van Vlijmen EF, Veeger NJ, Middeldorp S et al. Blood 2011;118:2055–61.
In the present study, the authors investigated the risk of venous thrombosis during combined oral contraceptive use and pregnancy in female patients with and without known thrombophilia. The major finding in the present study was the high pregnancy-related risk of venous thromboembolism, relative to the observed risk during combined oral contraceptive use; this should be taken into account when counseling contraceptive options.
Because of the increased thrombotic risk associated with combined oral contraceptive use in females with known thrombophilic mutations (i.e. antithrombin deficiency, protein C deficiency, protein S deficiency, factor V Leiden, and prothrombin-G20210A), the World Health Organization recommendations state that combined oral contraceptive use in these women should be strongly discouraged because of an unacceptable health risk. This severely limits these women in terms of their contraconceptive possibilities.