Changes in haemostasis during normal pregnancy

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.