1. Department of Obstetrics and Gynaecology, Beijing Tongren Hospital, Capital Medical University, Beijing, China
2. Department of Obstetrics and Gynaecology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
3. Hysteroscopic Centre, Fuxing Hospital, Capital Medical University, Beijing, China
4. Department of Obstetrics and Gynaecology, Monash University, Clayton, Australia
5. Aberdeen Centre for Women’s Health Research, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, United Kingdom