It makes sense to have non-invasive DNA done at the advanced age of 40 because the incidence of chromosomal developmental abnormalities in the fetus increases significantly with age. It is recommended that every pregnant woman over the age of 35 should have a non-invasive DNA test to detect chromosomal abnormalities in the fetus at an early stage. If there are chromosomal developmental abnormalities, most of the fetuses will have abnormal intellectual development after birth, which will cause serious burden to the family and society. Therefore, it is very meaningful to do this test.