The screening test is only a primary screening and cannot diagnose 100% of the fetus with abnormalities, so an in-depth non-invasive prenatal genetic test or amniocentesis must be performed to confirm whether the fetus has the disease. Amniocentesis is a procedure in which the amniotic fluid of a pregnant woman is extracted for karyotyping of the fetus, which is the gold standard for diagnosing chromosomal disorders in the fetus. If the amniocentesis test confirms that the fetus has a chromosomal abnormality, such as trisomy 21, it is usually necessary to induce labor as soon as possible and abandon the fetus; if the puncture results show no problems, the risk of the fetus having a chromosomal disorder can basically be excluded and the fetus can be kept. Children diagnosed with Down’s syndrome have the following clinical symptoms after birth: 1. special facial features: children with special facial features with dull expressions, such as small eye slits and wide eye spacing; 2. intellectual backwardness: the most serious and prominent clinical manifestation of Down’s syndrome; 3. growth retardation: lower length and weight at birth than normal newborns, and delayed physical and motor development; 4. malformations: boys with cryptorchidism, poor fertility, girls without menstruation, the possibility of congenital heart disease or digestive tract malformations; 5, skin lines characteristics: the palm of the hand appears ape lines, commonly known as through the palm, that is, only a line across the palm of the hand.