Background: Down syndrome is a hereditary disease that is often screened before birth. If not diagnosed and treated in time, it will bring a huge burden to the child and family. Screening for Down syndrome mainly uses serum markers and ultrasound measurements in the blood of pregnant women to determine the risk of the disease. In the medical field, detection accuracy has always been one of the important indicators for evaluating the quality of a detection method. Therefore, assessing the accuracy of Down syndrome screening capabilities is of great significance to guide clinical diagnosis. Accuracy of Down\’s syndrome screening Down\’s syndrome screening is a non-invasive testing method that mainly detects two types of DNA in the blood of pregnant women