Thromboembolic complications of oral contraceptive therapy.

During a ten-year period, 348 women were studied for a total of 5877 patient months for changes in hematologic parameters induced by oral contraceptives. Significant increases were observed in Factors I, II, VII, VIII, IX, X and plasminogen. Severe complications developed in four patients. All four had an abnormal blood coagulation profile, suggesting "hypercoagulability" before initiation of therapy. All four patients were of A or AB blood group. It appears from these data that hematologic workups may be useful in women who are about to embark on long-term oral contraceptive therapy.