Risk factors for pulmonary embolism is similar to deep vein thrombosis. This includes poor blood flow and hypercoagulable states (a condition in which there is an abnormal increased tendency toward blood clotting). Conditions that put patients at high risk for DVT include spinal cord injury, major trauma, major general surgery. The use of chemotherapy, oral contraceptive therapy, hormone replacement therapy and paralytic stroke may also increase the risk of DVT. Other conditions that confer risks include obesity, bed rest for more than three days, and immobility due to sitting and varicose veins.