If the nasal bone is not seen in the NT test, most of the reasons are that the cut is not typed or it is too small to show well and needs to be seen again after some time, in a few cases it is considered possible that it is because the nasal bone is missing. At this time, depending on the maternal risk, the patient is advised to do further prenatal diagnosis, which requires chromosomal examination to rule out chromosomal abnormalities. It is also necessary to randomly observe the chromosomal abnormalities according to their manifestations. Some patients may see the development of nasal bone at a later stage or have a simple case of missing nasal bone.