1. Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin 300052, P.R. China
2. Department of Gynecology and Obstetrics, Peking University People's Hospital, Beijing 100044, P.R. China
3. Department of Gynecology and Obstetrics, Tianjin Metabolic Diseases Hospital and Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, P.R. China
4. Department of Gynecology and Obstetrics, Tianjin Jinghai Hospital, Tianjin 301600, P.R. China
5. Department of Clinical Laboratory, Tianjin Huanhu Hospital, Tianjin 300350, P.R. China