Pregnant women have fetal DNA in their blood because blood is exchanged between the fetus and the mother through the placenta. A pregnant woman’s blood contains free DNA from the fetus because the circulation of the fetus is exchanged with the mother through the placenta. Non-invasive DNA is an important method of prenatal screening to determine the likelihood of chromosomal abnormalities in the fetus. A woman can usually have a non-invasive DNA test between 15 and 23 weeks of pregnancy, which can determine if the fetus has Trisomy 21-Trisomy, Trisomy 18-Trisomy, and so on. This test involves taking a pregnant woman’s blood and then extracting fetal free DNA from her plasma for testing. Pregnant women should pay attention to the prenatal checkups during pregnancy, and actively listen to the professional doctor’s advice to do comprehensive care and health care work, which can effectively ensure the safety of delivery. During pregnancy, pay attention to rest more, at the same time should relax, avoid tension, anxiety, any discomfort should be timely to the hospital, the doctor clear diagnosis, and cooperate with the doctor to deal with the symptoms.