NT refers to the fetal nuchal translucency and is mainly used to check the risk of chromosomal abnormalities in the fetus, but for is sometimes associated with cardiac malformations. The fetal nuchal translucency is viewed by ultrasound to check the thickness of the fetal nuchal translucency and the development of the nasal bone. Normal values are below 3.0mm. Excessive thickness of the nuchal translucency may be associated with fetal chromosomal karyotype abnormalities as well as other structural malformations, and it is recommended that further investigations, such as chorionic villus or amniocentesis, should be performed promptly. Fetal nuchal translucency can only be used as a prenatal screening test, and its abnormal thickening is related to chromosomal abnormality and fetal cardiac anomalies, but it cannot be used as the basis for diagnosis. Amniocentesis is needed to check the chromosomes and make the final diagnosis. If the presence of an abnormality is confirmed, consideration should be given to whether or not to terminate the pregnancy.