If the first Down screening result is abnormal, it is not recommended to have another general Down screening review, that is, it is not recommended to have the Down screening twice. Because the screening rate of general Down’s syndrome screening is only about 60%, there is a great uncertainty in the screening rate itself. If the Down’s screening test is done twice, the two screening levels are parallel and the screening rate is not increased, so even if the results of the two screenings are inconsistent, it is not possible to make a scientifically accurate interpretation of the abnormal screening results. When the Down’s syndrome screening result is abnormal, you should choose non-invasive prenatal DNA screening or amniocentesis to further confirm the diagnosis according to the specific situation, such as the age of the pregnant woman and the risk cut-off value of Down’s syndrome screening.