Choosing an anticoagulant during pregnancy: usually heparin

(1) The precise risk of deep vein thrombosis during pregnancy is poorly documented, particularly among women with a history of thromboembolism. (2) Anticoagulant therapy is poorly assessed in pregnant women. (3) Unfractionated heparin remains the reference for use during pregnancy, based on extensive experience and lack of teratogenicity. (4) Low molecular weight heparins have no demonstrated advantage over unfractionated heparin in terms of their risk-benefit ratio, but they do have certain practical advantages. (5) Vitamin K antagonists such as warfarin carry a risk of fetal toxicity if taken between the 6th and 12th weeks of pregnancy (nasal and epiphyseal abnormalities). The latency and duration of effects makes them more difficult to use than heparin, especially towards the end of pregnancy. However, they seem to be more effective than heparin in patients with mechanical cardiac valve prostheses.