The NT test is an early pregnancy ultrasound, while the Down screening is a combined serologic marker screening during pregnancy, and they are different prenatal screening modalities. NT test is a method of checking the thickness of fetal nuchal translucency (NT) by ultrasound at 11-13+6 weeks of gestation, which is used to ultrasonographically screen the fetus for the risk of aneuploid chromosomal abnormalities, such as Down’s syndrome. Down’s screening is used to screen for the risk of Down’s syndrome, trisomy 18 and neural tube defects by screening for serologic markers such as alpha-fetoprotein (AFP), human chorionic gonadotropin (HCG), and free estriol (uE3). Down’s screening is divided into 11-13⁺⁶ weeks in early pregnancy and 16-19⁺⁶ weeks in mid-pregnancy, and mid-pregnancy screening is now largely discarded because of its low accuracy. However, both NT test and Down’s syndrome screening are prenatal screening methods, and a negative result does not completely exclude the possibility of abnormal development of the fetus. A positive result is not diagnostic either, it just means that the risk of the disease is elevated and further confirmatory tests, such as amniocentesis, need to be performed as prescribed by the doctor.