1. Department of Obstetrics and Gynaecology; Yong Loo Lin School of Medicine; National University of Singapore; Singapore
2. Department of Gynaecology & Obstetrics; Nanfang Hospital; Southern Medical University; Guangzhou China
3. Department of Laboratory Medicine; Molecular Diagnosis Centre; National University Hospital; Singapore
4. Centre for Research into Circulating Fetal Nucleic Acids; Li Ka Shing Institute of Health Sciences; Chinese University of Hong Kong; Shatin New Territories Hong Kong