Fetal chromosomal abnormalities refer to abnormalities in the number and structure of chromosomes, the carriers of genetic material in fetal cells. It often manifests as multi-organ and multi-system malformations in the fetus, but there are many chromosomal abnormalities that do not show any morphological or structural abnormalities during fetal life. The diagnosis of chromosomal number and structure abnormalities is made by chorionic villus sampling, amniocentesis, umbilical vascular puncture, and fetal biopsy to obtain fetal cell cultures for karyotype analysis. Fetal chromosome structure and number cannot be directly observed by ultrasound. However, the development of genetic sonography in the past 10 years has accumulated a lot of rich clinical experience and testing data through meticulous and systematic research on the fetus. This has made it possible to screen for chromosomal abnormalities by prenatal ultrasound, which is receiving more and more clinical attention and is playing an unprecedented role in the eugenics of human beings. The higher the number of fetal abnormalities detected by prenatal ultrasound, the higher the likelihood of chromosomal abnormalities. In other words, the risk of chromosomal abnormalities increases with the number of abnormalities detected by ultrasound. The risk of chromosomal abnormalities increases with the number of abnormalities detected by prenatal ultrasound, and the likelihood of chromosomal abnormalities increases if other abnormalities are found in combination. Different types of structural malformations of the fetus can be present in a particular chromosomal abnormality. Each specific type of chromosomal abnormality has its own specific spectrum of abnormalities. For example, cleft lip and palate alone, clubfoot alone, cleft abdomen, jejunal atresia, large bowel obstruction, unilateral multiple cystic renal dysplasia, mesenteric cyst, hemivertebral malformation, cystic adenoma of the lung, and cleft brain malformation. For some specific malformations, the high risk of chromosomal malformations may be the opposite of the severity of a particular malformation. That is, the less severe the malformation, the greater the risk of chromosomal malformation in the fetus, while the more severe the malformation, the less the risk of chromosomal malformation in the fetus. For example, umbilical bulge, dilated ventricles, dilated renal pelvis, excessive amniotic fluid, intrauterine fetal growth retardation, etc. In general, when ultrasonography suggests an abnormality, especially when there is a high suspicion of other structural malformations associated with chromosomal malformations. The examiner should carefully examine all fetal structures and promptly look for possible structural abnormalities in the fetus. However, ultrasonography also has its limitations and is highly influenced by the fetal position. Therefore, once an abnormality is detected, it requires multidisciplinary participation and the information obtained is corroborated by each other to make a scientific and reasonable diagnosis. The purpose of eugenics can also be achieved.