Perinatal aspects of inherited thrombophilia

The identified main causes of inherited thrombophilia are deficiencies of antithrombin, protein C and protein S, activated protein C (APC) resistance and the factor V Leiden mutation, mutant factor II, and inherited hyperhomocysteinemia. In women from symptomatic families these defects may be associated with an increased risk of venous thrombosis in pregnancy and recurrent fetal loss. Inherited thrombophilia is common and appears to be a multigene disorder. The thrombotic risk would seem to be greatest in women with antithrombin deficiency and more than one thrombophilia defect. The abnormalities that are now recognized represent only part of the genetic predisposition to thrombosis. In assessing thrombotic risk in pregnancy, acquired risk factors as well as genetic predisposition should be considered. Increasing age, obesity, immobility, and delivery by cesarean section are major risk factors. Pregnancy should be planned, and each patient should be managed on an individual basis. In pregnancy, heparin is the anticoagulant of choice, and as far as possible, treatment with warfarin should be avoided because of the risks to the fetus. When patients are on long-term treatment with warfarin, pregnancy should be avoided, and warfarin should be discontinued prior to embarking on a pregnancy or as soon as pregnancy is suspected and before 6 weeks' gestation. In women from symptomatic families with antithrombin deficiency, adjusted dose heparin throughout pregnancy is recommended and warfarin for at least 3 months post partum. In protein C and protein S deficiency, factor V Leiden, or mutant factor II, treatment can be based on personal and family history. Thromboprophylaxis in late pregnancy and post partum should be considered. Fetal loss may be increased in women with inherited thrombophilia. The risk appears greatest in women with antithrombin deficiency and women with more than one thrombophilia defect. A number of reports have claimed that prophylactic treatment with heparin during pregnancy has resulted in successful pregnancy in women with recurrent fetal death and inherited thrombophilia.