For some conditions, particularly Down syndrome, cfDNA has been shown to be a more accurate screening test than traditional screening tests. cfDNA may also potentially screen for more chromosome conditions than traditional testing.
However, traditional screening can assess for conditions that would not be found with cfDNA screening, such as open neural tube defects (ONTDs). Traditional screening tests can also detect an increased risk for pregnancy complications, such as preeclampsia, preterm labor, and growth restriction.
cfDNA has the benefit of being able to be done sooner in pregnancy, often as early as 10 weeks. cfDNA is also able to test for sex as well as sex chromosome differences (more or fewer X or Y chromosomes than expected). Some labs offer screening for other genetic conditions, such as microdeletion syndromes, for which there is limited available data.
It is important to discuss with your provider what your cfDNA test will screen for, and to come to a plan that is best for you and your family.
Both cfDNA and traditional screening tests have the possibility of a false positive or false negative result. A false positive result is when a test comes back high risk for a condition, such as trisomy 18, but the pregnancy does not actually have trisomy 18. On the other end, a false negative result is when a test comes back negative for a condition but the pregnancy actually has the condition.
Currently, cfDNA is not regulated by the FDA. It is also important to note that much of the information available regarding how reliable this test is comes from studies funded by the commercial labs and/or authored by individuals associated with one of the commercial labs.
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