NIPT (Prenatal cfDNA Screening)
Definition
A blood test performed during pregnancy. It examines fragments of fetal DNA circulating in the mother's bloodstream. Blood is drawn from a vein in the mother's arm; it is a quick procedure that causes no discomfort.
Purpose
Detects increased risk for three trisomy disorders:
| Condition | Description |
|---|---|
| Down syndrome (trisomy 21) | An extra chromosome 21, the most common chromosomal disorder |
| Edwards syndrome (trisomy 18) | An extra chromosome 18, rare, severe course |
| Patau syndrome (trisomy 13) | An extra chromosome 13, rare, severe course |
It can also determine fetal sex or the Rh blood group.
When it is done: It can be performed from the 10th week of pregnancy onward.
Results
- Negative, the likelihood of these disorders is low
- Positive, means increased risk, it cannot make a diagnosis
Risks and Limitations
This is the test in the glossary that requires the most careful explanation:
1. It cannot give a definitive diagnosis, a positive result must be confirmed with amniocentesis or CVS 2. There is a risk of false positives, a positive result does not mean the baby definitely has this disorder 3. It is less accurate in multiple pregnancies, in twin or higher-order pregnancies the screening is not reliable
The word non-invasive in the test's name means that the procedure carries no risk to the mother, not that the result is definitive. These two things are often confused.