1. Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong, China
2. Obstetrics and Gynaecology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
3. Department of Obstetrics and Gynaecology, Hong Kong, The Chinese University of Hong Kong, Hong Kong, China
4. Department of Obstetrics and Gynaecology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
5. Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong, China
6. King' College London, London, United Kingdom of Great Britain and Northern Ireland