1 a Department of Obstetrics and Gynaecology , University of Hong Kong, Queen Mary Hospital , Hong Kong.
2 b Shenzhen Key Laboratory of Fertility Regulation, Reproductive Medicine Center , The University of Hong Kong - Shenzhen Hospital , Shenzhen , PR China.
3 c Department of Women's and Children's Health, Division of Obstetrics and Gynaecology, Karolinska Institutet , Karolinska University Hospital , Stockholm , Sweden.