At present, Down’s syndrome screening is a routine test for almost every pregnant woman of low maternal age, and pregnant women are generally aware of the importance of this test and often take the initiative to mention it to their doctors. However, when they get the test results, they often don’t understand the content of the test very well, especially when there is a high risk of screening, but also anxiously at a loss, do not know what to do, and some may even be worried because of the doctor’s improper explanation, and sometimes cry. First of all, strictly speaking, Down’s syndrome screening should be called serological screening for pregnant women, Down’s syndrome screening is a simplified term. This test is aimed at pregnant women under 35 years of age and is designed to check for the risk of Down syndrome, trisomy 18 and neural tube defects in the fetus. Because the test is a risk rate, it is not a confirmatory test and the results obtained are only predictive of a high or low risk of developing the disease. For those at high risk, other methods that can confirm the disease are needed to confirm or exclude it. Therefore, there is absolutely no need to make a fuss about abnormal test results when you get a Down’s syndrome screening test result. So, why do we need to do Down’s syndrome screening? It’s actually a policy of eugenics. It is to detect as many critical and common diseases as possible in the population of all pregnant women before the birth of the fetus to achieve the purpose of eugenics. Because Down syndrome is the most common mental retardation malformation, it is listed as a priority disease for prenatal screening. Prenatal diagnosis of the disease requires amniocentesis or cord blood puncture to obtain fetal cells for chromosomal examination to confirm the diagnosis. This method is invasive and has the potential to cause complications such as miscarriage, so if all pregnant women were to undergo prenatal testing for Down syndrome in this way, the number of complications such as miscarriage would increase, especially for those with normal pregnancies, and the side effects would clearly outweigh the costs. It is in this context that Down’s syndrome screening is applied, as it can be performed by drawing the peripheral blood of the pregnant woman without any side effects, and its safety can be imagined. So, is Down’s syndrome screening necessarily better than invasive chromosome testing? The answer is no. Down’s syndrome screening only screens out high-risk fetuses, but the diagnosis must be confirmed by invasive chromosomal testing. In general, only about 2% of screened fetuses with high risk are diagnosed with Down’s syndrome. Similarly, there is a very low chance that a fetus with Down’s syndrome will be missed by screening, i.e., that a fetus with Down’s syndrome will be screened as low risk. As you know, the main screening test is for Down syndrome, which is why the serologic screening of pregnant women is called Down syndrome screening. There is also screening for another chromosomal disorder, but with a much lower prevalence than Down syndrome, trisomy 18. As well as assessing the risk of developing neural tube defects based on methotrexate values. Screening for Down syndrome as well as trisomy 18 for those at high risk requires fetal chromosomal testing to confirm the diagnosis, while those at high risk for neural tube defects are primarily diagnosed by ultrasound.