1. Department of Obstetrics and Gynecology Peking Union Medical College HospitalPeking Union Medical CollegeChinese Academy of Medical Sciences Beijing China
2. Department of Obstetrics and Gynecology Women’s HospitalSchool of MedicineZhejiang University Hangzhou Zhejiang Province China
3. Department of Obstetrics and Gynecology Hunan Maternal and Child Health Care Hospital Changsha Hunan Province China
4. Department of Obstetrics and Gynecology Northwest Women and Children’s Hospital Xi’an Shanxi Province China
5. Department of Obstetrics and Gynecology Shandong Provincial Hospital Affiliated with Shandong University Jinan Shandong Province China
6. Department of Obstetrics and Gynecology Beijing Obstetrics and Gynecology HospitalCapital Medical University Beijing China
7. Department of Obstetrics and Gynecology Ruijin Maternal and Child Health Hospital Ruijin Jiangxi Province China
8. Department of Obstetrics and Gynecology Sichuan UniversityWest China Second Hospital Chengdu Sichuan Province China
9. Department of Obstetrics and Gynecology The First Clinical Hospital Affiliated with Harbin Medical University Harbin Harbin Province China
10. Department of Obstetrics and Gynecology Nanfang HospitalSouthern Medical University Guangzhou Guangzhou Province China
11. Department of Obstetrics and Gynecology Beijing Haidian Maternal and Child Health Hospital Beijing China
12. Department of Obstetrics and Gynecology Henan Provincial People’s Hospital Zhengzhou Henan Province China
13. Department of Obstetrics and Gynecology Shengjing Hospital Affiliated with China Medical University Shenyang Liaoning Province China
14. Department of Obstetrics and Gynecology Harbin Nangang District Maternity Hospital Nangang Harbin Province China