1. Qingdao United Family Hospital, Qingdao, China
2. Assisted Reproductive Technology Unit, Department of Obstetrics & Gynaecology, The Chinese University of Hong Kong, Hong Kong
3. Obstetrics and Gynaecology, Queen Mary Hospital, Hong Kong, China
4. Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Hong Kong, Hysteroscopy centre, Fuxing Hospital, Beijing, China