The method described in the literature as fetal DNA, extracellular DNA, or non-invasive prenatal diagnosis from maternal blood is currently one of the most advanced in medical science. During normal pregnancy, some cells belonging to the fetus (the unborn child in the womb) enter the mother’s bloodstream. These cells have also been shown to remain in some maternal tissues (such as the thymus gland) for extended periods. In addition to these fetal cells, there is also DNA called extracellular DNA, which is passed from the fetus to the mother’s bloodstream. When these DNA fractions are detected, it is possible to investigate the presence of certain genetic diseases of the fetus, primarily trisomy. As for trisomy (Down syndrome and other trisomy diseases), it should be remembered that the result of a mother’s blood test with such a test is not an exact answer about whether trisomy is in the fetus, but a forecast of the likelihood of this ailment. In other words, this test is not a diagnostic test for fetal trisomy. For these reasons, if the test shows a low probability, it does not mean that the fetus does not have trisomy but simply indicates that the risk of its occurrence is very low. In cases where the test shows a high probability, you should resort to more detailed studies of the fetus.