Prenatal Cell-Free DNA Screening

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. 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.

Chromosomes are tiny 'packages' in your cells that contain your genes. Genes carry information, called DNA, that controls what you look like and how your body works. Normally, you're born with a set of 46 chromosomes in each cell.

The chromosomes are grouped into 23 pairs. Each pair has two chromosomes, one coming from each parent.; If one of these pairs has an extra copy of a chromosome, it's called a trisomy. A trisomy causes changes in the way the body and brain develop.; If there is an extra copy of chromosome 21, it's called Down syndrome.

This is also known as trisomy 21. Down syndrome is the most common chromosome disorder in the United States.; Other trisomy disorders include Edwards syndrome (trisomy 18), where there is an extra copy of chromosome 18, and Patau syndrome (trisomy 13), where there is an extra copy of chromosome 13. These disorders are rare but more serious than Down syndrome.

Most babies with trisomy 18 or trisomy 13 die within the first year of life.; There is very little risk to you and your baby with a cfDNA screening. But a cfDNA screening can't tell you for sure whether your baby has a chromosome disorder. Your health care provider will need to order other tests to confirm or rule out a diagnosis.

Why this test is done

Many providers recommend this screening if you are pregnant and are at a higher risk of having a baby with a chromosome disorder. You may be at higher risk if:

• You are age 35 or older. The mother's age is the main risk factor for having a baby with Down syndrome or other trisomy disorders. The risk increases as you get older.
• You've had another baby with a chromosome disorder.
• Your fetal ultrasound didn't look normal.
• Other prenatal test results were not normal.

Many providers recommend screening if you are pregnant even if you aren't at higher risk of having a baby with a chromosome disorder. This is because the screening has almost no risk and has a high rate of accuracy.

You and your provider should discuss if a cfDNA screening is right for you.

How to prepare

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. He or she can explain the possible results and what they might mean to you and your baby.

Sample type

Blood

Other names for this test

cell-free fetal DNA, cffDNA, non-invasive prenatal tet, NIPT, non-invasive prenatal screening, NIPS