A genetic blood test for a baby, often done prenatally, analyzes the baby's DNA to identify the risk of certain genetic conditions.
Prenatal Cell-Free DNA Screening
One common type of genetic blood test is called prenatal cell-free DNA screening. This non-invasive test is performed on the pregnant person's blood and analyzes fragments of the baby's DNA that are circulating in the bloodstream. It's important to remember that this is a screening test, not a diagnostic test. A positive result indicates an increased risk and would typically be followed up with a diagnostic test like amniocentesis or chorionic villus sampling (CVS).
When can it be done?
This screening can be done in any trimester of the pregnancy.
What does it look for?
The test screens for:
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An increased risk of specific genetic conditions. Examples include:
- Down syndrome (Trisomy 21)
- Trisomy 18
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The baby's sex (if desired).
How does it work?
The test analyzes cell-free DNA (cfDNA) in the pregnant person's blood. This cfDNA includes DNA fragments from both the pregnant person and the developing baby. By analyzing these DNA fragments, the test can estimate the risk of certain chromosomal abnormalities.
Example:
Imagine a pregnant person undergoes cell-free DNA screening and the results indicate a high risk for Down syndrome. This doesn't definitively mean the baby has Down syndrome. It means further testing, such as amniocentesis, is recommended to confirm the diagnosis.
