Higher Risk of Venous Thrombosis During Early Use of Oral Contraceptives in Women With Inherited Clotting Defects

Abstract
RESULTS OF recent studies1-4 show that the risk for venous thrombosis is highest during the initial period of oral contraceptive use. This confirms a clinical impression that has not been studied extensively.5-7 It was previously reported3,8 that factor V Leiden mutation, which leads to resistance to activated protein C and was found in about 1 of 5 patients with venous thrombosis, displays a strong interaction with use of oral contraceptives. Other inherited clotting defects that are themselves risk factors for venous thrombosis, such as protein C deficiency, protein S deficiency, antithrombin deficiency, and prothrombin 20210 A mutation, might also lead to a high risk of venous thrombosis when combined with oral contraceptive use.9