Does use of hormonal contraceptives among women with thrombogenic mutations increase their risk of venous thromboembolism? A systematic review.

Because use of combined oral contraceptives (COCs) confers some risk of venous thromboembolism (VTE), there is concern that this effect may be greater among women with thrombogenic mutations. We searched the MEDLINE and EMBASE databases for all articles published from January 1966 through September 2004 for evidence relevant to hormonal contraception and thrombogenic mutations. Of 301 articles identified by the search strategy, 16 evaluated COCs, and no studies were found for other hormonal methods. We used standard abstract forms and grading systems to summarize and assess the quality of the evidence. A total of 10 studies together provided "good" evidence of a greater risk of VTE (risk ratios of 1.3-25.1) and cerebral vein or cerebral sinus thrombosis among COC users with factor V Leiden mutation when compared with nonusers who have the mutation. The evidence for prothrombin and other thrombogenic mutations was not as strong as for factor V Leiden mutation. It is unclear whether the type of COC or duration of use modifies the risk of VTE among women with thrombogenic mutations.