It is recommended to do both Early and Middle Down screening, Early Down screening can check the condition of the fetus earlier, and terminate the pregnancy as early as possible if the fetus may suffer from Down’s syndrome, if you miss Early Down screening or your hospital does not have Early Down screening, you can also do Middle Down screening only. Early Down refers to early pregnancy Down screening, which is conducted in early pregnancy, and mid Down refers to mid pregnancy Down screening, which is conducted in 15-20 weeks of pregnancy. Early Down screening mainly does pregnancy-related protein tests, while mid-term Down screening has more tests, such as human chorionic gonadotropin, anti-perinuclear factor, free estriol and other tests. Early Down screening can check whether the fetus has any chromosomal abnormality as early as possible, while mid-Thomas screening can check the condition of the fetus more comprehensively, so it is better to do both. However, at present, some hospitals do not provide Early Down’s test. If Early Down’s test is not available, Intermediate Down’s screening is also available.