Pregnant women undergoing Down’s syndrome screening do not need to fast, but it is recommended to fast for at least 8 hours to avoid dietary factors. The Down’s test is a screening test for fetal malformations, mainly for genetic disorders such as trisomy 21, trisomy 18 and optic neural tube defects. The biochemical test is usually performed by combining the general condition of the pregnant woman, such as her last menstrual period, height, weight and week of pregnancy, as well as whether she smokes, has diabetes or other factors to assess the probability of the fetus having Down’s syndrome. The main indicators are free beta-HCG and PAPP-A in the early stage and free beta-HCG, methemoglobin and free estriol in the middle stage, but it is recommended to fast for at least 8 hours to avoid the influence of dietary factors on these indicators. Down’s syndrome screening is usually performed at 16-18 weeks of gestation, and pregnant women and their families should keep track of the examination time.