Peripheral blood chromosome testing, also known as non-invasive DNA testing, or non-invasive prenatal genetic sequencing, involves the collection of the mother’s peripheral blood to test for fetal genes. Because recent studies have found the presence of fetal free DNA fragments in the mother’s blood, the number of free DNA fragments from chromosome 21 is significantly higher in mothers of children with trisomy 21, also known as Down syndrome, than in normal pregnant women. Similarly, this method is also suitable for detecting trisomy 18 and trisomy 13. Non-invasive DNA testing is done after 12 weeks of gestation. Non-invasive here refers to the previous screening for Down’s syndrome, and if it is a high risk after which an amniocentesis is required to confirm the diagnosis and make a validated diagnosis. Amniocentesis is an invasive test, and the use of new peripheral blood for genetic testing is a non-invasive test.