Getting an unexpected NIPT result can feel unsettling, especially if you're not sure what it really means. But before you panic, it’s important to remember that NIPT is a screening test, not a diagnostic one — a positive or negative NIPT test result doesn’t guarantee that your baby does or doesn’t have a condition.
Several factors can increase a NIPT’s false positive rate, including confined placental mosaicism, vanishing twin syndrome, or maternal DNA influences. This is why it’s crucial to consider all possible explanations before making any major decisions.
In this article, we’ll break down how common NIPT false positive reports are, the key factors that can cause inaccurate results, and the next steps to take.
What is an NIPT?
A noninvasive prenatal test (NIPT) analyzes fragments of your baby’s DNA, called cell-free fetal DNA, that circulate in your bloodstream during pregnancy. This test is used to assess the risk of certain chromosomal conditions in the baby.
Typically, each child inherits 23 pairs of chromosomes from their parents. NIPT looks for any that may be missing or duplicated, which could signal a condition that affects development.
Your baby’s DNA becomes more detectable after the first trimester, which is why the test is usually performed after 10 weeks of pregnancy. If you get the test earlier, the results could be less reliable due to low fetal fraction (that is, a small amount of the baby’s DNA in your blood).
The chromosomal conditions that NIPT screens for usually include:
Trisomy 21 (Down syndrome)
Trisomy 18 (Edwards syndrome)
Trisomy 13 (Patau syndrome)
Turner syndrome (Monosomy X)
Klinefelter syndrome (XXY condition)
Your NIPT results will be reported as positive or negative. A positive result means there’s a higher risk that the baby has the specific condition, while a negative result indicates a lower chance.
Bonus — Want to compare NIPT with other prenatal tests? Check out the articles below:
Can a NIPT test be wrong?
NIPT is a screening test, which means it only estimates the likelihood that your baby has a certain chromosomal condition. It doesn’t provide a diagnosis.
While NIPT is highly accurate for conditions like Down Syndrome (up to 90% accuracy), it’s less precise for rarer chromosomal abnormalities (accuracy between 2 and 30%).
When a NIPT result is inaccurate, it can either be classified as a false positive or a false negative:
Type of error | What it means |
|---|---|
False positive NIPT | The test suggests a higher chance that your baby has a chromosomal condition when they actually don’t |
False negative NIPT | The test suggests a low chance that your baby has chromosomal abnormalities when they actually do |
Since NIPT results aren’t 100% accurate, some couples worry about getting a false positive or false negative and decide to skip the test altogether. This is understandable since no one wants unnecessary stress or uncertainty during pregnancy.
How often are NIPT tests wrong?
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While NIPT is generally highly accurate, how often it gives a false positive or false negative depends on the condition being tested.
For example, NIPT is the most reliable method for detecting Down syndrome, with false positives happening in only about 0.1% to 0.2% of cases.
However, the same can’t be said for Trisomy 18 and 13, as false positives and negatives are more common with these conditions. This means that if you receive a high-risk result for either of these, there’s a greater chance it might not be correct compared to a high-risk result for Trisomy 21.
To understand why this happens, it helps to know about two key terms: sensitivity and specificity. Here’s a breakdown of both:
Term | Meaning | Effect |
|---|---|---|
Sensitivity | It refers to how well the test can detect a condition when it’s actually there. A highly sensitive test rarely misses affected pregnancies. | If a NIPT has 99.9% sensitivity for Down syndrome, that means if 1,000 babies have Down syndrome, the test will correctly identify 999 of them but might miss one (false negative). |
Specificity | It refers to how well a test rules out a condition when it’s not there. A highly specific test rarely misidentifies healthy pregnancies as affected. | If the test has 99.5% specificity, that means if 1,000 babies don’t have Down syndrome, it will correctly say 995 of them are low-risk, but it might still wrongly label five pregnancies as high-risk (false positive). |
A study found that NIPT tends to have higher sensitivity than specificity for some trisomies, meaning it’s very good at detecting affected pregnancies but has a slightly higher chance of flagging healthy pregnancies as high-risk.
Since specificity plays a key role in false positives, this explains why some people receive high-risk results even when their baby is healthy. However, sensitivity and specificity can vary by provider, so it’s important to check the specific accuracy rates of your test.
Why do false positive NIPT results occur?
Several factors can cause your test to come back as high risk even when everything is fine, including:
Confined placental mosaicism
Maternal DNA influence
Vanishing twin syndrome
Lab processing errors
We’ll explain each of these factors in the sections below.
1. Confined placental mosaicism
NIPT analyzes fetal DNA fragments in your bloodstream, but most of that DNA actually comes from the placenta. Sometimes, the placenta may have chromosomal abnormalities that don’t affect the baby, called confined placental mosaicism (CPM). Here, the placenta contains extra or missing genetic material, but the baby’s actual DNA is normal.
Because NIPT can detect placental DNA, this discrepancy can lead to a false positive result and make it seem like your baby has a condition (when, in reality, it doesn’t).
2. Maternal DNA influences
When you get an NIPT, the blood sample contains DNA from both you and your baby. Although the test focuses on your baby’s DNA, sometimes certain factors in the mother’s DNA can affect the results and lead to a false positive report.
The most common factors include:
Maternal fibroids: Fibroids are non-cancerous growths in the uterus. While they don’t directly affect pregnancy, some research suggests they may increase the chances of a false positive NIPT result.
Maternal malignancies: In rare cases, an undiagnosed cancer in the mother can interfere with NIPT.
3. Vanishing twin syndrome
Sometimes, a pregnancy starts with twins, but one embryo stops developing early on and is naturally absorbed by the second twin, the placenta, or the mother’s body. This is called vanishing twin syndrome.
Many parents don’t even realize this happened because it can occur before an ultrasound can detect the second baby.
Since NIPT analyzes fetal DNA in the mother’s blood, the test may still pick up DNA fragments from the vanished twin. If that twin had a chromosomal abnormality, it could lead to a false positive result, even if the surviving baby is entirely healthy.
4. Lab processing errors
Although NIPT providers generally follow strict protocols to ensure accuracy, lab processing errors can still happen. Mistakes like mislabeling samples, improper handling, or errors during data analysis may lead to inconclusive results.
Sometimes, samples may even be lost or contaminated, requiring a repeat test. While these errors are rare, they can contribute to false positive or false negative NIPT results.
What to do after receiving unexpected NIPT results
Receiving positive or negative NIPT results can be an emotional experience, especially if you’re uncertain about their accuracy. Here are some options you can consider if this happens:
1. Genetic counseling
Source: MART PRODUCTION
Genetic counselors specialize in helping expectant parents understand complex genetic test results, including NIPT. If you’re uncertain about your report, a counselor can walk you through your results, discuss additional testing options, and offer valuable insights based on your unique situation.
Their role isn’t to tell you what to do — it’s to provide clear, science-backed information and guidance that helps you make an informed choice.
2. Amniocentesis
Unlike NIPT, amniocentesis is a diagnostic test — it provides a definitive answer about whether a baby has a genetic condition. Many people choose to undergo amniocentesis after receiving a high-risk NIPT result to confirm a diagnosis. This test is usually done during the second trimester of pregnancy.
Since this test involves extracting amniotic fluid from the womb, it comes with risks, including a 0.1% risk of miscarriage (1 in 900 pregnancies). Before deciding on amniocentesis, it’s essential to discuss the risks and benefits thoroughly with your healthcare provider.
3. Chorionic villus sampling (CVS)
Chorionic villus sampling (CVS) is another prenatal diagnostic test that can confirm chromosomal conditions. CVS involves taking a small sample of placental tissue. Since the placenta shares genetic material with the baby, this test can provide an early diagnosis.
One key advantage of CVS is that it can be performed earlier in pregnancy than amniocentesis, usually between 10 and 13 weeks. Still, because it’s invasive, there is a risk of pregnancy complications, so speak with your healthcare provider to determine if it’s the right choice for you.
Navigating your NIPT results and understanding additional options
Receiving a high-risk NIPT result can feel overwhelming, but it’s important to stay calm and gather the right information. Since NIPT is not a diagnostic test, false positives can occur, and follow-up testing is often needed to confirm a diagnosis.
In addition to NIPT, carrier screening is another valuable tool for couples planning a pregnancy. This test identifies whether you or your partner are carriers of genetic conditions that could be passed on to your child, such as cystic fibrosis, hemophilia, or muscular dystrophy.
For the most thorough insight, many experts suggest expanded carrier screening, which tests for hundreds of conditions instead of just a handful. Nucleus offers whole-genome sequencing-based carrier screening, testing for 900+ inherited conditions with a focus on accuracy and accessibility.
With a clear understanding of your genetic risks, you can make informed reproductive choices that best suit your family’s future.
Nucleus: Helping you take control of your reproductive health
Nucleus offers clinical-grade carrier screening with whole-genome sequencing (WGS). Unlike most traditional carrier screening tests that analyze less than 1% of your genome, WGS examines nearly 100%, making it far more capable of detecting rare genetic variants linked to inherited conditions.
One of the biggest advantages of Nucleus is its extensive carrier screening panel, which tests for 900+ genetic conditions, including:
Cancers like colorectal, breast, and prostate
Age-related macular degeneration
Celiac disease
Heart diseases like coronary artery disease
Chronic pain
Your results will also be presented in easy-to-understand reports, ensuring you can clearly interpret your genetic risks.
For couples planning a family, Nucleus’s partner syncing feature is a major benefit. If both you and your partner take the test, Nucleus will analyze your results together and give you a combined genetic risk assessment. This makes it easier to determine whether you are both carriers for the same condition and what that might mean for your future children.
After testing, Nucleus offers strong support services. Nucleus AI provides personalized conception recommendations, guiding you based on your genetic profile.
If you need further assistance, you can also take advantage of Nucleus’ partnership with SteadyMD, which has board-certified genetic counselors who can offer valuable insights and help you understand your next steps.
How to get started with Nucleus
The Nucleus carrier screening test is non-invasive and requires you to swab your cheeks to collect the sample. For $499, you get the full package, which includes the WGS test, a cheek swab kit with easy-to-follow instructions, prepaid shipping, and genetic reports with clear insights.
Also, if you decide to do the test with your partner and order two kits, you'll receive a $200 discount and only have to pay $798 for partner testing.
Here’s how you can get started:
Provide your personal details
Order your test kit
Once your sample reaches the lab, it takes six to eight weeks for your results to be released. You’ll receive your detailed genetic report, empowering you to make informed family-planning decisions.
If you’re ready to take a proactive step toward understanding your genetic health, you can start your journey today by ordering your Nucleus test and receiving unparalleled insights.
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