Cell-Free DNA Screening During Pregnancy

Posted On: September 21, 2017 By CIW

What is Cell-Free DNA Screening?

Cell-free DNA or cfDNA, refers to the fragments of fetal DNA found in the mother’s blood during a pregnancy. cfDNA is particularly helpful in conducting tests regarding the developing fetus during pregnancies in a minimally invasive way. The majority of the cfDNA found in the blood comes from the placenta and can be used to screen for chromosome disorders and other genetic conditions during the gestation period.

What Does cfDNA Test For?

Cell-Free DNA screening can help determine if there are any chromosomal irregularities in the fetus, as well as test for other genetic conditions. Today, we will discuss the chromosomal irregularities that typically consist of having one too many or too few chromosomes.

Trisomy 21, 18 & 13

Trisomy 21 is the most common of the chromosome disorders, involving one whole extra chromosome. This brings the total amount of chromosomes up to 21, hence the name trisomy 21. Trisomy 21 is more commonly known as Down Syndrome. Down Syndrome is a type of an inherited intellectual disorder and can also be associated with other health issues. cfDNA can also test for trisomy 18 and 13, along with other missing or extra genetic material.

cfDNA Screening Accuracy and Results

Cell-free DNA screening is not the most accurate of tests. This is due to a variety of factors that depend mainly on a woman’s baseline risk and age at the time of the test. One’s risk of having a child diagnosed with trisomy is greater at 40 than it would be for someone ten years younger. At 40 years of age, the chances of a woman giving birth to a child with trisomy are 1 of 100. However, for a woman at the age of 30, the chance about 1 in 1,000. Therefore, this test is known to be more accurate in women over 35 and less accurate with the potential of a false-positive result in younger women.

That is why it is very important to note that, just because a cfDNA test might show a positive result, it does not mean that your baby has a chromosome disorder. If you are pregnant and have any concerns about your risk of having a child with a chromosome disorder, contact your fetal medicine specialist for more information.


Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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