Venous thromboembolism (VTE) is an important cause of post-operative morbidity and mortality in women undergoing surgery for gynecologic malignancies. Although the benefit of thromboprophylaxis in reduction of post-operative VTE events after surgery for gynecologic cancers has been well documented around the world, the evidence for Chinese women is rare. The investigators designed this prospective and randomized study to assess the benefit of pharmacologic prophylaxis for patients received surgical treatment for gynecologic malignancies in China.