1. Institute of Child and Adolescent Health, School of Public Health Peking University, National Health Commission Key Laboratory of Reproductive Health Beijing China
2. School of Population Medicine and Public Health Chinese Academy of Medical Sciences/Peking Union Medical College Beijing China
3. School of Public Health and Management Ningxia Medical University Yinchuan China
4. School of Nursing Peking University Beijing China
5. Department of Obstetrics and Gynecology Peking University First Hospital Beijing China