It is important to pay attention to it, but do not worry too much. The screening test is short for prenatal screening for Down’s syndrome. An abnormal result means that the fetus has a higher risk of Down’s syndrome and should undergo further confirmatory tests such as amniocentesis and chorionic villus testing. Sometimes the first screening test result is abnormal and the second test is normal. This test takes the mother’s venous blood and measures the serum values of chorionic gonadotropin (HCG), free estriol (FE3), and alpha-fetoprotein (AFP), along with the maternal indicators (age, week of pregnancy, weight, menstrual cycle, other medical history, etc.) to determine the probability of the fetus having trisomy 21.