Prenatal Cell-Free DNA Screening
Reviewed
Also called: Cell-Free Fetal DNA, cffDNA, Non-Invasive Prenatal Test, NIPT, Non-Invasive Prenatal Screening, NIPS
Prenatal cell-free DNA (cfDNA) screening is a blood test given during pregnancy. During pregnancy, some of the fetus's DNA circulates in the mother's bloodstream.
Specimen: Blood
Why this test may be ordered
- To screen for an increased risk of Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), or Patau syndrome (trisomy 13)
- To determine the baby's sex, especially if an ultrasound shows unclear genitals
- To check the baby's Rh blood type if the mother is Rh negative
Preparation and collection
You may want to speak to a genetic counselor before you get tested. A genetic counselor is a specially trained professional in genetics and genetic testing.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. This usually takes less than five minutes.
There is no risk to your unborn baby and very little risk to you. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
A cfDNA screening checks this DNA to find out if the baby is more likely to have certain conditions caused by an abnormal number of chromosomes, such as Down syndrome.
- Negative (lower likelihood): If your results were negative, it's unlikely that your baby has Down syndrome or another trisomy disorder. Limitation: cfDNA screenings are not as accurate if you are pregnant with more than one baby. Next step: If you have questions about your results, talk to your provider and/or a genetic counselor.
- Positive (higher likelihood): If your results were positive, it means there is an increased risk that your baby has one of these disorders. Limitation: But it can't tell you for sure if your baby is affected. Next step: To confirm a diagnosis, you'll need other tests, such as amniocentesis and chorionic villus sampling (CVS). These tests are usually very safe procedures, but they do have a slight risk of causing a miscarriage.
- A cfDNA screening cannot tell you for sure whether your baby has a chromosome disorder; it only indicates risk.
- The screening is not as accurate if you are pregnant with more than one baby (twins, triplets, or more).
- False-positive and false-negative results are possible.
- Results must be interpreted by a healthcare professional; no reference intervals are provided.
What to do next
If you have questions about your results, talk to your provider and/or a genetic counselor.
- What does a screen-positive result mean for my baby and my pregnancy?
- What are the risks and benefits of confirmatory tests like amniocentesis or CVS?
- How accurate is this screening for the conditions being tested?
- Should I meet with a genetic counselor to discuss my results?
- What follow-up care or monitoring will I need based on my results?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Prenatal Cell-Free DNA Screening