Changes in haemostasis during normal pregnancy

Abstract

Objectives: (1) To study the changes in the haemostatic variables during normal pregnancy, and (2) to compare them with the corresponding variables in a control group of nonpregnant women. Setting: University Hospital. Subjects: The study involves two groups of women: pregnant women (in 35th–40th gestational weeks (GW)) ( N = 35) and a control group of nonpregnant women ( N = 35). Methods: We examined the global tests, the variables relating to coagulation and fibrinolysis and the group of natural inhibitors of coagulation, and compared them between the two groups. Results: The pregnant women had statistically significantly higher values for: prothrombin time (PT) ( P < 0.0001), thrombin time (TT) ( P < 0.0001), fibrinogen ( P < 0.0001), activity of factor VII ( P < 0.0001), factor X ( P < 0.0001) and alpha2-antiplasmin ( P < 0.002), plasma concentration of d-dimer (plsDD) ( P < 0.0001) and activity of heparin cofactor II (HCII) ( P < 0.002). They had statistically significantly lower activity of protein C (PrC) ( P < 0.0001) and of total protein S (TPrS) ( P < 0.0001). Conclusion: During normal pregnancy the activation of coagulation is counterbalanced by the activation of fibrinolysis, which maintains the haemostatic balance.