Women of childbearing age need to undergo a Down’s syndrome test at about 15-20 weeks of gestation. The test costs about$250 and up and is mainly to check for congenital stupidity, neural tube defects, and the presence of trisomy 21, or 21-trimester chromosome syndrome, which is a hereditary disease that is very important for the health of the fetus. Early detection of these genetic disorders in the fetus will allow for early management. If not screened out, the birth of a child may cause great harm to society and the family, so the Down’s syndrome has been one of the normal maternal screening program, just like doing glucose tolerance, to a certain time should go to do, to avoid the occurrence of some unnecessary adverse results.