We observed a patient who had a unilateral leg edema soon after lumbar spine surgery in the prone position. Spine patients have a number of risk factors for developing deep vein thrombosis (DVT) after or during surgery. These factors are; lengthy operative procedures, prone positioning on certain frames, and prolonged bed rest after surgery. Like these patients, estrogen users for replacement or contraception are three to four times more likely to develop DVT than non-users. So, anesthesiologist should check the risk factors of DVT in hormone replacement therapy users before major spine surgery, and perform antithrombotic prophylaxis, including elastic stocking, pneumatic compression to the calf and thigh, and careful prone positioning to avoid compression of the inguinal area. A special survey should be performed to evaluate whether postmenopausal women should discontinue hormone use before major spine surgery.