[Oral contraception and menopausal hormone replacement: effects on hemostasis and risk of venous thromboembolism].

The estrogen component of oral contraceptives enhances both coagulation and fibrinolysis. These contradictory effects result in activation of coagulation and an increased risk of venous thromboembolism. The relative risk is about 4-fold as compared with a nonuser of the same age. However, the risk of deep vein thrombosis or pulmonary embolism attributable to the pill is small (2 cases per 10,000 users per year). Pills containing a progestagen of the so-called 3rd generation seem to increase the risk by an additional factor of 2. Though small, the risk of venous thromboembolism makes it necessary before any oral contraceptive prescription to take a thorough personal and family history (including risk factors) and to study the risk-benefit ratio on an individual basis. Moreover, patients should receive detailed information on the evaluation. Postmenopausal hormone replacement therapy does not induce significant hemostatic changes (especially with transdermal application) and is not associated with a proven risk of venous thromboembolism. Venous risk factors thus do not contraindicate the use of hormone replacement therapy, except perhaps in the immediate (one-year?) period after an acute event.