1.What is NT test? What method is used? NT is the abbreviation of nuchal translucency in English, which is translated into Chinese as nuchal translucency, commonly known as a transparent band at the back of the fetus’ neck, so the method of examination is conceivably ultrasound. 2. When is the NT test done? What is it for? According to the guidelines of the American Congress of Obstetricians and Gynecologists, NT screening is best performed between 11 and 14 weeks of gestation, as it is too early to see NT and too late to detect abnormal fetal NT, which is a very precious window. So why exactly does NT respond to fetal genetic material abnormalities? If the genetic material is abnormal, it may lead to abnormal return, and a large amount of lymphatic fluid will accumulate under the neck, leading to thickening of NT under the ultrasound, which can indicate fetal genetic material abnormalities for early further treatment. After 14 weeks, even if the fetus with abnormal genetic material, NT will disappear, so if you miss this period, you cannot perform NT examination. 3.Do I need to hold urine before NT test? Generally speaking, it is not necessary to hold urine after 12 weeks for ultrasound, so there is no need to hold urine for NT examination in special cases. 4.What are the dangers of missing the timing of NT test? NT is the most sensitive indicator for early detection of fetal abnormalities, of course, the vast majority of pregnancies up to this period are normal, only about 4% of fetuses are abnormal, NT is the most sensitive indicator for early detection of fetal abnormalities, so try not to miss this test, of course, even if you miss it, there is no need to be overly nervous, after all, 96% of fetuses are normal. 5.Which is more accurate, NT test or Down’s syndrome screening? NT test is an imaging test, once NT is abnormal, there is a 1/6 chance that the fetus is chromosomally abnormal. Down’s syndrome screening is a serological test, once it indicates high risk, there will be 2.5% of fetus with chromosomal abnormality in all the indicated high risk. 6.NT test indicates low risk, is it still necessary to do Down screening? NT test does not indicate high risk and low risk like Down screening, if NT is greater than 3mm, it means that 1/6 of the fetus may have chromosomal abnormality, currently it is recommended to do CVS, that is, chorionic villus sampling, if chromosomal abnormality is identified, it can be treated as early as possible, but CVS has certain risk and high technical difficulty, so many pregnant mothers will still do amniocentesis to check fetal chromosome at a later stage instead of performing Down screening. The NT will not be performed again. If the NT is less than 3mm, it means that the risk of fetal chromosomal abnormalities is low. This test is more accurate.