Oral contraceptives and venous thromboembolism.

In 58 patients with phlebographically diagnosed deep vein thrombosis during oral contraception the extension and localization of the thrombotic process was analysed in relation to the coagulation and fibrinolytic system 6 months after thrombosis. Left-sided thrombi dominated and the thrombi were more extensive and proximal on the left side. This left-sided dominance was more apparent with higher oestrogen content in the pills. The right-sided thrombi more often were the source of pulmonary embolism. In 31% of the patients a defective fibrinolytic system was found; this defect was seen more often in patients with right-sided thrombi. Only very few defects were found in the coagulation system. No patients had an antithrombin III deficiency.