The special appearance of Down’s syndrome patients includes wide eye spacing, upward slanting of the outer corners of the eyes, inner canthus, low ear position, low nasal bridge, wide and thick tongue, often half-open mouth or tongue sticking out of the mouth, deep and many tongue clefts, thick palms with short and thick fingers, short and small last fingers often bent inward or with two knuckles, and 40% of children with through palms. In the metatarsal pattern, the tibial arch in the ball area of the thumb, the distance between the thumb and the second toe is large, and the joint ligaments are lax or low muscle tone is seen. Tests required for patients with tibial arch of the ball of the bunion in the metatarsal pattern: Cord blood test: Usually can be performed after 17 weeks of gestation. 95% success rate in obtaining cord blood. The operation is more technically demanding and requires special training; general hospitals cannot perform this operation. The miscarriage rate is about 1 – 3.%. Cord blood test can detect not only the karyotype of Down’s syndrome, but also some hematologic abnormalities such as sickle cell anemia and hemophilia; intrauterine infectious diseases of the fetus such as rubella virus, cytomegalovirus and toxoplasmosis infection. Amniotic fluid chromosome test: Amniotic fluid chromosome test is an effective method for prenatal diagnosis of Down’s syndrome, and pregnant women with “high-risk” Down’s syndrome screening results need to confirm whether their fetus is a child with Down’s syndrome. The most common technique for prenatal diagnosis is amniocentesis, in which a needle is inserted into the amniotic fluid through the abdomen of the pregnant woman under the guidance of ultrasound, and the amniotic fluid is extracted for chromosomal analysis of fetal cells. It is suitable for pregnant women between 16-20 weeks of gestation. In addition to amniocentesis, other techniques to perform prenatal diagnosis include chorionic villus biopsy, fetal umbilical vein puncture, and fetoscopy. Prenatal screening serum markers: Down syndrome screening has been explored for many years using the measurement of maternal serum chorionic gonadotropin (HCG), alpha-fetoprotein (AFP), and free estriol (FE3), which is a mid-pregnancy indicator (after 13 weeks), and based on these three (HCG and AFP can also be measured) serological indicators, as well as maternal age and weight, it is estimated that The risk of having a child with Down’s syndrome is estimated based on these three indicators (HCG and AFP can also be measured), as well as the age and weight of the mother, and further confirmatory tests are performed depending on the risk rate. This method can detect about 60% of fetuses with Down syndrome. Fluorescence in situ hybridization: The corresponding part of chromosome 21 is used as a probe to hybridize with lymphocytes in peripheral blood or amniotic fluid cells, which can show three fluorescent signals of chromosome 21 in cells of Down syndrome patients. X-rays, ultrasound, ECG and EEG can be routinely done. Some children with Down syndrome can be found to have congenital heart disease, backward bone age, abnormal EEG and other changes.