1. School of Medicine Renji Hospital Shanghai Jiaotong University Shanghai China
2. Beijing Obstetrics and Gynecology Hospital Capital Medical University Beijing China
3. The Fourth Hospital of Shijiazhuang Shijiazhuang China
4. Affiliated Hospital of Jining Medical University Jining China
5. Changzhi Maternity and Child Health Care Hospital Changzhi China
6. The Third Affiliated Hospital of Zhengzhou University Zhengzhou China
7. Fujian Maternity and Child Health Care Hospital Fuzhou China
8. The First Affiliated Hospital of Zhengzhou University Zhengzhou China
9. Shengjing Hospital Affiliated of China Medical University Shenyang China
10. West China Second University Hospital Sichuan University Chengdu China
11. Fudan University Affiliated Hospital of Obstetrics and Gynecology Shanghai China
12. Anhui Women and Child Health Care Hospital Hefei China
13. Peking University Third Hospital Beijing China
14. School of Medicine Shanghai Jiaotong University Shanghai China