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Genetic Testing During Pregnancy: Know Your Options

July 15, 2021

From breastfeeding to day care, pregnant women must decide what’s best for themselves and their child. Genetic testing is another option to consider. When weighing the pros and cons of genetic testing, ask yourself what you think you would get out of the information, and how you would feel if you get an abnormal result.

Types of Genetic Tests 

There are two main types of prenatal genetic tests: screening and diagnostic. 

  • Screening tests can tell you the chances that a fetus has aneuploidy, meaning extra chromosomes or missing chromosomes. The consequences of aneuploidy include conditions like Down syndrome (trisomy 21). The types of genetic screening tests are: 

    • First-trimester screening, which includes an ultrasound exam and a blood test that is done between 11 weeks and 13 weeks of pregnancy.

    • Second-trimester screening, which includes an ultrasound and a “quadruple” blood test that measures the levels of four different substances in a pregnant woman’s blood and screens for Down syndrome, (trisomy 21), Edwards syndrome (trisomy 18) and neural tube defects like spina bifida. It is done between 15 weeks and 22 weeks of pregnancy.

    • Combined first- and second-trimester screening, which combines the results of the two screenings to provide information that could be more accurate than a single test result.

    • Cell-free DNA testing, which uses DNA released from the placenta into a pregnant woman’s bloodstream to screen for Down syndrome (trisomy 21), Patau syndrome (trisomy 13), Edwards syndrome (trisomy 18) and problems related to the number of sex chromosomes. It can be done starting at 10 weeks of pregnancy. 

  • Diagnostic tests can tell you if your fetus has certain disorders, rather than just the chances of having them that screenings provide. Done on cells from the fetus in the amniotic fluid or a sample from the placenta obtained through amniocentesis or chorionic villus sampling (CVS), these tests are invasive and come with a small risk of pregnancy loss. 

Before Making a Decision 

Genetic testing during pregnancy is not required. Although it’s offered to everyone, you have the option to decline any screenings or tests. 

Some questions to ask yourself and your OB-GYN before deciding on genetic screening: 

  •  If a screening test indicated that your fetus could have a genetic condition, would you want to get a diagnostic test or would you rather wait until the baby is born?

  • If a screening test showed a high risk for a genetic condition, how would you feel knowing that you're going to need further testing and that the additional test does not have the ability to give a diagnosis?

  •  Would any information you get from genetic testing help you be more prepared, or would the possibility of continued uncertainty and unknowns add to your anxiety?

  • Would confirmation of a genetic problem change your pregnancy plans? 

These are just some of the questions to discuss with your healthcare provider and/or a genetic counselor before undergoing any type of genetic test. There is no right or wrong answer to these questions, and any decision you make about screening and/or diagnostic tests is a valid one. 

The Results: What They Mean 

If you decide to undergo genetic screening tests, it’s important to know that there is a chance of false positive or false negative results with any type of genetic testing. This means no result is guaranteed to be 100 percent accurate. 

No matter which type of genetic testing you undergo, you will have the opportunity to go over the results with a healthcare provider. Together, you can decide what your next steps will be.

 

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