This document discusses prenatal testing for fetal chromosomal abnormalities like Down syndrome, Edwards syndrome, and Patau syndrome. It provides information on the prevalence of these disorders, describes routine prenatal diagnostic methods including invasive and non-invasive options, and examines a new non-invasive prenatal diagnosis technique using cell-free fetal DNA from maternal blood. The document presents several clinical cases demonstrating the accuracy of this non-invasive prenatal testing and its advantages over other options.