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For pregnant women, to assess the risk of your developing baby (fetus) having certain chromosome disorders
During or after the 10th week of pregnancy
A blood sample drawn from a vein in the mother's arm
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). Cell-free fetal DNA prenatal screening, called non-invasive prenatal screening (NIPS) by some, 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.
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 section of this article.
A blood sample is obtained by inserting a needle into a vein in the mother's arm.
No test preparation is needed.
The cell-free fetal DNA (cffDNA) test is a relatively new test that may be used to assess the risk of a pregnant woman's developing baby (fetus) having a chromosome disorder, such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), or Patau syndrome (trisomy 13). It may be used to identify other rare conditions resulting from an extra chromosome or missing piece of chromosome (microdeletion).
Non-invasive prenatal screening (NIPS) that uses cffDNA testing is one of the options that may be offered for prenatal screening for chromosome disorders. Conventional testing options include the first trimester Down syndrome screen and the second trimester maternal serum screen. The screening approach a woman chooses depends on what technology is available and when she first seeks prenatal care. Also, pregnant women may wish to check with their insurance companies, as not all policies may cover cffDNA.
Currently, two major health organizations differ in their recommendations on the use of cffDNA testing. Talk to your healthcare practitioner about your prenatal screening options and what may be best for you.
The cffDNA test is used as a screening test, not a diagnostic test. If there are abnormal findings in routine prenatal testing or in cffDNA testing, then more invasive confirmatory testing using procedures such as chorionic villus sampling (CVS) or amniocentesis may be indicated to diagnose a chromosome abnormality.
The cell-free fetal DNA test may be offered during or after the tenth week of pregnancy and after pre-test genetic counseling.
A negative cffDNA test result means that it is very unlikely that the baby has trisomy 13, 18, or 21. If the test is negative for other chromosomal abnormalities that the laboratory tested for, then it is unlikely that the baby is affected by those. However, these trisomies or genetic defects cannot be entirely ruled out, and other chromosome abnormalities could still be present.
If a cffDNA screen is positive, then the fetus is at an increased risk of having the identified abnormality. However, the test is not diagnostic. The performance of more invasive procedures, including chorionic villus sampling (CVS) between the tenth and twelfth week of pregnancy or an amniocentesis procedure between 15 and 20 weeks of pregnancy, and subsequent chromosome analysis is required to rule out or diagnose a chromosome disorder.
In some cases, the laboratory that performs the DNA analysis will return an "indeterminate" or "no call" result when there is an insufficient amount of cell-free fetal DNA in the maternal blood sample. This can occur, for example, when the woman is obese (weighing more than 250 pounds) or when the blood sample is collected too early in the pregnancy (prior to the tenth week of pregnancy). ACMG and ACOG recommend that women with a "no call" result be offered diagnostic testing using amniocentesis or CVS if the maternal blood sample was drawn at an appropriate gestational age. ACMG also recommends offering a screening test other than NIPS in cases of significant maternal obesity.
Questions on interpreting the results of a cffDNA are usually best answered by someone experienced in genetic counseling.
The full clinical utility of cffDNA testing has yet to be established. As research progresses, use of the test may be expanded.
You may choose to discuss this screening option as well as others with your healthcare practitioner to make an informed decision. You may also be referred to a genetic counselor who will help you understand the limitations and benefits of screening as well as the meaning and implications of your results.
Yes, you may be offered the test with subsequent pregnancies. Since it is the baby that is being assessed, each pregnancy would be tested and evaluated separately.
This depends on the laboratory performing the test. It may take one to two weeks for results.
No. CffDNA does not detect neural tube defects. To screen for these disorders, you may have a different test done in the second trimester called the alpha-fetoprotein (AFP) maternal screen. To learn more, read the article on Second Trimester Maternal Serum Screen.
Yes, this test can reveal the sex of your baby and your healthcare practitioner may provide you with this information if you request it. However, if you don't want to know the sex of your baby, you can usually request that this information be suppressed in the report.
Sources Used in Current Review
Gregg AR, Skotko, BG, Bekendorf JL, et al. Noninvasive Prenatal Screening for Fetal Aneuploidy, 2016 Update: A Position Statement of the American College of Medical Genetics and Genomics. Genetics In Medicine. Published online 28 July 2016. Available online at http://www.nature.com/gim/journal/vaop/ncurrent/full/gim201697a.html. Accessed January 10, 2017.
Genetic Support Foundation. Cell-free DNA (cfDNA) Screening. Available online at https://www.geneticsupportfoundation.org/genetics-and-you/pregnancy-and-genetics/pregnancy-and-genetics-tests/cell-free-dna-cfdna. Accessed January 2017.
(September 2016) American College of Obstetricians and Gynecologists. Prenatal Genetic Screening Tests. Available online at http://www.acog.org/Patients/FAQs/Prenatal-Genetic-Screening-Tests?IsMobileSet=false. Accessed January 2017.
(©2017) Cell-Free DNA Prenatal Screen. Mayo Medical Laboratories. Available online at http://www.mayomedicallaboratories.com/test-catalog/Specimen/63439. Accessed January 2017.
(September 2015) American College of Obstetricians and Gynecologists. Committee on Genetics Society for Maternal–Fetal Medicine, Committee Opinion No. 640. Available online at http://www.acog.org/Resources-And-Publications/Committee-Opinions/Committee-on-Genetics/Cell-free-DNA-Screening-for-Fetal-Aneuploidy. Accessed January 2017.
(September 2016) Prenatal Genetic Screening Tests. American Congress of Obstetricians and Gynecologists. Available online at http://www.acog.org/Patients/FAQs/Prenatal-Genetic-Screening-Tests?IsMobileSet=false. Accessed January 2017.
Sources Used in Previous Reviews
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Lewis, R. (2014 March 8). Fetal DNA Testing for Low-Risk Women Gets Mixed Reviews. Medscape Medical News [On-line information]. Available online at http://www.medscape.com/viewarticle/821690. Accessed March 2014.
(2014 March). Non-invasive Prenatal Testing for Chromosomal Abnormality using Maternal Plasma DNA. Royal College of Obstetricians and Gynaecologists Scientific Impact Paper No. 15 [On-line information]. Available online at http://www.rcog.org.uk/files/rcog-corp/SIP_15_04032014.pdf. Accessed March 2014.
(2014 March 5). SMFM Physicians Recommend NIPT for High-Risk Patients. Smfm Newsroom [On-line information]. Available online at http://www.smfmnewsroom.org/2014/03/smfm-physicians-recommend-nipt-for-high-risk-patients/. Accessed March 2014.
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