Pregnancy is accompanied by altered levels of coagulation factors, which are likely responsible for an increased risk of thrombosis, including an increased risk of deep vein thrombosis, pulmonary embolism, stroke and myocardial infarction. Women with thrombophilia, an acquired or inherited predisposition to thrombosis, are at an even greater risk of thrombosis during pregnancy than other women. The presence of thrombophilia, which may protect women from blood loss at the time of childbirth, does not improve the outcome of pregnancy. Women with thrombophilia are more likely to experience placental abruption, preeclampsia, fetal growth restriction, stillbirth, and possibly recurrent miscarriage. There are no randomized trials of the use of anticoagulation to reduce maternal thromboembolism, but in women with thrombophilia and a history of thrombosis, anticoagulation is generally recommended. In women with thrombophilia and a history of poor pregnancy outcome, anticoagulation may improve fetal outcomes.