The normal range of risk values for Trisomy 21 is less than 1/270. Trisomy 21, also known as Down’s syndrome, is an autosomal malformation genetic disorder, the cause of which is related to the mother’s gestational age, genetic factors, the use of chemical abortions during pregnancy, radiation exposure, autoimmune diseases and viral infections. Screening for trisomy 21 is usually done at around 15-20 weeks of pregnancy. During the test, chorionic gonadotropin, free estriol, alpha-fetoprotein and other indicators in the pregnant woman’s blood are measured at the same time, and then combined with the mother’s age, gestational week, weight, etc., to make a comprehensive assessment of the risk of the fetus for Down’s syndrome. If the test value is significantly higher than 1/270, it means that the child has a significantly higher risk of developing trisomy 21. Further testing is required. If the test value is significantly less than 1/270, the risk of the child developing trisomy 21 is relatively low. There are many factors affecting the Down’s syndrome screening value, and the results of fetal Down’s syndrome screening are not completely accurate, but only predict the risk of developing the disease. It is recommended that you should have a regular routine, take regular obstetric checkups, avoid strenuous labor, and eat a proper diet and nutrition. If you feel unwell, please consult a doctor and have the relevant tests done according to the doctor’s instructions.