1. Department of Obstetrics and Gynecology, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
2. Reproductive and Stem Cell Research Institute, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China
3. Department of Pathology, Xiangya Hospital of Central South University, Changsha, Hunan 410008, P.R. China