The best time to have Down’s syndrome screening is between 15 and 20 weeks of pregnancy. If the test result is low risk, the probability of having Down’s syndrome is low and there is no need to do a non-invasive DNA test. If the test result is high risk, it means that the probability of having Down’s syndrome is relatively high, so you need to follow the doctor’s instruction to do non-invasive DNA test or amniocentesis to confirm whether you have Down’s syndrome, and after the diagnosis, you should cooperate with the doctor to terminate the pregnancy as soon as possible. Even if the result of the Down’s syndrome test is high risk, there are many cases where it is normal to have a non-invasive DNA test again. Women who are pregnant after the age of 35 are at high risk and need to undergo invasive DNA screening or amniocentesis.