, there was an increase both for t-PA and PA1-1 during pregnancy. Moreover, the increased activity of factors of haemostasis was accompanied by an increase of activity and concentration of ATIII and acquired activated protein C resistance.
Conclusions: These findings suggest that normal pregnancy is associated with an hypercoagulable state, resulting into a moderate risk for thrombosis during the different trimesters of pregnancy. Also broad spectrum assays which measure a range of trombin/fibrin formation in serum have become an established mean to identify activation of blood coagulation and/or fibrinolysis. There is a considerable interest in the application of these assays to the diagnosis of other acquired hypercoagulable states; such as thrombophilia during pregnancy. From the viewpoint of coagulation/fibrinolysis changes, the follow-up of thrombophilia markers could be recommended when levels of coagulation parameters exceed the normal values during pregnancy.