Ultrasound NT is to check the thickness of fetal nuchal translucency.NT is the abbreviation of fetal nuchal translucency thickness, which means the thickness of the subcutaneous tissue at the back of the neck of the fetus with the translucency band.The normal value of NT is less than 3mm, and the upper limit of NT value should not be more than 2.2mm at about 11 weeks of pregnancy.At 13-15 weeks of pregnancy, the upper limit of NT value should not be more than 2.8mm.If NT value is more than or equal to 3mm when checking around 13 weeks of pregnancy, chromosomal examination is recommended to rule out Down’s Syndrome. If the NT value is greater than or equal to 3mm, it is recommended to do a chromosomal test to rule out Down’s syndrome. Note that the measurement requires the ruler to be placed on the inner edge of the skin, and the time for the test is usually around 13 weeks of pregnancy, so do not miss this time. If the pregnant woman is not very fat, you can directly do ultrasound or color ultrasound for examination. If the pregnant woman is particularly fat and the abdominal wall is particularly thick, the color ultrasound observation is not clear and affects the measurement, you can take to do a negative ultrasound for examination.