Women with thrombophilia: Assessing the risks for thrombosis with oral contraceptives or hormone replacement therapy

Women with inherited or acquired thrombophilia are at increased risk for ve nous thromboembolism (VTE) when they use oral contraceptives (OCs) of eithe r the second or third generation. For women who are heterozygous for Factor V Leiden, the risk is probably 28 to 50 of 10,000 women-gears compared to 2 to 5 of 10,000 years for those not known to have thrombophilia. The throm botic risk is highest during the first year that OCs are used. Whether wome n with thrombophilia are at increased risk for VTE when they use hormone re placement therapy (HRT) has not been assessed in any study. For women witho ut thrombophilia, the risk for VTE associated with HRT is probably 2 to 3 o f 10,000 years. The benefits of HRT include reduced risk for myocardial inf arction and Alzheimer's disease, and increased bone density. The physiologi cal changes induced by HRT are not the same as those induced by OCs. Small studies have suggested that for women who have additional risks of thrombos is (i.e., perioperative setting, underlying systemic lupus erythematosus), HRT does not confer the same increased risk of thrombosis, as does the use of OCs, Until data are available to address the magnitude of any increase i n thrombotic risk induced by HRT for women with thrombophilia, physicians p robably serve their patients best by providing information about the benefi ts of HRT, emphasizing that the risk of VTE is unknown, and encouraging pat ients to take an active role in decisions about their healthcare.