Both color ultrasound and negative ultrasound are available for NT, most of them are performed color ultrasound, and negative ultrasound can be chosen if there are some special circumstances. NT examination is also called posterior nuchal translucency scan, mainly through the ultrasound to measure the thickest part of the fetal nuchal translucency layer of subcutaneous echogenicity, most of the pregnant women in the 11-13 ⁺ ⁶ weeks between the NT examination through the abdominal ultrasound can be clearly scanned to the posterior nuchal translucency band, this time do not need to hold urine, and abdominal ultrasound is more convenient. Some pregnant women may not be able to see the abdominal ultrasound clearly due to excessive obesity, at this time, you can also choose the vaginal ultrasound, mainly from the vagina for observation, the results of this examination is also more accurate, but there may be some discomfort. NT examination is a more important test, mainly to assess the risk of fetal chromosomal abnormalities, it is recommended to choose color ultrasound or yin ultrasound under the guidance of the doctor for examination.