Currently, there are 3 methods of screening for Down syndrome in Vietnam: Non-Invasive Prenatal Testing (NIPT) based on chromosomal information from fetus's DNA in the mother's peripheral blood, the double biochemical test based on PAPP-A (Pregnancy Associated Plasma Protein A) and Free β-hCG in trimester 1, and the triple biochemical test which is based on AFP (Alpha Fetoprotein), hCG (Human Chorionic Gonadotropin) and uE3 (unconjugated Estriol) in trimester 2. This evidence concerns the gene AFP and Down syndrome.