It is necessary to have an amniocentesis if you have not passed the non-invasive. Non-invasive DNA testing is a test to determine the three major chromosomal disorders of Down syndrome, Edward’s syndrome, and Patau syndrome by drawing peripheral blood. It is mainly used for people who have a mother over 35 years old, have an ultrasound showing high risk of aneuploidy, have had a child with trisomy, and have a high risk of having a positive result for aneuploidy in early pregnancy, mid-pregnancy, triple screening, and quadruple screening. Although non-invasive DNA testing is more accurate, with an accuracy rate of more than 90%, it is not a confirmatory test, but only a screening tool. If the non-invasive DNA test shows high risk, amniocentesis or karyotyping or cord blood sampling is needed to rule out chromosomal disorders.