1. Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China
2. National Engineering Research Center of Reproductive Health, National Research Institute for Family Planning, Beijing 100081, China
3. Reproductive Medical Center, Department of Obstetrics and Gynecology, Peking University International Hospital, Beijing 102206, China
4. Reproductive Medical Center, Department of Obstetrics and Gynecology, Peking University People’s Hospital, Beijing 100044, China