Thrombosis Prediction Based on Reference Ranges of Coagulation-Related Markers in Different Stages of Pregnancy

Introduction: Careful monitoring of the hypercoagulable state is required during pregnancy. However, coagulation and fibrinolysis markers are not fully utilized because there are no reference values reflective of coagulation and fibrinolysis dynamics during pregnancy, which differ from the nonpregnant state. Methods: Changes in antithrombin (AT), fibrinogen (Fbg), prothrombin fragment 1+2 (F1+2), thrombin–antithrombin complex (TAT), soluble fibrin (SF), D-dimer (DD), and protein S (PS) were investigated in healthy pregnant women, and reference ranges in the early, mid, late, and end stages of pregnancy were established. Results: The AT was essentially constant throughout pregnancy. The Fbg, F1+2, TAT, and DD increased significantly as pregnancy progressed. In contrast, SF did not show a significant increase throughout the entire pregnancy period. Total PS antigen and total PS activity showed a corresponding decrease from early gestation. When test data in 3 cases in which deep vein thrombosis or intrauterine fetal death occurred during pregnancy were compared to the established reference ranges, all of the cases had multiple markers with values that exceeded the reference ranges. Conclusion: Establishing reference ranges for each week could potentially make it possible to evaluate abnormalities of the coagulation and fibrinolysis systems during pregnancy. Of note, SF might be a useful marker that reflects thrombus formation during pregnancy. Larger-scale studies will be required to establish reference ranges for every gestational week.