Did you know that pieces of your baby’s DNA circulate in your bloodstream? Noninvasive prenatal testing (NIPT) involves a simple blood screening that uses that DNA (it’s called cell-free DNA, or cfDNA) to analyze baby’s risk for a number of genetic disorders, including Down syndrome.
But the tests themselves can produce false positives, especially for rarer conditions, which can cause unnecessary anxiety. Here’s what you need to know to make sure these screenings are right for you.
What is noninvasive prenatal testing (NIPT)?
NIPT is a prenatal screening that looks at DNA from your baby's placenta in a sample of your blood to identify whether you’re at increased risk of giving birth to a child with a genetic disorder. A screening like NIPT cannot, however, determine for sure whether your baby actually has a chromosomal disorder, only the likelihood of having that condition.
The results of an NIPT screening can help you and your doctor decide on next steps, including whether to have a diagnostic test like chorionic villus sampling (CVS) or amniocentesis ("amnio"). These genetic tests analyze a baby's own genetic material, collected from the amniotic fluid or placenta, to tell with 100 percent certainty whether a baby has a chromosome abnormality. However, CVS and amnio are invasive, which means they slightly increase the chance of miscarriage.
How is NIPT done?
Because an NIPT involves only a quick blood draw with a needle and syringe, it's safe for you and your baby. All you’ll need to do is offer up your arm at the doctor’s office or a lab. Your sample is then sent to a lab, where a technician will look at the DNA in your blood for signs of abnormalities.
Once the results of your NIPT are back, your doctor will likely pair them with the results of your first-trimester ultrasound or nuchal translucency screening to determine whether further testing is needed. Depending on the results, your doctor may recommend following up with amniocentesis or CVS to confirm the result and check for other problems NIPTs can’t detect.
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What does NIPT screen for?
All NIPTs screen for the most common chromosomal disorders:
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Patau syndrome)
It can also reveal if your baby is Rh positive or negative and help your practitioner determine if you'll need a RhoGAM shot during pregnancy.
Since the test looks at a sample of your blood, some researchers think it may eventually also be used as a screening tool for moms, too. Further research is needed before practitioners begin using the tests for this purpose.
Does NIPT show baby's gender?
NIPT also detects your baby’s sex, so be sure to let your doctor know if you want to be surprised on delivery day!
What are the different kinds of NIPTs?
Multiple companies currently offer noninvasive prenatal testing, including Genesis Serenity, Harmony, Natera and MaterniT21.
Each one offers slightly different panels screening for various genetic disorders. Some screen for abnormalities including triploidy and microdeletion. And several brands' tests distinguish between maternal and fetal cfDNA, while others do not (which means they’re less accurate).
The Food & Drug Administration (FDA) does not review these tests, and the agency recently warned patients and health care providers that brands may make unfounded claims about the tests' performance. Discuss with your practitioner which type of test he or she uses as well as its risks and benefits.
When is NIPT done in pregnancy?
NIPT can be performed any time after 9 weeks into your pregnancy — earlier than any other prenatal screening or diagnostic test. In comparison, nuchal translucency screening is done between weeks 11 and 13; CVS is done at 10 to 13 weeks; the quad screen is completed between weeks 14 and 22; and amniocentesis is usually performed between weeks 16 and 18, though it's sometimes done as early as week 13 or 14 and as late as week 23 or 24.
How accurate is NIPT?
Research suggests that NIPTs have anywhere from 97 to 99 percent accuracy when it comes to predicting the risk of Down syndrome, Edwards syndrome or Patau syndrome. For these conditions, they create fewer false alarms than standard first-trimester blood screenings (like first-trimester bloodwork or quad screening) that measure hormones and special proteins in Mom's blood.
But these tests are much less accurate when it comes to predicting rarer genetic conditions such as DiGeorge syndrome, 1p36 deletion, Cri-du-chat syndrome, Wolf-Hirschhorn syndrome, Turner syndrome and Prader-Willi syndrome. For example, a research review found that cfDNA tests for Turner syndrome produced false postives 74 percent of the time.
That’s why if you do receive a positive result from NIPT, you should talk to your practitioner about getting a more definitive diagnostic test done, such as CVS or an amnio, before making any decisions.
Should you get NIPT?
In the past, NIPTs were only recommended for women at high risk for carrying a baby with a chromosomal abnormality — like moms-to-be who are 35 or older, previously had a child with a genetic disorder or have a family history of these conditions — or if there was a concern about the result of another prenatal test.
ACOG now recommends that doctors discuss all screening options with all pregnant women — regardless of age or risk — to figure out which one, if any, is most appropriate. The decision is a personal one, and this counseling phase is important. Just because a test was right for a friend doesn’t mean it’s right for you.
Be sure to ask your health care provider to spend some time going over all your choices. Considering how quickly the science is evolving, the guidelines about which screenings are best for you may change.
Before you get tested, double-check with your insurance company to find out if NIPT is fully covered — and if not, what it will cost you.
Also, while getting this test done is far from scary (unless you really hate needles), you may be nervous about seeing the results. If this is the case for you, consider talking to your doctor or to a genetics counselor about what positive test results could mean for you and your baby.
For many parents, knowing as much as possible as soon as possible is better. Finding out about potential conditions early on allows you to prepare for a special needs baby and make plans to deliver at a facility that can better address your and your baby’s health needs right away.
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