Recent prospective and retrospective family studies support the view that deficiencies of the naturally occurring anticoagulants (antithrombin, protein C and protein S) are of greater clinical significance than heterozygous carriage of factor V Leiden or the prothrombin gene mutation.59,76
Recent studies have been consistent with a higher risk of pregnancy-related VTE in women who are antithrombin deficient or who are homozygous for factor V Leiden, the prothrombin gene mutation or are compound heterozygotes for factor V Leiden and the prothrombin gene mutation.61,62,77,78
Women should be stratified according to both the level of risk associated with their thrombophilia (see Table below) and the presence or absence of a family history or other risk factors.79
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76. Mahmoodi BK, Brouwer JL, ten Kate MK, Lijfering WM, Veeger NJ, Mulder AB, et al. A prospective cohort study on the absolute risks of venous thromboembolism and predictive value of screening asymptomatic relatives of patients with hereditary deficiencies of protein S, protein C or antithrombin.
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85. van Boven HH, Vandenbroucke JP, Briët E, Rosendaal FR. Gene-gene and gene-environment interactions determine risk of thrombosis in families with inherited antithrombin deficiency. Blood 1999;94:2590–4.
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87. McColl MD, Ramsay JE, Tait RC, Walker ID, McCall F, Conkie JA, et al. Risk factors for pregnancy associated venous thromboembolism. Thromb Haemost 1997;78:1183–8.
88. Martinelli I, Battaglioli T, De Stefano V, Tormene D, Valdrè L, Grandone E, et al.; the GIT (Gruppo Italiano Trombofilia). The risk of first venous thromboembolism during pregnancy and puerperium in double heterozygotes for factor V Leiden and prothrombin G20210A. J Thromb Haemost 2008;6:494–8.
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