Prenatal Cell-Free DNA Screening
Reviewed
A blood test during pregnancy that checks the baby's DNA in the mother's bloodstream to find out if the baby is more likely to have certain chromosome disorders, such as Down syndrome.
Preparation and collection
You may want to speak to a genetic counselor before getting tested to understand possible results and what they might mean.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- A cfDNA screening cannot tell you for sure whether your baby has a chromosome disorder; it only indicates risk.
- The screening is not as accurate if you are pregnant with more than one baby (twins, triplets, or more).
- False-positive and false-negative results are possible.
- Results must be interpreted by a healthcare professional; no reference intervals are provided.
What to do next
If your results are screen-positive, your provider will discuss confirmatory tests such as amniocentesis (usually done between weeks 15 and 20) or chorionic villus sampling (CVS, usually done between weeks 10 and 13). These tests have a slight risk of miscarriage. If you have questions about your results, talk to your provider and/or a genetic counselor.
Evidence source
U.S. National Library of Medicine: Prenatal Cell-Free DNA Screening