1. Department of Anesthesiology, The Second Affiliated Hospital of University of South China, Hengyang, Hunan 421001, P.R. China
2. Hunan Province Key Laboratory of Tumor Cellular & Molecular Pathology, Cancer Research Institute, University of South China, Hengyang, Hunan 421001, P.R. China
3. Department of Gynecology, Foshan First People's Hospital, Foshan, Guangdong 528000, P.R. China
4. Department of Histology and Embryology, Clinical Anatomy and Reproductive Medicine Application Institute, University of South China, Hengyang, Hunan 421001, P.R. China
5. Department of Gynecology, The First Affiliated Hospital of University of South China, Hengyang, Hunan 421001, P.R. China
6. Department of Obstetrics, The First Affiliated Hospital of University of South China, Hengyang, Hunan 421001, P.R. China