Non-invasive for non-invasive DNA, four-dimensional for four-dimensional ultrasound, non-invasive DNA low wind four-dimensional ultrasound when the embryo chromosome aspect is basically no problem, but it can not indicate that the fetal structure aspect is completely no problem. Non-invasive DNA low risk can not indicate that four-dimensional ultrasound must be no problem, non-invasive DNA is mainly check fetal chromosomes, 21, 18, 13 pairs of chromosomes of the fetus to check, is a hidden fetal malformation check, non-invasive DNA low risk indicates that fetal chromosomal abnormality occurs in a relatively low incidence of four-dimensional ultrasound is mainly to detect the structure of the fetus. Fetal four-dimensional ultrasound can clarify the fetal face, limbs, heart and other important organs with or without developmental malformations, fetal chromosomes and structure have a correlation, but also can be alone abnormalities, it is possible that the fetal genetic material is normal, but the structure of the structure has an abnormality. After the non-invasive DNA test it is still necessary to go for a 4D ultrasound test to be able to understand specifically how the embryo is developing in the womb.