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.

Inclusion Criteria:

• Patients of ovarian cancer, cervix cancer or endometrial cancer;
• Age ≤ 70 years; female, Chinese women;
• Initial treatment is surgery;
• Laboratory tests: WBC ≥ 4×10(9)/L, NEU ≥ 2×10(9)/L, PLT ≥ 100×10(9)/L, serum bilirubin ≤ 1.5 times the upper limit of normal, transaminase ≤ 1.5 times the upper limit of normal, BUN, Cr ≤ normal
• No prior pharmacologic prophylaxis;
• Provide written informed consent.

Exclusion Criteria:

• PLT ≤ 75×10(9)/L
• Vascular injury
• History of thrombosis
• Liver and kidney dysfunction
• Concurrently participating in other clinical trials
• Unable or unwilling to sign informed consents;
• Unable or unwilling to abide by protocol.