If the non-invasive DNA screening is low-risk, but the ultrasound suggests abnormal fetal development, what should the mother do? At this point, the doctor suggested amniotic fluid test is not a bluff, in the end, is it necessary? In fact, through the previous reading, we know that “non-invasive DNA” screening is the number of chromosomes 21, 13 and 18. However, our genetic material “chromosomes” are actually 23 pairs in total, and these 23 pairs of chromosomes, which look like silkworms under a microscope, are highly precise! Each pair must have a number of 2, and each pair has a fixed structure. Therefore, “non-invasive DNA” screening only counts the baby’s chromosomes 21, 13 and 18, and is limited in what it can do. Therefore, in the industry standard for non-invasive screening, experts clearly tell us that amniotic fluid chromosome testing should be performed “if fetal imaging (including ultrasound, etc.) suspects microdeletion and microduplication or other chromosomal abnormalities in the fetus”.