What is Non-Invasive Genetic Testing?
When women find out they're pregnant it's normal to feel overwhelmed by the volume of information available and number of decisions that you're being asked to make about everything from testing options to whether you're going to use a doula.
Having 1 or more ultrasounds during pregnancy is a way for moms and families to feel more reassured about the health of their baby, and now there are more options to screen for possible genetic conditions.
One of the first questions many pregnant moms have is what kinds of tests are available and what should they have for possible genetic conditions in their pregnancy.
A New Highly Accurate Option to Screen for Genetic Conditions
Now, using a simple blood test from a mom as early as 10 weeks in her pregnancy, we can detect the most common genetic conditions with > 99% accuracy and very low, < 0.1% false positive rates. For a quick overview of the latest option in Prenatal Genetic testing, you can click on this video, which explains the Harmony Prenatal Test.
No Risk to Mom or Baby
Previously, the best we could offer to women was a series of ultrasounds and several blood tests in both the first and second trimesters that had low accuracy rates that ranged from 60-80% up to 85-95%.
While a 95% accuracy rate seems good, it still means that the false positive rates are 5%, which means that thousands of moms every year get worrisome results and are asked to repeat blood tests and then have an invasive confirmatory test such as CVS or Amnio.
The false positive results are an important limitation of the tests outlined below in this post. These false positive results caused many women to have unnecessary invasive testing, some miscarriages and weeks of worry.
With Non-Invasive testing using the Harmony Prenatal Test, moms have the opportunity to have 1st trimester testing that is > 99% accurate with less than 0.1% false positive rates. This has reduced the number of unnecessary Amniocentesis, CVS and eliminated weeks of worry for moms, their partners and families.
Why do we offer genetic testing in pregnancy? Simply, because we now have the ability to detect conditions and provide moms and their families more information. Let's back up a bit and talk about genetics to better understand what we're testing for.
We all have pairs of chromosomes in each of our cells, in fact, there are 23 pairs of chromosomes that carry our unique DNA and the genetic information that makes each of us who we are–from influencing and determining our hair and eye color to how tall we are. The most common genetic conditions are known as Trisomies and occur when an extra or 3rd chromosome is present. The most common genetic conditions are very rare:
- Trisomy 21 also known as Down Syndrome, affects approximately 1 out of every 750 newborns
- Trisomy 18 also known as Edwards Syndrome, affects approximately 1 out of every 5,000 newborns
- Trisomy 13 also known as Patau Syndrome, affects approximately 1 out of every 16,000 newborns
Now, with the Harmony Prenatal Test, we can test a mom's blood when she's at least 10 weeks pregnant and provide very high accuracy with very low false positive rates.
Safe, Simple & Accurate
- The Harmony Prenatal Test uses a highly efficient, directed analysis that tests for the fetal cell-free DNA circulating in the mom's blood.
- The very high detection rates and very low false positive rates translates into fewer unnecessary invasive tests with Amnio and CVS.
- Detects > 99% of Trisomy 21, Down Syndrome with < 0.1% false positive rate
- Detects > 99% of Trisomy 18, Edwards Syndrome with < 0.1% false positive rate
- Detects 8 out of 10 Trisomy 13, Patau Syndrome with < 0.1% false positive rate
Other Testing Options
As a comparison, I've included the other testing options here with their accuracy rates. The False positive rates for all of these are in the range of 5-10%.
NT (nuchal translucency)—This ultrasound measures the baby’s neck (nuchal) fold thickness at 11 to 14 weeks to screen for Down Syndrome. This test by itself has a 60 to 80% accuracy.
Combined screening—Uses a blood test from the pregnant mom that measures pregnancy proteins and is done at 9 to 14 weeks. The results are then combined with the NT (nuchal translucency ultrasound) measurements to assess risk of Down Syndrome. The benefit of this test is that it's not invasive and therefore, there is no risk of miscarriage. These combined tests will detect about 85% of affected pregnancies.
Combined Integrated Screening – Also known as Stepwise Sequential Screening. This helps determine the risk of Down Syndrome by using the results from the Combined Screening done at 9 to 14 weeks combined with the Quad Marker test done at 15 to 20 weeks in the 2nd trimester.
This test screens for Down Syndrome, Trisomy 18 and spinal cord or neural tube defects (NTD). The accuracy is approximately 90 to 95% when all these tests are done together. Often families receive one set of results from the first test that can be worrisome and then have to wait for the second Quad Marker test results before finding out if the baby is okay. The benefit of this test is that it's not invasive and therefore, there is no risk of miscarriage. However, waiting for the results can be very difficult emotionally.
Quad Marker Test - Also known as the AFP (Alpha-Feto-Protein) test, this is performed at 15 to 20 weeks. It is most accurate between 16 to 18 weeks. This test helps find babies with Down Syndrome, Trisomy 18 or a spinal cord or neural tube defect (NTD). About 70% of babies with these genetic disorders and about 90% with NTDs are found. If the test is positive, further testing with ultrasound and amniocentesis is advised. The benefit of this test is that it's not invasive and therefore, there is no risk of miscarriage. This test is done in the 2nd trimester, which means that moms must wait for results for several weeks.
More Accurate and Simpler
Having a new option, using a simple blood test as early as 10 weeks of pregnancy, with Non-Invasive Prenatal Testing, NIPT, the Harmony Test, means that moms can have more peace of mind.
With > 99% accuracy and < 0.1% False positive test results, this is the test that I recommend for pregnant moms.
Disclosure: After reviewing the research on Non-Invasive Prenatal Genetic Testing, I began working with Ariosa Diagnostics to help educate and inform pregnant women about their range of prenatal testing options.
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