Cell-Free Fetal DNA (cffDNA)
Definition - What does Cell-Free Fetal DNA (cffDNA) mean?
Cell-free fetal DNA (cffDNA) is the DNA of the developing baby (fetus) that circulates in the mother’s bloodstream. The cffDNA stems from the cells of the outer layer of the developing embryo known as the trophoblast that will develop into a placenta. CffDNA analysis is a noninvasive test done in pregnant women to screen the fetus for certain chromosomal abnormalities. The woman should be at least 10 weeks pregnant to be considered for this test.
FertilitySmarts explains Cell-Free Fetal DNA (cffDNA)
To perform a cffDNA test, DNA from the mother and fetus is extracted and screened from a blood sample drawn from the mother.
The cell-free fetal DNA evaluates the risk for specific chromosomal disorders like Down syndrome, trisomy 13, and trisomy 18. The test is recommended in women at increased risk for genetic problems. These women include:
- Age 35 years or older
- Women with ultrasound findings demonstrating an increased risk of chromosomal abnormality in the fetus
- Women with a prior history of births with genetic problems
- Either partner carrying a balanced Robertsonian translocation associated with trisomy 13 or trisomy 21
- Women with first-trimester or second-trimester screening results suggestive of a chromosomal abnormality
The cffDNA test can also help determine the fetal sex and rhesus (Rh) blood type.
The cffDNA test has certain limitations. It can be falsely positive even in the absence of a chromosomal disorder in certain conditions such as:
- Cancer in the mother
- Chromosomal duplication in the mother
- Multiple pregnancies
- Use of a donated egg
Similarly, a negative cffDNA test result does not necessarily indicate the absence of a genetic abnormality. Moreover, the fetal DNA is swamped by the presence of cell-free DNA of the mother, which reduces the fraction of fetal DNA. For accurate results from cffDNA testing, the fetal fraction should exceed 4%. The test would otherwise yield "uninterpretable” test results despite the woman carrying a higher risk for a chromosomal abnormality.
Physicians also offer another blood test called alpha-fetoprotein or an ultrasound for risk assessment in women undergoing cffDNA testing.