The most important risk factor for thrombosis in pregnancy is a history of thrombosis. Although both heparin and warfarin are satisfactory for use postpartum, including in women who are breastfeeding, many women prefer to use low-molecular-weight heparin (LMWH) (with once-daily dosing postpartum) because they have become accustomed to its administration and because they can avoid the monitoring associated with coumarin therapy. With massive life-threatening pulmonary thromboembolism (PE), the pregnant woman needs emergency assessment by a multidisciplinary team of obstetricians, surgeons, and radiologists, who should decide rapidly on appropriate treatment ranging from intravenous unfractionated heparin (UFH) to systemic thrombolysis, catheter thrombolysis or embolectomy, or surgical embolectomy. Women are at an increased risk of venous thromboembolism (VTE), during pregnancy. In anticipation of delivery, surgery, or other invasive procedures, anticoagulation should be manipulated to reduce the risk of bleeding complications while minimizing the risk of thrombosis.