Down’s syndrome is a basic means of screening for Down’s syndrome, a common chromosomal disorder in humans, and almost all pregnant women are now screened for Down’s syndrome because of the severe inferiority of children with Down’s syndrome and their complete inability to care for themselves. Data show that 80% of Down syndrome occurs among pregnant women over the age of 35, so every pregnant woman has the possibility of carrying a Down syndrome fetus. The Down’s serum test is a very effective way to screen for children with Down’s syndrome. The test is performed by taking blood from a pregnant woman and checking the concentration of alpha-fetoprotein, chorionic gonadotropin and free estriol in the mother’s serum and calculating the risk factor for congenital defects by taking into account the expected date of delivery, weight, age and the week of pregnancy when the blood is taken. The best time for this test is between the 11th and 13th week of pregnancy, which is also called early pregnancy screening. Of course, if you miss this time, then you can undergo midtrimester Down’s syndrome screening, which is usually done between 16 and 20 weeks of pregnancy. The results are usually available to the pregnant woman half a month after the blood draw. If the result is high risk, there is no need to panic, then further non-invasive dna, or chorionic villus biopsy (early pregnancy), amniocentesis, fetal chromosome test (mid pregnancy) can be done, so that the diagnosis can be clear.