CHEUNG HH, TONG L-Y, TO WW. Second-tier non-invasive prenatal screening for Down syndrome in a public obstetric unit: the first 12 months. Hong Kong J Gynaecol Obstet Midwifery [Internet]. 2023 Apr. 6 [cited 2024 Nov. 24];22(1). Available from: https://hkjgom.org/home/article/view/307