Low Molecular Weight Heparin for Pregnant Women With Thrombophilia: a Prospective, Randomized, Open Trial

Women with thrombophilia, i.e. carriage of a factor V leiden mutation, a factor II prothrombin G20210A mutation or a reduced amount of antithrombin III, protein C or protein S, are at elevated risk for thrombosis and related sequelae. Specifically, pregnant women with thrombophilia are at risk for pregnancy-associated thrombosis, pregnancy-associated thromboembolism as well as early miscarriage (until 20 weeks gestation) late miscarriage (after 20 weeks gestation), preeclampsia, and intrauterine growth retardation <10th percentile. Uncontrolled retrospective and prospective studies indicate that a therapy with unfractionated heparin or low molecular weight heparin in pregnancy significantly reduces these pregnancy complications and improves maternal and fetal outcome. The use of low molecular weight heparin in pregnancy is safe with complication rates between 1% and 3%, mainly thrombocytopenia and bleeding complications. Randomized trials to adequately assess the safety and efficacy of heparin in pregnant women with thrombophilia are not available to date. Thus, we intend to randomize pregnant women with thrombophilia during weeks of gestation 11 to 14 into a therapy with nadroparin calcium (fraxiparin®) 0.3 mL daily during pregnancy and six weeks post partum and usual care. The primary end point of this study is a composite endpoint of pregnancy-associated thrombosis, pregnancy-associated thromboembolism, early miscarriage (until 20 weeks gestation) late miscarriage (after 20 weeks gestation), preeclampsia, and intrauterine growth retardation <10th percentile. We hypothesize that a prophylactic therapy with nadroparin calcium will significantly reduce pregnancy complications in pregnant women with thrombophilia.