Inherited thrombophilia and pregnancy: The obstetric perspective

The identified main causes of inherited thrombophilia are deficiencies of a ntithrombin (AT), protein C, or protein S, resistance to activated protein C associated with Factor V Leiden mutation, mutant factor II, and inherited hyperhomocysteinemia. For women from symptomatic families, these defects m ay be associated with an increased risk of venous thrombosis during pregnan cy and/or recurrent fetal loss. Inherited thrombophilia is common and appea rs to be a multigenic disorder. The thrombotic risk seems to be greatest fo r women who have AT deficiency or more than one thrombophilic defect. The a bnormalities that are now recognized are only part of the genetic predispos ition to thrombosis. When assessing thrombotic risk during pregnancy, acqui red risk factors as well as genetic predisposition should be considered. In creasing age, obesity, immobility, and delivery by cesarean section are maj or acquired risk factors. pregnancy should be planned as far as possible, a nd each patient should be managed individually. During pregnancy, heparin i s the anticoagulant of choice, and treatment with warfarin should be avoide d because of risks for the fetus. When patients receive long-term treatment with warfarin, pregnancy should be avoided or planned, and warfarin should be discontinued before conception or as soon as pregnancy is confirmed and before 6-weeks' gestation. For women who have AT deficiency, the incidence of thrombosis during pregnancy is between 20 and 40%. Adjusted-dose hepari n throughout pregnancy is recommended, followed by warfarin for at least 3 months postpartum For patients who have Factor V Leiden, mutant factor II, or a deficiency of protein C or protein S, treatment can be based on person al and family history. Thromboprophylaxis during late pregnancy and postpar tum should be considered. Fetal loss may be increased for women with inheri ted thrombophilia. The risk appears to be greatest for women with AT defici ency and women with more than one thrombophilic defect. For women with recu rrent fetal death and inherited thrombophilia, a number of case reports cla im that prophylaxis with heparin during pregnancy has resulted in successfu l pregnancy.