These days there are many different screening options during pregnancy. One of them is the NIPT and you probably have a lot of questions. Let’s find out what non invasive prenatal testing (NIPT) is all about.
What is a non invasive prenatal test (NIPT)?
Prenatal screening is all about carrying out investigations on your baby to make sure everything is alright with your little one. It also means, in case you get a positive screening result, you have all the information you need and can have further investigations if necessary.
The non invasive prenatal test is a simple blood test that will look for genetic disorders in your baby. Noninvasive prenatal testing analyzes small DNA particles from the placenta, present in the pregnant woman’s blood.
Once the screening test has shown an increased risk of the baby having a chromosomal abnormality, further diagnostic testing will be offered by your healthcare providers to get a definitive answer on your baby’s genetic condition.
Screening tests vs diagnostic tests
In medicine, screening tests are investigations carried out in a group of individuals in order to find unrecognized conditions or risk markers that indicate certain conditions might be present. Prenatal screening means looking for specific conditions in all pregnant women who agree to these tests being carried out.
Screening tests will give you a risk parameter: they will show whether your baby has a risk of 1 in 200, 1 in 7000, or 1 in 47 of having that specific genetic disorder.
When this risk is high in the screening test, you will be offered diagnostic testing.
Diagnostic tests will give a definite answer on whether a baby has or does not have that specific condition.
When the noninvasive prenatal test is performed, you will be placed in a risk category. For example, if your NIPT results come back as 1 in 500, that means that the risk of your baby developing the tested condition is 1 in 500. Out of 500 babies with this same screening test result, one of them will have the studied condition.
In most countries, when the risk in a NIPT comes out higher than 1 in 200, diagnostic testing is then offered by the maternal-fetal medicine team, to find out for sure whether the baby has any chromosomal disorders.
What does NIPT screen for?
This noninvasive prenatal screening will help identify genetic conditions such as fetal chromosomal abnormalities.
The NIPT genetic testing will search for the following chromosomal abnormalities:
Trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome).
The NIPT also tests for chromosomal abnormalities affecting the sex chromosomes.
How does NIPT work?
A blood sample is taken from the mother, as small particles of placental DNA, called cell-free DNA, are mixed with her blood.
Once this different DNA has been identified the number of chromosomes that an individual has is easy to find. A human being normally has 46 chromosomes (23 pairs). If there is a chromosomal abnormality (aneuploidies) the NIPT will be able to identify it.
Can NIPT miss Down syndrome?
Down syndrome is also called trisomy 21. This means that there are three copies of chromosome 21 instead of the usual two.
If you get a negative NIPT screening test result for Down syndrome, it means trisomy 21 has been searched for and just two copies of chromosome 21 have been identified. It is highly unlikely that noninvasive prenatal testing would miss Down syndrome.
False positives are highly unlikely, however. Remember that this is a screening test that will place your baby in a risk category of developing that condition.
At the same time is very difficult to get a false negative test result. If you get a positive result you will then be offered a diagnostic test to confirm the suspicions the prenatal testing NIPT raised.
Does the NIPT show the sex of the fetus?
Yes, this type of genetic testing will identify the chromosomes in each individual’s cells. People with 46 chromosomes have 44 regular chromosomes plus two sex chromosomes that will define the baby’s sex.
The two sex chromosomes are XX for a female and XY for a male.
Other sex chromosome aneuploidies can also be detected by this noninvasive prenatal test – for example, Turner syndrome (when a person has just 45 chromosomes, and the single sex chromosome is X) or Klinefelter syndrome (when there are 47 chromosomes, and the sex chromosomes are XXY).
How accurate are NIPTs?
The non invasive prenatal test is highly accurate. It is a screening test, however, and that leaves some room for inaccuracy. Research shows that a false positive screening result is much more likely than a false negative result. The accuracy of noninvasive prenatal testing ranges from 90% to 99%.
When should the NIPT be done in pregnancy?
The NIPT can be done from 10 weeks of pregnancy onwards, as no detectable exchange of genetic material between mother and baby happens before then.
Noninvasive prenatal testing is usually done around week 13. This is to make sure that the baby’s DNA particles are present in the mother’s blood. When the NIPT is done at 13 weeks gestation, even those pregnancies that might have begun later than we think will still be more than 10 weeks.
Can NIPT be done at 14 weeks?
Yes, noninvasive prenatal testing can be done at any time during pregnancy, after 10 weeks.
Doing the test at 13 weeks of pregnancy has been chosen as the minimum number of weeks gestation, to ensure there’s enough cell-free DNA from the baby in the mother’s bloodstream.
Once this DNA exchange has taken place, cell-free DNA screening can be done at any time. You can have this test done a week before your due date if you’d like that. However, it’s also recommended to have the test done as early as possible so that, if a decision has to be made, it won’t be rushed.
Is it worth doing the NIPT?
Remember that all these tests are optional and you don’t need to have them done if you don’t want to.
The main reason prenatal testing is offered during the first half of pregnancy is to look for genetic abnormalities. If genetic tests confirm a chromosomal disorder, those families will then be offered diagnostic testing.
Once the positive result is confirmed, life expectancy and options for the baby with the particular condition will be discussed. Termination of pregnancy will be offered to those families.
I often have this discussion with my clients, as it’s a difficult decision to make.
If they are sure they would continue with the pregnancy, regardless of their baby’s condition, I tend to advise them to decline screening tests. If termination of pregnancy isn’t contemplated by the family, regardless of any genetic disorders or birth defects their baby might be born with, then the best option for this family should be to decline all screening testing.
Remember that a screening test places your baby into a risk category, estimating the chances of your baby developing that condition; it doesn’t give you a definite answer.
If you are going to carry on with the pregnancy no matter what, there’s no point in having a definite diagnostic test done. Diagnostic testing carries a risk of potential miscarriage, so you could be endangering your pregnancy just by testing.
At the same time, if a woman who doesn’t want to terminate her pregnancy gets a high chance of a genetic abnormality in the NIPT, throughout the whole pregnancy she will carry the extra worry of her baby possibly having a genetic condition.
Would the information you get in the NIPT change your course of action regarding the continuation of the pregnancy? If the answer is no, and you’d carry on with your pregnancy despite any conditions the baby might have, then my advice would be to decline NIPT screening tests and enjoy your pregnancy as much as possible and as worry-free as possible.
Is NIPT painful?
One of the advantages of NIPTs is how easy it is to collect a sample for testing. Testing for the NIPT just requires drawing blood from the mother’s forearm. So unless you’re needlephobic, it should just be a momentary sharp scratch. This is the main reason why this prenatal testing is called ‘non invasive’.
How much does the NIPT cost?
This is a very difficult answer as noninvasive prenatal testing is differently priced in different countries. It can range from less than 100 USD to over 1,000 USD
The vast majority of medical insurance covers this test for high-risk pregnancies. Some screening tests for low-risk pregnancies are also covered. Most labs will be able to find out for you what testing your insurance company provides. If you have to pay for this test out of pocket, many labs have financing options. Discuss your options with your healthcare providers, who will be able to assist you best with the costs of NIPT in your area.
Low chance result
A screening test will always give you a risk for the tested individual of having a low or high chance of having the tested condition.
There is no negative screening test result but a low chance result.
A low chance result means that yes, the chances are low for that baby to have that condition; however, there is still a chance the baby could have the searched condition and it not be identified.
Imagine your NIPT low chance result is 1 in 400. This means that out of 400 babies with this same screening test result, 1 of them will actually have the condition.
When the chance is 1 in 1000, the chances of your baby being the one with the tested condition are even lower.
Your baby’s chances of testing positive for any of the tested conditions are lower the higher the number against the 1. Therefore, 1 chance in 20,000 will always be lower than 1 chance in 37.
Further reading
Blood Test For Pregnancy | What You Need To Know
What Is Patau Syndrome? Trisomy 13 – All You Need To Know
What Is Edwards Syndrome Or Trisomy 18? All You Need To Know
