What Is NIPT, or Noninvasive Prenatal Testing?
If you had a high-risk pregnancy or a child within the last 10 years, then you are probably familiar with NIPT, or noninvasive prenatal testing. A NIPT test is a blood test that screens a fetus for the most common chromosomal defects—including Down Syndrome, trisomy 13, and trisomy 18—as well as other sex chromosome abnormalities. MaterniT21, for example, is a common NIPT screen.
The NIPT test is quick and painless. It's a blood draw that can be performed in individuals who are at least nine weeks into their pregnancy. And while it's routinely offered to those with high-risk pregnancies, those who have had a child with a chromosomal disorder, and/or those who have had an ultrasound that showed a potential problem with their fetus, many obstetricians are now offering the test to all, regardless of age or pregnancy risk.
That said, NIPT comes with some risks. According to an investigation by the The New York Times, prenatal screening isn't always accurate, and it might return false positives.
Here's everything you need to know about NIPT, or noninvasive prenatal blood tests.
What Is NIPT?
NIPT is a prenatal test that looks at DNA from your baby's placenta to identify whether you're at increased risk of giving birth to a child with a genetic abnormality.
How Does NIPT Work?
During pregnancy, your blood contains both maternal DNA and cell-free fetal DNA, which is DNA from the placenta that has crossed into your bloodstream. NIPT measures the fragments of this circulating fetal DNA, and if the test detects abnormal amounts of certain DNA, then the screening would come back positive. For example, high amounts of chromosome 21, 13, or 18 suggest that the fetus may have an extra copy of one of those chromosomes in each cell in the body, rather than the usual two copies. Having an extra 21 chromosome can lead to Down Syndrome.
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What has doctors and researchers particularly excited about NIPT, however, is its accuracy compared to the serum tests previously offered. "One out of 20 individuals who had a serum screen for Down Syndrome would get a false positive, whereas 1 out of 1,000 getting NIPT are getting a false positive," says Blair Stevens, M.S., CGC, a genetic counselor at the University of Texas Health Science Center in Houston. However, the test is not fail-proof. False positives can and do occur.
What's more, NIPT is a screening tool, not a diagnostic tool. A positive test result signals that you will have to undergo a more invasive diagnostic test, such as an amniocentesis or chorionic villus sampling, which carry a small risk of miscarriage. Only those tests can definitively confirm or rule out a chromosomal disorder.
How Are NIPT Tests Performed?
If you choose to undergo NIPT, know the process is simple. It's nothing more than a blood draw. Once the blood has been collected, it is sent to a laboratory to be analyzed.
What Conditions Does NIPT Look For?
NIPT screens for a variety of chromosomal disorders, including:
- Down syndrome
- Edwards syndrome
- Patau syndrome
The test can also detect sex chromosomal disorders, like Jacob's syndrome, Klinefelter's syndrome, Trisomy X, and Turner's syndrome—though many use it to determine the baby's sex.
NIPT Pros and Cons
While NIPT tests can be beneficial, they have limitations. Individuals with low-risk pregnancies have far more frequent false positives than those who are considered high-risk. This can lead to unnecessary diagnostic procedures. In addition, a negative result does not guarantee that a fetus harbors no chromosomal abnormalities, and NIPT does not test for all chromosomal disorders. There are other conditions it cannot detect.
That said, since NIPT can also predict fetal sex some 10 weeks earlier than the standard ultrasound—and with a 99 percent accuracy—many soon-to-be parents are excited. But Stevens offers words of caution for parents seeking NIPT solely to discover the sex of the baby.
"We have had unfortunately several patients come to our office with abnormal results who were very confused and very regretful for having the test," says Stevens. They wanted a straightforward blood test to determine the baby's sex but ended up with devastating news they had not been prepared to receive. Stevens recommends that parents seek genetic counseling both before and after testing to make sure they understand what they are signing up for when they undergo prenatal testing.