1 Department of Obstetrics and Gynaecology, L747 Laboratory Block, LKS Faculty of Medicine, 21 Sassoon Road, Pokfulam, Hong Kong, SAR, People's Republic of China. dwchan@hku.hk.
2 Lee's Pharmaceutical (HK) Ltd, 1/F Building 20E, Phase 3, Hong Kong Science Park, Shatin, Hong Kong, People's Republic of China.
3 Department of Obstetrics and Gynaecology, L747 Laboratory Block, LKS Faculty of Medicine, 21 Sassoon Road, Pokfulam, Hong Kong, SAR, People's Republic of China.
4 Department of Obstetrics and Gynaecology, L747 Laboratory Block, LKS Faculty of Medicine, 21 Sassoon Road, Pokfulam, Hong Kong, SAR, People's Republic of China. hysngan@hku.hk.
5 Department of Obstetrics and Gynaecology, 6/F Professorial Block, Queen Mary Hospital, Pokfulam, Hong Kong, People's Republic of China. hysngan@hku.hk.