 Patients with hereditary antithrombin deficiency are at increased risk of venous thrombosis and pulmonary embolism, particularly during certain high risk procedures. The trial focused on patients with confirmed hereditary antithrombin deficiency who were undergoing a surgical procedure or inducedspontaneous labor and delivery, andor caesarean section. The study assessed the incidence of thromboembolic events following prophylactic intravenous administration of recombinant human antithrombin rhAT to patients with hereditary antithrombin AT deficiency in situations usually associated with a high risk for thromboembolic events. 