1. Departments of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR.
2. Obstetrics and Gynecology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR
3. Nuffield Department of Obstetrics and Gynecology, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom