To the Point- cfDNA started as a screening test for Down syndrome, but over the time the list of conditions for which it can screen for has grown.  Most labs routinely offer screening for Down syndrome, Trisomy 18 and Trisomy 13, at minimum.  These are all conditions that involve a whole extra chromosome and are referred to as aneuploidies. The next most common conditions screened for are sex chromosome conditions (X & Y chromosome variations).  Other less frequent aneuploidies that laboratories may screen for include triploidy (whole extra set of chromosomes), trisomy 16 and trisomy 22.  Recently, laboratories have started offering screening for a set of rare genetic conditions called microdeletion syndromes, which are the result of a missing piece of a chromosome.  Sometimes cfDNA will identify conditions in mom and/or baby that are not even on the list of conditions being screened.  cfDNA is always your choice; you can also be a part of the decision in terms of what conditions are screened for.  Talk to your provider about what conditions are screened for by the laboratory he/she uses.

Aneuploidies (extra or missing chromosome conditions)

Some labs offer screening for sex chromosome conditions (X & Y chromosome variations), including the following:

Additional aneuploidies that may be screened for that are more lab-dependent include the following:

  • Triploidy (a whole extra set of chromosomes, 69 total)
  • Trisomy 16
  • Trisomy 22

Microdeletion Syndromes

In addition to the conditions listed above, laboratories have started adding additional testing for conditions that involve changes, not in the total number of chromosomes, but differences in smaller parts of the chromosome (at the gene level). These conditions are called microdeletion conditions or syndromes. It is important to note that cfDNA labs vary in what microdeletion conditions they offer screening for. Also, most of these conditions are relatively rare, so the chance of an abnormal result being a true positive (the baby actually having the condition) for many of these conditions is relatively low.