Cell-Free DNA Testing
What is Cell-Free DNA Testing?
Cell-free DNA testing is a blood test used for pregnant women who are recommended to have a fetal DNA test because their pregnancy has an elevated risk for birth defects.
What is the Benefit of Cell-Free DNA Testing?
Cell-free DNA testing, a blood draw from the patient that carries no risk to the pregnancy and minimal pain, is an alternative to the earlier forms of fetal DNA testing, such as the amniocentesis test that involves a chance of pregnancy loss and a six-inch needle injected through the abdomen. Because of the cell-free DNA testing option, more pregnant women are participating in recommended testing for genetic abnormalities that would otherwise forgo amniocentesis testing.
Who Should Have a Cell-Free DNA Test?
Because older age increases chances of genetic disorders, all pregnant women over age 35 should be offered prenatal DNA testing, as well as women with a family history of a child with a genetic condition, women whose ultrasound indicates an abnormality such as Down syndrome, and women with abnormal blood screens.
About Cell-Free DNA Testing
This form of fetal testing, which many women are not familiar with, is an important advancement that detects the most common chromosomal problems in the first trimester blood draw. Cell-free DNA testing may replace amniocentesis as a screening test. Cell-free DNA testing removes the difficult decision for expectant mothers about whether to undergo a very invasive test like amniocentesis and its 1 in 300 risk of pregnancy loss.
Cell-free DNA testing was developed in 1997 after scientists discovered that fetal DNA appeared in the mother’s blood, making it possible for a simple blood draw to test for genetic disorders. Previously, amniocentesis was necessary to draw amniotic fluid cells from around the fetus to obtain its DNA. Cell-free DNA testing is also referred to as noninvasive prenatal testing.
One in 200 pregnancies involve genetic disorders and age increases those chances, with a 40-year-old woman facing a 1 in 40 risk. Some genetic disorders are catastrophic such as Trisomy 13 or 18, in which an extra copy of chromosome number 13 or 18 means the baby is not likely to survive.
Forewarned of such issues, a woman can plan for her Down syndrome (Trisomy 21) child’s upbringing. Women may also consider terminating the pregnancy if it involves Trisomy 13, 18 or 21.
Though results of the cell-free DNA test are highly accurate, women who receive a positive test result are advised to undergo amniocentesis or chorionic villus sampling, which are slightly more accurate and test for all 46 chromosomes. Current cell-free fetal DNA testing only detects eight chromosome problems, including sex chromosome issues such as Turner syndrome.
However, cell-free fetal DNA testing is advancing rapidly and has the potential to detect issues in all 46 chromosomes.
The American College of Obstetricians and Gynecologists and the National Society of Genetic Counselors support cell-free DNA testing as an option for women with pregnancies at elevated risk for certain chromosomal abnormalities.