1. Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
2. Department of Obstetrics and Gynecology, Women and Children’s Hospital of Jinzhou, Jinzhou, 121000 Liaoning, China
3. Department of Obstetrics and Gynecology, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, 410008 Hunan, China
4. Department of Reproductive Medicine, The Second Hospital of Hebei Medical University, Shijiazhuang, 050000 Hebei, China
5. Department of Gynecology, The Affiliated Hospital of Qingdao University, Qingdao, 266500 Shandong, China
6. Department of Obstetrics and Gynecology, The Second Affiliated Hospital of Nanchang University, Nanchang, 330006 Jiangxi, China
7. Department of Obstetrics and Gynecology, Xinhui Maternity and Children’s Hospital, Nanning, 529100 Guangxi, China
8. Department of Gynecology, Guangzhou Women and Children’s Medical Center, Guangzhou, 510000 Guangdong, China
9. Department of Obstetrics and Gynecology, Beijing Shijitan Hospital, Capital Medical University, Peking University Ninth School of Clinical Medicine, Beijing 100038, China
10. Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Beijing 100010, China