NT examination of the nasal bone is necessary, NT examination, or posterior nuchal translucency band scan, is a way to assess whether a pregnant woman’s baby may have Down syndrome in early pregnancy, through ultrasound to the baby’s back of the neck under the skin to measure the method of fluid accumulation, all babies should have some fluid in the back of the neck, and if the patient has Down syndrome, the posterior nuchal translucency band is thicker. Clinically it is necessary to pass a nasal bone NT test, children with Down syndrome have facial dysplasia, which often results in the absence of the nasal bone, an NT test can be performed to specifically bring out the nasal bone and determine if the child has Down syndrome, if the patient is found to have an absent nasal bone further screening is required to rule out the possibility of Down syndrome.