NT test is called nuchal translucency thickness measurement, which generally measures the thickness of the subcutaneous fat at the back of the neck. The normal range is within 2.5mm, more than 2.5mm is abnormal and other further tests are needed. If the NT is too thick, there may be several common abnormalities: 1. chromosomal abnormalities, non-invasive DNA or amniocentesis is needed to further check whether the fetus has chromosomal abnormalities. 2. it may indicate hydatidiform fetus, which may be related to the abnormal development of the fetal cardiovascular system. 3. there may be lymphoid cystic tumor formed by abnormal development of the lymphatic vessels in the neck, etc. If the NT is more than 2.5mm, go to If the NT is more than 2.5mm, you should go for prenatal consultation for further examination.