Both non-invasive prenatal genetic testing and Down’s syndrome screening are prenatal tests primarily used to prevent Down’s syndrome. Down syndrome is the most common disorder causing mental retardation and the most common disorder caused by defects in genetic material, with an overall incidence of about 1 in 700. More importantly, the occurrence of Down syndrome is completely random and every pregnant woman is at risk of having a child with Down syndrome. Therefore, the appropriate population for both non-invasive prenatal genetic testing and Down’s syndrome screening are pregnant women with normal pregnancies. Down’s syndrome screening is currently the most widely used prenatal screening test for Down’s syndrome. It is simple, inexpensive, and has a long history of clinical practice. The main problems with Down’s syndrome screening are the relatively high rate of missed tests and the low specificity of the test. The detection rate of Down’s syndrome is about 30%, and the specificity of Down’s syndrome is about 1-2%. Noninvasive prenatal genetic testing has the same purpose as Down’s syndrome screening and is a screening method primarily used to prevent Down’s syndrome. However, non-invasive prenatal genetic testing is superior to Down’s syndrome screening in terms of accuracy. The rate of missed tests for Down’s syndrome is only about 2%, while the specificity is about 99%. Non-invasive prenatal genetic testing is a far superior method to Down’s syndrome screening in terms of accuracy. Compared to Down’s screening, its main shortcomings are that it is more expensive and its clinical use is short-lived, and long-term results need to be observed. The main differences between non-invasive prenatal genetic testing and Down’s screening Let’s make a specific hypothesis about the differences between non-invasive prenatal genetic testing and Down’s screening. Assuming that the detection rate of Down’s syndrome is 70%, if you are screened for Down’s syndrome, the probability of your child having Down’s syndrome will be reduced from 1/700 to 1/2333, i.e. to 1/3.3. This is the point of existence of Down’s syndrome screening. For non-invasive prenatal genetic testing, assuming that the detection rate for Down’s syndrome is about 99%, if you get a normal result from a non-invasive prenatal genetic test, the probability of your child having Down’s syndrome will be reduced from 1/700 to 1/70000, i.e., to 1/100. For every 100 fetuses with Down’s syndrome, NICNCT detects 99, while Down’s syndrome screening detects about 70. When specificity is taken into account, the specificity of the non-invasive prenatal genetic test is over 99%, meaning that 99 out of 100 pregnant women who are determined to be at high risk by the non-invasive prenatal genetic test are indeed carrying a child with Down syndrome. In contrast, the specificity of Down’s syndrome screening is about 1-2%, meaning that only 1-2 out of every 100 pregnant women with a high risk of Down’s syndrome are actually carrying a child with Down’s syndrome. Therefore, compared to non-invasive prenatal genetic testing, Down’s syndrome screening results in a large number of false positives, and the psychological burden on these pregnant women is considerable along with the actual risk of amniocentesis. If analyzed purely on technical grounds, non-invasive prenatal genetic testing is clearly a suitable and highly accurate screening method to replace Down’s syndrome screening. Non-invasive prenatal genetic testing is recommended as an alternative to Down’s syndrome screening for pregnant women who are financially able to do so.