Down syndrome, also known as Down’s syndrome, is commonly referred to as trisomy 21. Mainly due to chromosomal abnormalities, that is, an extra chromosome 21 caused by the disease, 60% of the children in the uterus will be early miscarriage, the survival of the performance of the obvious backwardness of the intellectual development of the manifestations of special facial features, developmental disorders, and even multiple malformations. These children have distinctive facial features, such as wide eye spacing, low nasal bridge, upward slanting of the outer canthus of the eyes, a fat tongue that often protrudes out of the mouth and is accompanied by salivation, a relatively short stature, difficulty in feeding, a lower intellectual ability than normal children, delayed motor and sexual development, often accompanied by congenital anomalies, and a relatively low level of immune function, making them susceptible to a wide range of infections. Diagnosis is mainly through the karyotype analysis, can be found in the body more than 1 21 chromosome, there is no very effective treatment, the best means is in the pregnant woman prenatal diagnosis, prenatal termination of pregnancy. Therefore, pregnant women should do a good job of prenatal prevention in pregnancy, mainly good genetic counseling, the older the pregnant woman, the higher the risk rate, do prenatal diagnosis, to prevent the birth of children with Down syndrome the most effective measures.