analyses maternal blood for circulating cell free fetal DNA (ccffDNA) at 10 wk GA onwards. Requires dating ultrasound for accuracy
in high risk women (>age 35) highly sensitive for Trisomy 21(>99.5%), specificity (>99.8%)-can also look for trisomy 18, 13 and some X and Y disorders as well as common microdeletions
not harmful to the pregnancy, results available in 7-10 day
does not screen for oNTD
high cost to patient (only covered in some provinces in certain cases)
unclear how accurate yet in low risk women (<35)
need to confirm with invasive testing
Does not test for all aneuploidy