Fetal non-invasive DNA testing is a test that detects whether a fetus, has a chromosomal abnormality by drawing venous blood from a pregnant woman and performing laboratory tests. The overall procedure is as follows: 1. Time. The time to perform the fetal non-invasive DNA test is usually at least 12 weeks of pregnancy, preferably between 12 and 22 weeks of pregnancy.2. It is not necessary to be absolutely fasting when doing the non-invasive DNA test because the fetal DNA fragments in the blood of the pregnant woman are not disturbed by dietary factors.3. -Trisomy 21, trisomy 21 and other chromosomal abnormalities. 4. Non-invasive DNA testing should not be done if you are less than 12 weeks pregnant, and should be postponed if you are pregnant with a cold.