1. Department of Obstetrics and Gynecology, Peking University Third Hospital, Beijing, China
2. National Clinical Research Centre for Obstetrics and Gynaecology, Beijing, China
3. National Centre for Healthcare Quality Management in Obstetrics, Beijing, China
4. School of Biological Science and Medical Engineering, Beihang University, Beijing, China
5. Department of Maternal and Child Health, Peking University School of Public Health, Beijing, China
6. Department of Medical Affairs, Peking University Third Hospital, Beijing, China
7. Department of Healthcare Quality Evaluation, Bureau of Medical Administration, National Health Commission of the People’s Republic of China, Beijing, China