Blood coagulation and idiopathic thromboembolism among fertile women.

A case-control study of fibrinolytic activity and antithrombin-III (AT-III) was conducted comparing 16 women within the childbearing ages who had a recent history of idiopathic thromboembolism to 29 age- and race-matched female controls without a history of thromboembolism. All subjects had stopped using oral contraceptives at least 12 months prior to study. No difference in AT-III was evident between cases and controls. The mean fibrinolytic response to venous occlusion in cases was significantly lower; however, baseline fibrinolysis was essentially identical. These data demonstrated a bimodal distribution of fibrinolytic response among controls. By dichotomizing fibrinolytic response between the two modes in the controls, we estimated that the rate of low fibrinolytic response was 6 times as frequent in cases as controls. Thus, low fibrinolytic response may signal a natural predisposition to thromboembolism which could be triggered by use of synthetic estrogens.