Down’s syndrome is actually a chromosomal abnormality, also known as trisomy 21, because the normal human chromosomes are two in number, but there are three chromosomes in number 21, so it is trisomy 21. The main manifestation is congenital stupidity and mental retardation, which has a typical clinical symptom, namely the facial features, wide eye spacing, poorly developed nasal bridge and nasal bones, and a protruding tongue, so the child looks like a congenital stupid, obtuse face. Some children may have a combination of through palm, that is, both hands are through palm, or some folk say broken hand, so this is a congenital genetic disease. At present, our country is focused on prenatal screening for Down’s syndrome, requiring every pregnant woman to undergo Down’s syndrome screening or non-invasive prenatal DNA testing in early or mid pregnancy.