1. Department of Gynecology and Obstetrics, Peking University People’s Hospital, Beijing, P. R. China;
2. Department of Gynecology and Obstetrics, The First People’s Hospital of Yunnan Province, Kumming City, P. R. China;
3. Department of Gynecology and Obstetrics, Tianjin Medical University Cancer Institute and Hospital, Tianjin, P. R. China