1. Chalmers Sexual and Reproductive Health Centre; Edinburgh UK
2. Department of Obstetrics and Gynaecology; University of Hong Kong; Queen Mary Hospital; Hong Kong Hong Kong
3. Shenzhen Key Laboratory of Fertility Regulation; Reproductive Medicine Centre; The University of Hong Kong-Shenzhen Hospital; Shenzhen China
4. Department of Women's and Children's Health; Division of Obstetrics and Gynaecology; Karolinska Institutet; Karolinska University Hospital; Stockholm Sweden