Demystifying genetic testing for parents: Meet Maven's Genetic Counselor

Q&A with Maven Genetic Counselor Ushta Davar Canteenwalla, MS, LCGC

Maven: What does genetic testing mean during pregnancy and why does it matter?

Ushta Davar Canteenwalla: When we think about genetic testing that’s specific to pregnancy, what we’re referring to is typically any testing that is offered in pregnancy that gives us information about the baby’s genetic makeup, or the risk for the baby to have a genetic condition. There are many reasons why someone may consider a genetic test during pregnancy. People who are interested in learning more about the chance for their baby to have an increased risk of a genetic condition that could potentially impact physical or intellectual ability are typically the ones that end up choosing genetic testing most often.

Q: What kinds of genetic tests would be helpful for someone who wants to become a parent?

A: When someone asks me if there is a test they can do in the preconception phase before getting pregnant, genetic carrier screening is typically the test I recommend. Carrier screening is a blood test that’s done on the parents that can give meaningful information about potential increased risk for inherited genetic conditions. Knowing this information in advance can really be helpful in regards to creating more testing options and understanding overall risks.

Q: How do you know what type of genetic testing is right for you?

A: There’s no right or wrong way to approach genetic testing but it is important to figure out what options would be best for the types of information that matter most to you. Chatting with a Genetic Counselor can be informative in learning more about what tests may be optimal for you and helping make a decision. I recommend patients ask themselves what information they want to know, what they will do with that information or if that information will be meaningful to them and whether the timing is right for them to get the testing now. There are many factors to consider and the information provided can be stressful, overwhelming, and present a new set of challenges—so it can be a hard decision and shouldn’t be one that is taken lightly or alone necessarily.

Q: Let’s dive in to one specific type of genetic test for chromosome risks, which increases with age—a key driver of high-risk pregnancies. What is a type of test that can assess the risks for chromosome conditions?

A: You may have heard about the risk for chromosome changes as a woman gets older. And this is because, as women get older, so do our eggs, and the theory is that, as the eggs get older, the chromosomes just don’t separate the way we’d like them to. The key takeaway is that there’s always a risk for someone to have a chromosome abnormality, but this risk increases as a woman’s age increases.

There are a few tests that are offered in pregnancy to better understand risks for chromosome changes, which I’ll dive into specifics on here.  

• Maternal Serum Screening is a blood test that’s done on mom between 11 and 13 weeks into a pregnancy, and is often combined with an ultrasound around 12 weeks. It looks at the proteins made by the baby circulating in mom’s blood, and combines it with information like mom’s age and how far along the pregnancy is. It gives you a risk estimate for a couple of the more common chromosome conditions that may occur. So when you get the results from this test, you’ll get a ratio—something like a 1 out of 710 chance for baby to have Down Syndrome.  
• Another blood test that is now commonly offered is referred to as NIPT/S or Non Invasive Prenatal Testing/Screening which can be done any time after 9 weeks gestation. The biggest difference between this test and a Maternal Serum Screening is that it is much more accurate and has a lower false-positive rate. Why? Because the NIPT/S looks at cells from the placenta that have crossed over into mom’s bloodstream--and the cells that make up the placenta go on to develop into the baby, meaning they generally have the same genetic makeup as the baby. So you’re looking at fetal DNA with the NIPT/S versus just a pattern of proteins as in a Maternal Serum Screening. The results for NIPT/S will come back as either high-risk or low-risk for various conditions screened.
• Other tests that can look at the risk for chromosome abnormalities are referred to as diagnostic tests. These tests, such as the Amniocentesis or CVS (Chorionic Villus Sampling), give you information about the number and structure of all the chromosomes, and instead of giving you results as a risk estimate, they are giving you more concrete, yes-or-no information. Both tests are invasive in that they are taking a sample of either the chorionic villi from the placenta (in CVS) or the amniotic fluid surrounding baby (in amnio). While both are safe procedures, they do come with a risk of complications that could lead to miscarriage. That risk will vary per center that performs the procedure, but in general it’s anywhere from 1 out of 500 through a 1 in 1000 chance of complications that could lead to miscarriage.