1. Reproductive Medicine Center, Xiangya Hospital of Central South University, Changsha, Hunan, P.R. China
2. Clinical Research Center for Women’s Reproductive Health in Hunan Province, Changsha, Hunan, P.R. China
3. Department of Gynecology and Obstetrics, Baoding No.1 Central Hospital, Baoding, Hebei, P.R. China