1. Department of Obstetrics and Gynecology Hebei Yanda Hospital, affiliated to Hebei Medical University Beijing China
2. Department of Obstetrics and Gynecology China Meitan General Hospital (Emergency General Hospital) Beijing China
3. Department of Radiation Oncology Peking University School of Oncology, Peking University Cancer Hospital Beijing China
4. Wangjing Hospital China Academy of Chinese Medical Sciences Beijing China
5. Department of Obstetrics and Gynecology Sanya City Womenfolk and Infant Health Care Hospital Sanya City China
6. Department of Obstetrics and Gynecology Beijing Fengtai Hospital, affiliated Capital Medical University Beijing China