Abstract

PIP: Pregnancy and oral contraceptives (OCs) reduce the levels of the natural anticoagulant protein S and about 50% and 20%. respectively. Original work on the link between OCs and development of deep vein thrombosis and pulmonary embolism do not necessarily confirm an association, today since it included cohort studies of women using high estrogen OCs. Also, physicians tended to actively diagnose thrombophlebitis in women they knew were using OCs. Objective diagnostic measures, e.g., venography, were not used in the cohort studies. Decreased estrogen content of current OCs and a case control study design show the likelihood of thrombotic complications of OS use has decreased significantly. Women who have experienced an episode of venous thrombosis and are not on oral anticoagulation therapy should not use OCs, because as many of 30% experience a second episode. Women with a strong family history of thromboembolism and those with antiphospholipid antibodies who have experienced a thrombotic event should also not use OCs. Current or past use of low estrogen Ocs does not significantly increase the risk of myocardial infarction, but smoking does. Physicians doe not know, however, whether women who use an OC with at the most 30 mcg estrogen and who smoke are at greater risk than those who smoke but do not use OCs. Just one study suggests a possible association between OC use and mitral valve prolapse leading to a cerebrovascular accident. The likelihood of developing calf vein clots in women who use low-dose OCs appears to be reduced, if they use sequential compression stockings and subcutaneous low molecular weight heparin following surgery. Since OCs decrease the chance of serious bleeding during ovulation and of heavy menstrual flow, oral anticoagulation is not a contraindication to OC use. The risk of OC-associated thromboembolism is considerably lower than that of pregnancy-associated thromboembolism.