1. Department of Obstetrics and Gynecology Nanfang Hospital Southern Medical University Guangzhou China
2. Department of Obstetrics and Gynecology People’s Hospital of Linyi City Linyi China
3. Department of Obstetrics and Gynecology Shenzhen Hospital of Peking University Shenzhen China
4. Department of Epidemiology College of Public Health Guangzhou Medical University Guangzhou China
5. Department of Obstetrics and Gynecology Peking Union Medical College Hospital Peking Union Medical College Beijing China