The main inherited thrombophilias (antithrombin deficiency, protein C and S 
deficiency, FVL, the prothrombin gene variant, and MTHFR C677T homozygotes) have 
a combined prevalence in Western European populations of 15% to 20%. One or more 
of these inherited thrombophilias is usually found in approximately 50% of women 
who have a personal history of VTE. Obstetricians must therefore be aware of the 
interaction between thrombophilias and the procoagulant state of pregnancy and 
should have an understanding of additional risk factors that may act 
synergistically with thrombophilias to induce VTE. Such knowledge combined with 
the appropriate use of thromboprophylaxis and treatment in women who have 
objectively confirmed VTE continue to improve maternal and perinatal outcomes.