At a Glance
Why Get Tested?
To assess the risk of a pregnant woman's developing baby (fetus) having certain chromosome disorders; it is currently recommended for women at high risk of having babies with these disorders.
When to Get Tested?
During or after the 10th week of pregnancy when your health practitioner has determined that you are at an increased risk of having a baby with chromosomal abnormalities
A blood sample drawn from a vein in the mother's arm
Test Preparation Needed?
The Test Sample
What is being tested?
Cell-free fetal DNA (cffDNA) is genetic material that is released by the placenta and circulates in a woman's blood during pregnancy. CffDNA generally reflects the genetic makeup of the developing baby (fetus). The technology employed in this test detects defects in fetal DNA after it is purified from the pregnant woman's blood.
CffDNA is present in a pregnant woman's blood in small quantities starting in the first trimester and increases throughout pregnancy. The cffDNA test is a relatively new, non-invasive method of screening that can be performed as early as the tenth week of pregnancy for women who are at an increased risk of having a baby with certain chromosome abnormalities.
The test can identify chromosome disorders in a developing baby, including the presence of extra chromosomes (trisomies) such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13). The extra genetic material present in these conditions affects the development of the baby and causes characteristic signs, symptoms, and complications.
Down syndrome is the most common of the three trisomies detected by cffDNA testing and varies significantly in severity from person to person. Edwards syndrome and Patau syndrome are more rare and more severe, with most affected babies dying within weeks to months of birth. This test may be used to identify other rare conditions resulting from an extra chromosome or missing piece of chromosome (microdeletion).
CffDNA testing can also detect an extra sex chromosome. One example is Klinefelter syndrome, resulting from two X chromosomes and one Y chromosome. For more on this and other rare chromosome disorders, see the Related Pages tab.
Current routine prenatal testing includes the first trimester Down syndrome screen and the second trimester maternal serum screen. Studies have shown that the cffDNA test can be more specific and sensitive than these routine tests in high-risk women.
The American College of Obstetricians and Gynecologists (ACOG) currently recommends that the cffDNA test be offered to women at an increased risk for fetal defects after genetic counseling. However, it recommends that the test be offered separately, not incorporated into routine prenatal testing. The routine second trimester maternal serum screen detects neural tube defects as well as chromosome disorders. Research is continuing into cffDNA's use as a general screen for women at average risk.
It is important to keep in mind that the cffDNA test is a screening test, not a diagnostic test. If there are abnormal findings in routine prenatal testing or in cffDNA testing, then more invasive testing, including chorionic villus sampling (CVS) between the tenth and twelfth week of pregnancy or an amniocentesis procedure between 15 and 20 weeks of gestation may be indicated to diagnose a chromosomal abnormality.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the mother's arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
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