Analysis of cell free fetal DNA (cffDNA) in maternal plasma provides the 
opportunity for reliable, timely, safe and cost-effective diagnosis of single 
gene disorders. The detection of certain fetal loci using cffDNA and 
conventional molecular analytic approaches is possible from 4 weeks gestation. 
To date, non-invasive first-trimester analysis for single gene disorders has 
been limited by assay sensitivity and specificity, due to the background 
maternal DNA. The anticipated ability to enrich the fetal component of cell free 
DNA will increase the robustness of tests and permit semi-quantitative analysis, 
broadening the scope of testing to include recessive disorders such as cystic 
fibrosis. Testing for large-scale mutations might remain limited by the 
fragmented nature of cffDNA and, when testing very early in gestation, careful 
ultrasound examination will be needed to determine the number of gestational 
sacs, because of the risk of discordant twin pregnancies.