NIPT (Noninvasive prenatal testing)

What is NIPT?

NIPT (noninvasive prenatal testing) is a blood test used to screen for Down syndrome and a few other chromosomal conditions. (It doesn't test for all chromosomal disorders.) NIPT is also known as cell-free DNA screening (cfDNA). Or you may have heard it called MaterniT21, a brand name.

The test is available to all pregnant women, and some healthcare providers offer it to all of their patients. The cost varies widely, but most insurance plans cover at least a portion of the fee.

Some labs will use the NIPT to screen for additional conditions. Work with your provider or a genetic counselor to decide which conditions you want your baby to be screened for. While NIPT screening for some conditions is very accurate – and very helpful for many families – some of these added tests have high inaccuracy rates.

Benefits of NIPT

NIPT is a simple procedure that provides a lot of useful information. There are some good reasons why it's such a popular test:

• It's not invasive. A simple blood draw taken at a regular prenatal checkup is all you need. There's no need to schedule and take the time for an invasive procedure, like amniocentesis or CVS.
• It's perfectly safe for you and your baby and carries none of the potential risks of some other testing. (Amniocentesis and CVS carry a small risk of miscarriage, for example.)
• While you'll need follow-up diagnostic testing to confirm results, negative results provide a high degree of accuracy – and reassurance – for a number of conditions.
• It's available very early in pregnancy, at 9 to 10 weeks pregnant or later.
• Results are provided fairly quickly (within a couple of weeks, often sooner).
• If you want to know, the test can tell you if you're having a girl or a boy.

Is the NIPT test conclusive?

No, NIPT is a screening test, not a diagnostic test. That means the results don't indicate for sure whether your baby has a chromosomal condition. So, a "normal" NIPT result doesn't guarantee a healthy baby, and an "abnormal" result doesn't mean your baby definitely has a certain condition.

That said, when testing for the major conditions (see below), the NIPT test is very accurate – especially if you get a negative result.

For example, when testing for Trisomy 21 (Down Syndrome), the negative result accuracy of the test is 99.5 percent. If you get a negative result, there's less than a 1 percent chance that it's incorrect. For Trisomy 18, the negative result accuracy is 97.7 percent, and for Trisomy 13 it's 96.1 percent. If you get a negative result for these conditions, there's a high likelihood that the test is correct and you can feel fairly confident that you don't need any further testing.

If you get a positive result, however, the accuracy is less reliable. That means you could get a "false positive" result that would be concerning and might lead you to have additional testing. For Trisomy 21, the chance of a positive result being correct ranges from 33 percent to 83 percent. (The accuracy range is a bit lower for Trisomy 18 and Trisomy 13.) Your more likely to get a false positive if you're at low risk of having a baby with a chromosomal condition. (Risk depends on factors such as your age and whether you have another child with the condition.)

Occasionally (from 1 to 5 percent of the time) a test doesn't yield a result, perhaps because of insufficient fetal DNA in the sample taken. Your provider can review your options with you if this happens.

The NIPT may be less accurate for you if you:

• Are obese (have a BMI of 30 or higher)
• Are pregnant with multiples
• Are pregnant as a result of IVF
• Are taking certain blood thinners

Currently CVS and amniocentesis are the only two tests used to diagnose Down syndrome and other chromosomal conditions prenatally, so if NIPT indicates a possible problem, experts recommend having CVS or amniocentesis for a definitive diagnosis.

How does the NIPT test work?

You have a simple blood draw, and your blood sample is sent to a lab for analysis. The test counts fragments of DNA from your placenta that's circulating in your blood, so it contains cells from both you and your pregnancy. These fragments are free-floating rather than within cells, so they're called cell-free DNA.

By examining the chromosomes (the part of cells that contain genes), doctors can tell if your baby is more likely to have certain disorders. There are normally two copies of a chromosome. If one of the pairs has an extra chromosome, it's called a trisomy. Down syndrome is also called trisomy 21 because there's an extra copy of chromosome 21, for example.

With all this examining of chromosomes, NIPT can also tell you what sex your baby is. Make it clear to your provider whether or not you want this information revealed to you when you get your results.

What does NIPT screen for?

The major conditions NIPT screens for are:

• Trisomy 21 (Down syndrome)
• Trisomy 18 (Edwards syndrome)
• Trisomy 13 (Patau syndrome)
• Common sex chromosome conditions, such as Klinefelter syndrome and Turner syndrome

Some labs may screen for a few other conditions as well, if you choose.

In many cases, the results of these tests are much less accurate than those for the conditions listed above – so if you're concerned about these, you may prefer to have definitive testing (an amnio or CVS).

Added tests may include:

• Trisomy 16
• Trisomy 22
• Triploidy
• Sex chromosome aneuploidy
• Certain disorders caused by a small chromosomal deletion (microdeletion syndrome)
• Certain single-gene disorders

What does NIPT not screen for?

Conditions not screened for include:

• Neural tube defects
• Heart defects
• Abdominal wall defects
• Many other chromosomal and genetic disorders

NIPT only screens for some chromosomal conditions. CVS and amnio, on the other hand, can diagnose almost all chromosomal abnormalities. They can also be used to check for any of several hundred genetic disorders, such as cystic fibrosis, if you ask for these extra tests.

If you're feeling like there are a lot of testing options for you during pregnancy, you're right. Throughout pregnancy, you'll be offered tests to check on you and your growing baby. Our prenatal testing article provides a good rundown of those tests.

Learn more:

• Your pregnancy week by week
• When will my pregnancy start to show?
• How to have a healthy pregnancy and baby