NT (nuchal translucecy) is an abbreviation for fetal nuchal translucent membrane, a translucent protein membrane that surrounds the back of the fetal neck with mobility around 10 to 13 gestations. Its thickness is positively correlated with Down’s Sydrome (defect) and can be measured by ultrasonography. Fetal nuchal translucency is the thickness between the fetal dorsal soft tissue and the skin and is considered to be the most effective indicator for screening Down’s syndrome fetuses because Down’s syndrome children tend to have soft tissue edema in the neck, whereas normal fetuses do not have this abnormal sign. It has been suggested that the cause of thickened fetal nuchal translucent tissue may be related to cardiac failure in fetuses with early severe cardiac malformations such as ventricular septal defect and aortic stenosis due to chromosomal abnormalities, while the development of cephalic and cervical vessels and lymphatic vessels is incomplete; it has also been reported that if a fetus shows abnormal fetal nuchal translucent tissue thickness in early pregnancy, its development of Down’s syndrome or other trisomy It has been reported that the chance of Down syndrome or other trisomic syndromes is 13 times higher if the fetus shows abnormal nuchal translucency in early pregnancy, and it has diagnostic significance from 10 to 22 weeks of gestation, but the diagnostic value is highest from 10 to 14 weeks of gestation. Generally, NT values below 3.0 are considered normal.