Venous thromboembolism is an important cause of maternal morbidity and mortality throughout the developed world with an incidence of about 1 per 1000 deliveries, of which 1-2% are fatal. Two thirds of women who have a pregnancy-associated deep vein thrombosis develop the post-thrombotic syndrome and suffer long-term morbidity. The risk of venous thromboembolism is greater in older women and in women who have an operative delivery. Other risk factors include obesity, high parity, and immobilization. Acquired or inherited thrombophilias augment the risk, and some women with a previous history of venous thromboembolism may be at increased risk of a recurrence associated with pregnancy. Arterial thrombosis is uncommon in pregnancy but may have devastating consequences. The incidence of ischemic stroke associated with pregnancy is unknown but is estimated to be about 0.18 per 1000 deliveries-the majority being the result of arterial occlusion. Myocardial infarction is estimated to occur in 0.1 per 1000 women in association with pregnancy. Events occur most frequently peripartum or postpartum. Risk factors include maternal age, atherosclerosis, obesity, hypertension, and smoking.