1. Center for Reproductive Medicine , Department of Obstetrics and Gynecology, , Beijing , China
2. Peking University Third Hospital , Department of Obstetrics and Gynecology, , Beijing , China
3. National Clinical Research Center for Obstetrics and Gynecology (Peking University Third Hospital) , Beijing , China
4. Key Laboratory of Assisted Reproduction (Peking University), Ministry of Education , Beijing , China
5. Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproductive Technology , Beijing , China