Non-invasive DNA during pregnancy can be done between 15 and 20 weeks of pregnancy. Early or late testing may affect the accuracy of the test results. Non-invasive DNA belongs to a kind of prenatal examination, is through the pregnant woman’s vein blood, gestational week, age, weight comprehensive to screen whether the fetus has chromosomal abnormality and other related diseases risk, such as Down’s syndrome. Non-invasive DNA accuracy rate is only 90% or more, if the DNA test results for high risk, it is necessary to further amniocentesis, the extraction of amniotic fluid for direct analysis to determine the diagnosis. In addition, to go to the hospital for blood test, you should eat less spicy and stimulating food a few days before to avoid abdominal discomfort. It is recommended to fully communicate with the doctor before the test to understand the precautions and follow the doctor’s instructions for preparation.