Cell-free fetal DNA testing, which measures the relative amount of free fetal DNA in a pregnant woman's blood, is a new screening test that indicates the risk of Down syndrome (trisomy 21), Edward syndrome (trisomy 18), and Patau syndrome (trisomy 13). A recent analysis of 37 published studies shows that the test can detect more than 99% of Down syndrome cases in singleton pregnancies, with a very low false positive rate of less than 0.1%. This makes it superior to all other testing methods.
The test is much less accurate for Edward syndrome and Patau syndrome, however, with respective detection rates of about 96% and 92% and a false positive rate of 0.26%. The analysis is published in Ultrasound in Obstetrics & Gynecology.