1. Department of Obstetrics and Gynaecology, Fetal Medicine Unit, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong;
2. Department of Obstetrics and Gynaecology, Hospital Tengku Ampuan Afzan, Kuantan, Pahang, Malaysia;
3. Department of Prenatal Diagnosis and Therapy, Hospital Raja Permaisuri Bainun, Perak, Malaysia;
4. Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong