Conclusion

The findings of this systematic review demonstrate that there is extensive evidence supporting the use of cffDNA for prenatal screening of the common autosomal trisomies (T21-T18-T13) and SCAs, in singleton pregnancies. Amongst the autosomal trisomies, T21 had the highest results, whereas T13 had the lowest ones. As for SCAs, its accuracy needs to be greatly improved, especially for 45,X0. However, it is a screening test and not a diagnostic test, hence, all positive cffDNA results should be followed by a confirmatory procedure, as false positives can occur. Similarly, a negative result does not discard an aneuploidy, as false negatives can also occur. Finally, the main reason for false results is placental mosaicism, and the main cause of no-call results is an insufficient fraction of cffDNA.