 Patients with hereditary antithrombin AT deficiency are at increased risk of venous thrombosis and pulmonary embolism, particularly during certain high risk procedures. The trial is focusing on patients with confirmed hereditary antithrombin deficiency who are undergoing a surgical procedure or inducedspontaneous labor and delivery. The study will test the safety and efficacy of recombinant human antithrombin rhAT by infusing rhAT prior to, during and following the period of risk or surgical procedure. 