Who will not be able to get through NT?

NT is also called fetal neck hyaline zone examination, which is to check the thickness of fetal neck lymph fluid through B-ultrasound examination. The normal value should be less than 2.5. NT is also a kind of Down's screening in early pregnancy. Generally, the mother has been exposed to radioactive substances or the fetus of elderly mothers has a greater chance of chromosomal diseases, which may not pass the test.