1. Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
2. Department of Obstetrics and Gynecology, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
3. Department of Reproductive Medicine, The Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
4. Department of Gynecology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China
5. Department of Obstetrics and Gynecology, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
6. Department of Obstetrics and Gynecology, Women and Children’s Hospital of Jinzhou, Jinzhou, Liaoning, China
7. Department of Obstetrics and Gynecology, Xinhui Maternity and Children’s Hospital, Nanning, Guangxi, China
8. Department of Gynecology, Guangzhou Women and Children’s Medical Center, Guangzhou, Guangdong, China
9. Department of Obstetrics and Gynecology, Beijing Shijitan Hospital, Capital Medical University, Peking University Ninth School of Clinical Medicine, Beijing, China
10. Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Beijing, China