- NIPT is a Non-Invasive Prenatal Test (NIPT) performed on maternal blood to screen pregnancies for the most common fetal chromosome anomalies: trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome).
- NIPT is performed on a maternal blood sample which contains DNA from the fetus.
- During pregnancy, there are cell-free DNA fragments (cfDNA) from both the mother and fetus in maternal circulation. It is possible to analyze cell-free DNA to detect fetal trisomies such as Down syndrome (trisomy 21).
When you’re pregnant, your blood naturally contains small amounts of fragments of your baby’s DNA.
20 ml blood (2 tubes) from the mother can be taken into specific blood tubes. The maternal blood can be taken from week 10 of the pregnancy.
During pregnancy, there are fetal cells and cell-free DNA fragments (CFDNA) from the fetus in the maternal circulation. DNA isolated from maternal blood therefore not only contains maternal DNA but also a small amount of fetal DNA: the fetal fraction of cell-free DNA in maternal blood from week 10 on is about 10-15% of all cell-free DNA.
It is possible to analyze this cell-free DNA to detect fetal trisomies such as Down syndrome (trisomy 21).
Collecting your blood sample for NIPT poses no threat to your baby.
WHAT DOES NIPT SCREEN FOR?
- Down syndrome (Trisomy 21), which is caused by an extra copy of chromosome 21. Mild/moderate mental retardation and the risk of some birth defects (affects 1 in 1,000 live births).
- Edwards’s syndrome (Trisomy 18), which is caused by an extra copy of chromosome 18. Severe mental retardation and the risk of multiple birth defects (affects 1 in 3,000-6,000 live births).
- Patau syndrome (Trisomy 13), which is caused by an extra copy of chromosome 13. Severe mental retardation and the risk of multiple birth defects (affects 1 in every 5,000 live births).
The test can also detect abnormalities of the sex chromosomes:
- Turner syndrome (Monosomy X), which is caused by a missing X chromosome in females
- Klinefelter syndrome (XXY), which is caused by an extra X chromosome in males
- Jacobs syndrome (XYY), which is caused by an extra Y chromosome in males
- Triple X syndrome (XXX), which is caused by an extra X chromosome in females
WHAT IS DIFFERENT ABOUT NIPT?
In recent decades, screening for chromosome abnormalities during pregnancy has been called ‘first-trimester screening’ (FTS). FTS and NIPT are very different types of tests, both in what they test and the accuracy of their results. However, together they offer you very important information about your developing baby.
First-trimester screening combines the results of biochemical blood tests with the structural findings measured under ultrasound to predict the chance that your baby has a chromosomal or other structural abnormality.
NIPT is a genetic test that analyses your baby’s DNA fragments that are circulating in your bloodstream to detect the most common chromosomal abnormalities. By directly analyzing your baby’s DNA, NIPT results have been shown to be more accurate and have fewer false positives (i.e. abnormal results that are incorrect) than FTS in identifying Down syndrome cases.
HOW ACCURATE IS NIPT?
NIPT is more accurate than traditional first-trimester screening and much less likely to give a false positive result. That means there will be much less chance your doctor would recommend follow-up testing, such as amniocentesis.