The normal 4D baby nasal bone is 7mm. Fetal nasal bone begins to develop in the 6th week of the embryonic period, and ossifies through membranous osteogenesis at 9-11 weeks of pregnancy, and is also an ultrasound examination for screening the risk of chromosomal disorders in the fetus during pregnancy, the normal value of fetal nasal bone in 4D ultrasound examination is 7mm, and when ultrasound examination suggests that the nasal bone is absent or the segment of the nasal bone is short, it can suggest that there is an increased risk of chromosomal disorders in the fetus. When ultrasonography suggests abnormal nasal bone, prenatal counseling and prenatal diagnosis, such as amniocentesis, are required to rule out the risk of chromosomal disorders in the fetus. When prenatal diagnosis suggests that the fetus has a combined chromosomal disorder, timely termination of pregnancy is required as prescribed by the doctor. However, when chromosomal disorders are ruled out, strict follow-up prenatal checkups are required. Pregnant women should pay attention to the prenatal examination during pregnancy, actively listen to the professional doctor’s advice to do a comprehensive nursing care, pay attention to rest, at the same time, should relax, avoid tension, anxiety, any discomfort should be timely to the hospital, the doctor to clarify the diagnosis, and cooperate with the doctor to deal with the symptoms.