NIPT (Non Invasive maternal cell free fetal DNA) is a prenatal screening which assesses fetal DNA in maternal blood with predicted detection rate for Trisomy 21 (Down Syndrome) of 99.6% with a 0.1% false positive and false negative rates.

If the results are negative, then very unlikely that the baby has a defect in chromosomes 21, 18 or 13. However, if it is reported as positive, then this will need to be further confirmed by Amniocentesis. The result of this test is expected in 2-3 weeks.

How is NIPT done?

NIPT is only a blood test and is absolutely safe for the mother and the baby. All you will need to do is to offer up your arm at the doctor’s office or a lab. A small amount of blood will be drawn and sent to the laboratory for testing. The result of this test is expected in 2-3 weeks.

What does NIPT screen for?

Most people have 23 pairs of chromosomes for a total of 46 — two copies of each set. The NIPT test is highly effective in determining if there is only one chromosome where there should be a pair, or if there is an extra chromosome, especially for the chromosomes that are responsible for Down syndrome, Edwards syndrome, Patau syndrome and certain sex chromosome trisomies. Panorama can also identify if there are three sets of each chromosome, which is known as triploidy.

• A trisomy occurs when there is an extra copy of any one chromosome — 3 copies instead of 2.
• A monosomy occurs when there is a missing copy of any one chromosome — 1 copy instead of 2.
• Triploidy occurs when there are 3 copies of all the chromosomes.

What is Fetal Fraction?

Maternal blood contains circulating cell-free DNA fragments originating from both the mother and the placenta. The proportion fetal DNA derived from the placenta with respect to total amount of cfDNA is known as the fetal fraction. 

Fetal fraction of DNA in the mother’s blood can vary greatly throughout gestation; it does tend to be lower earlier in the pregnancy. The lower the fetal fraction, less sensitive is the test. For e.g. if the fetal fraction is only 4% than the test performs at 60% sensitivity whereas if the fetal fraction is more than 8% it performs at greater than 99% sensitivity.

Should you get NIPT?

In the past, NIPTs were only recommended for women at high risk for carrying a baby with a chromosomal abnormality — like moms-to-be who are 35 or older, previously had a child with a genetic disorder or have a family history of these conditions — or if there was a concern about the result of another prenatal test.

ACOG now recommends that all screening options should be discussed with all pregnant women — regardless of age or risk — to figure out which one, if any, is the most appropriate. The decision is a personal one, and this counselling phase is important. Just because a test was right for a friend doesn’t mean it’s right for you.