Apr 13, 2016 - Health + Traits

Genetic Testing Pre-Pregnancy

By Erynn Gordon, MS, LCGC
23andMe’s Director of Clinical DevelopmentErynn2 cropped (b_w)-1

Testing in pregnancy can be a little overwhelming for prospective parents – blood tests, glucose challenge, ultrasounds, fetal nonstress tests. Many of these tests  are offered with little explanation but rather the expectation that you’ll proceed for the health of your baby.

But as a genetic counselor, and a mother, I know that all these tests can be overwhelming. One particular type of testing that warrants more attention before pregnancy is carrier status testing for genetically inherited conditions.

I’m a big proponent of genetic testing and I think the best time to be tested is prior to a pregnancy. Genetic testing pre-pregnancy allows a couple to learn about their carrier status; if they are carriers they have the luxury of time to learn about the disease risk and discuss it with their healthcare provider.
Carrier Status Variants

So what are carrier status tests?

Carrier status tests are a type of genetic test used to find out if you carry a genetic change – or variant. For the types of conditions included in a carrier status test, having one genetic change – being a carrier – typically doesn’t mean you will have that condition, but you could pass on the variant to your child.

For autosomal recessive disorders, the types of conditions that healthcare provider are looking for when they do a carrier status test, it is only when both parents are carriers for the same condition that the child has a 1 in 4, or 25 percent, chance to be affected with the condition. (It’s important to note that this also means that they have a 75 percent chance that their child will not be affected.) Autosomal recessive conditions for which carrier testing is commonly offered by healthcare providers include cystic fibrosis, Tay Sachs disease and sickle cell anemia, among many others.

What can you do if both you and your partner are carriers?

If both you and your partner are carriers you should speak to your doctor or healthcare professional to fully understand your options.

Women who are interested in carrier testing can talk to their gynecologist or obstetrician to learn about available options. In many cases, carrier testing is offered based on a woman’s ethnic background.

For example, women of African descent may be offered carrier status testing for sickle cell anemia.  

Women of European descent may be offered testing for cystic fibrosis.  Standard recommendations for carrier status testing are based on what disorders are most common in each population.  Historically, because of the high cost of genetic testing, these targeted tests made sense. But now, because of  the dropping cost of genetic testing, it is feasible to test for genetic conditions more broadly.  This broader approach means that even women who do not have a lot of information on their ancestry but want to have carrier status testing done, are no longer limited based on knowledge of their family background.  

Broad-based carrier testing, sometimes referred to as pan-ethnic carrier testing, is available through traditional healthcare providers as well as direct-to-consumer.

Direct-to-consumer genetic tests, such as the carrier status test offered by 23andMe* can provide valuable insights that can help start the conversation with your healthcare provider about appropriate genetic screening. At this time, no genetic test covers every possible risk to your future children so whether you choose direct-to-consumer testing or you have testing through your healthcare provider, be sure to ask about the limitations of the test so that you understand what the test can tell you and what it can’t.

Have more questions? Consider talking with a genetic counselor.  You can find a local genetic counselor through the National Society of Genetic Counselors.

* 23andMe tests can be used to determine carrier status in adults from saliva collected using an FDA-cleared collection device (Oragene-DX model OGD-500.001), but cannot determine if you have two copies of the genetic variant. Each test is most relevant for people of certain ethnicities. The tests are not intended to diagnose a disease, or tell you anything about your risk for developing a disease in the future. On their own, carrier status tests are not intended to tell you anything about the health of your fetus, or your newborn child’s risk of developing a particular disease later in life. The Cystic Fibrosis carrier status test is indicated for the detection of 28 variants in the CFTR gene and is most relevant for people of Ashkenazi Jewish, European, and Hispanic/Latino descent. The Tay-Sachs Disease carrier status test is indicated for the detection of 4 variants in the HEXA gene and is most relevant for people of Ashkenazi Jewish and Cajun descent. The Sickle Cell Anemia carrier status test is indicated for the detection of the HbS variant in the HBB gene and is most relevant for people of African descent.

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