What is NIPT/ NIPS Test?

NIPS stands for non-invasive prenatal screening/testing. It involves a blood test taken from a pregnant woman, at least 10-11 weeks into the pregnancy.

NIPT can identify a pregnancy in which the baby is likely to have a chromosomal condition. These conditions do not usually run in the family and can occur in any pregnancy.

It is important to note that it is a screening test and will identify those with high risk. However it will not tell whether the baby has the condition or not.

What does NIPS screen for?

In the absence of prenatal diagnosis and therapeutic abortion, the prevalence of Down syndrome in developed countries is 1-2 per 1,000 births making it the most frequent identifiable cause of severe learning difficulty. NIPS has the capacity to detect more than 99% of Down’s syndrome(Trisomy 21) pregnancies.

It can also screen for other chromosomes. Human cells have 23 pairs of chromosomes, all of which can be evaluated in NIPS.

How accurate is NIPS?

NIPS is more accurate than combined first trimester screening and ultrasound test for detection of Down syndrome(>99%). However it is not as accurate for other trisomies.

How does NIPS work?

Mother’s blood contain small fragments of DNA in her blood which comes from her own cells as well as from the placenta(representative of the baby). This is a normal process.

NIPS analyses the proportion of DNA fragments that come from specific chromosomes. If a particular proportion is too high or too low, this indicates that there may be a chromosomal problem involving the placenta and hence potentially, the developing baby. (It is important to note that the baby’s DNA is not directly tested).

What does the results mean?

In the report we has something known as fetal fraction which checks whether there is sufficient DNA from the developing pregnancy to provide a reliable result. Then the result would indicate where there is high risk or low risk for any condition which is requested for.

If the result indicate low risk, it is very unlikely that the pregnancy would be affected by Down syndrome. (It is important to note that a low risk result does not rule out all genetic problems).

If the result indicate high risk, it does not mean that your baby has this condition. NIPS is a screening test. You would be offered invasive confirmatory testing after discussion.

Note:

If you are carrying twin pregnancy, the detection rate is slightly lower than that of single pregnancy.

If you had triplets/higher order pregnancy, this test is not validated for the same.

Limitations:

On rare occasion, it is not possible to issue an NIPT result. This is usually due to complex biology of pregnancy rather than a failure of test method. In some cases a second sample is recommended for repeat analysis.