What is the role of cell-free fetal DNA testing in prenatal screening of Down syndrome?

Updated: Apr 30, 2018
  • Author: Gratias Tom Mundakel, MBBS, DCH; Chief Editor: Maria Descartes, MD  more...
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Answer

Cell-free fetal DNA is composed of fragments of fetal DNA derived from the placenta that can be found in maternal plasma. The fragments can be seen in maternal circulation as early as 7 weeks' gestation and last throughout pregnancy, becoming undetectable in the maternal circulation a few hours after birth. The cell-free fetal DNA screening test can be done at any gestational age after 10 weeks and can detect about 99% of Down syndrome pregnancies. Adoption of cell-free DNA for screening women has been slow because of cost, but it is currently used at many centers for screening women at high risk for offspring with Down syndrome. Studies have shown that this test has a high sensitivity and specificity. [89, 90, 91, 92, 93, 94, 95]

A positive screening result with the above methods only suggests an increased risk for Down syndrome, and definitive testing with chorionic villus sampling or amniocentesis and chromosomal analysis is indicated.


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