[1] The University of Hong Kong,Department of Paediatrics and Adolescent Medicine, LKS Faculty of Medicine
[2] Department of Obstetrics and Gynaecology,Prenatal Diagnostic Laboratory
[3] Queen Mary Hospital,Department of Health
[4] Tsan Yuk Hospital,Department of Obstetrics and Gynaecology
[5] Clinical Genetic Service,Department of Obstetrics and Gynaecology
[6] Queen Elizabeth Hospital,undefined
[7] The University of Hong Kong,undefined