What Do Noninvasive Prenatal Tests (NIPTs) False Positives Mean?

In 2022, The New York Times published a groundbreaking analysis of noninvasive prenatal tests (NIPTs), finding that they produce inaccurate results up to 85% of the time. If you are pregnant or someone who hopes to become pregnant in the future, this news may have caught you off guard and made you feel concerned.

That's totally understandable—these are worrisome stats, and you may be unsure about what this means for you. You may be wondering if you should get any NIPT screenings at all. If you've received concerning results from one of these tests, you may feel unsure what the results mean and what additional steps you should take.

The topic of NIPTs can be confusing, and the information can feel very technical and difficult to understand. Read on for a breakdown of NIPTs, when NIPT false positives are more likely, and how to make the best decision for you.

What Are NIPT Tests?

NIPT tests are screening tests used to determine if your baby might be born with a genetic abnormality. According to the National Library of Medicine, these tests are noninvasive and analyze a blood sample for DNA from your fetus.

During pregnancy, small fragments of your baby's placenta DNA end up in your bloodstream and can be detected and analyzed. These free-floating DNA fragments are called cell-free DNA (cfDNA) and may contain information about your baby's genetic makeup.

NIPT tests look for the following chromosomal conditions:

• Down syndrome
• Trisomy 18
• Trisomy 13
• Missing copies of X and Y chromosomes

It's important to understand that NIPT tests are screening tests. In other words, they are not definitive results about what genetic condition your baby might have.

They can tell you whether your baby has an increased or decreased risk of having a genetic abnormality, not whether they actually do. Since these tests evaluate fetal and maternal DNA, these tests can also detect a gestational parent's genetic condition.

You will need a diagnostic test, such as amniocentesis or chorionic villus sampling (CVS) to confirm or deny the results from a NIPT test. These diagnostic tests can be informative but slightly increase your risk of miscarriage.

How Common Are False Positives?

According to The New York Times investigation, NIPT tests are thought to be highly accurate in assessing your baby's risk for Down syndrome, one of the first uses of these tests. However, when it comes to rarer genetic abnormalities, there are more possibilities for NIPT false positives.

Results varied from one test to another, but The Times found that these tests consistently gave inaccurate results on average 85% of the time. In addition, these tests have not been evaluated by the U.S. Food and Drug Administration (FDA).

The FDA says they are aware of cases where people have terminated pregnancies for medical reasons based on results of NIPT false positives, where the fetuses are later found to be healthy. This is why the American College of Obstetricians and Gynecologists (ACOG) guidelines reiterate that cfDNA has the potential for false positive and false negative results and is not the equivalent of diagnostic testing.

In their independent investigation, The New York Times looked at studies and interviewed researchers about five different prenatal tests that screened for rare genetic conditions. The screenings they analyzed included tests that looked for the following:

• DiGeorge syndrome
• 1p36 deletion
• Cri-du-chat syndrome
• Wolf-Hirschhorn syndrome
• Prader-Willi syndrome
• Angelman syndrome

These are extremely rare conditions—for example, according to the Genetic and Rare Diseases Information Center, Wolf-Hirschhorn syndrome affects less than 50,000 people in the U.S.—but can cause lifelong physical and intellectual disabilities.

According to the FDA, more common conditions, like Down syndrome, have higher positive predictive values—90%. That means that 9 out of 10 suspected Down syndrome screenings are confirmed with diagnostic tests. However, the rarer conditions have much lower positive predictive values, ranging from 2-30%.

Should You Get A NIPT Test?

ACOG recommends that all pregnant individuals be offered NIPT screenings whether or not they have a known risk factor, including advanced age. This doesn't mean that a health care provider will recommend that you get screened for every genetic condition, though.

For example, since the risk of Down syndrome increases with maternal age, a health care provider might recommend screening if you're over 35. But they may not recommend one of the rarer genetic screenings that The Times investigated. The decision about which genetic conditions to screen for should be made in collaboration with your health care provider.

The pros of NIPT tests

According to researchers, some of the benefits of NIPT testing include:

• It can be performed in the first trimester of pregnancy.
• It is non-invasive and holds no risk of miscarriage.
• It is more accurate in detecting Down syndrome than other screening tests.

For some people, NIPT tests can provide reassurance early in pregnancy. In addition, it can help some people avoid more invasive tests or help them plan for further tests only if indicated.

The cons of NIPT tests

For others, all of the waiting and the anxiety that comes with testing may not be worth it. Some of the downsides of NIPT tests include:

• Stress and anxiety if screening tests are positive
• High rate of NIPT false positives for rarer conditions
• You'll have to wait until the second trimester for follow-up diagnostic tests

Blood tests for genetic abnormalities are usually conducted as early as 10 weeks of pregnancy. But follow-up diagnostic tests, like amniocentesis and CVS, are generally done between the 15th and 20th week of pregnancy.

So, if your NIPT test tells you that your baby might have a genetic condition, there will be a waiting period until you can get a diagnostic test to tell you whether your baby does, in fact, have one of these conditions.

The waiting period can be grueling. However, people with known risk factors, such as genetic conditions in their family, may decide that these tests are vital.

Where To Go From Here

Seeing a scary headline about genetic tests and high NIPT false positives can be enough to increase your blood pressure; but knowledge is power.

Even though you may feel overwhelmed as you absorb this information, keep in mind that you have choices when it comes to your prenatal care. Learning that screening tests like NIPTs can sometimes be inaccurate is a great opportunity to have an open discussion with a health care provider about your options and which screening tests make sense for you and your pregnancy.

If you are dealing with some upsetting results from a NIPT screening and waiting for further confirmation, know that you aren't alone: Many parents have navigated these extremely stressful situations.

Again, speaking to a health care provider about what this means, how accurate these results are, and what your next steps should be, is essential. If you feel that your provider isn't listening to you or communicating clearly, you might consider switching providers or getting a second opinion.

Importantly, the mental health impact of screening, testing, and upsetting results should not be underestimated. If you are experiencing heightened stress or anxiety, please reach out to a health care provider or a mental health professional. You deserve to feel balanced and well.