T21 high risk means that when screening for Down syndrome is performed, it indicates that the fetus is at high risk of developing trisomy 21. The main methods of screening for trisomy 21 during pregnancy include biochemical testing for Down’s syndrome and non-invasive DNA testing. When Down’s syndrome screening suggests a high risk of trisomy 21, it means that the fetus has the possibility of Down’s syndrome and further testing is needed, including non-invasive DNA testing for genes and amniocentesis. Among them, amniocentesis is the gold standard, which can confirm whether the fetus has Down syndrome by directly extracting the fetus’ shed cells for karyotype analysis. After birth, children with Down’s syndrome generally present with a peculiar facial appearance, intellectual backwardness and developmental delay, and may be accompanied by a variety of malformations and low life skills. As Down’s syndrome is a chromosomal disorder, there is no good clinical treatment. It is recommended that pregnant mothers must have regular maternity checkups, and once the diagnosis of Down’s syndrome is confirmed, it is generally recommended to terminate the pregnancy as soon as possible.