Genetic Testing: Everything You Need to Know

As a parent, you hope for a healthy baby, but it’s natural to worry that your baby may be born with a genetic condition or birth defect.

Genetic testing during pregnancy can offer information about the health of your baby, so it’s worth finding out about which tests may be available to you.

Many of these tests involve routine blood work; others are more invasive. Because the choice to have a genetic test is a very personal one, know that you can turn to your healthcare provider for personalized advice.

Here’s an overview of some of the most common genetic tests and when they might be recommended during your pregnancy.

• What Is Genetic Testing?

• Why You Might Consider Undergoing Genetic Testing

• Types of Genetic Tests

• Genetic Testing by Trimester

• Genetic Tests at a Glance

• FAQs at a Glance

What Is Genetic Testing?

Genetic testing can be done to screen for certain birth defects and genetic disorders before or during your pregnancy. Some tests can help your healthcare provider confirm or rule out a particular condition, whereas others can give your provider more general information.

Genetic tests can detect conditions such as Down syndrome, spina bifida, cystic fibrosis, sickle cell anemia, Tay-Sachs disease, and thalassemias, among others.

Your healthcare provider will offer you the option of taking genetic tests, but it’s your choice whether you’d like to have them done or not.

Why You Might Consider Undergoing Genetic Testing

As you think about whether you’d like any of the genetic tests your healthcare provider offers, consider some of the following reasons for having genetic testing done:

• Screening tests don’t pose any risk to your unborn baby

• First-trimester screening tests can detect about 85 percent of Down syndrome cases

• Second-trimester screening tests can detect 80 percent of Down syndrome cases

• Combined first- and second-trimester screening tests successfully detect 94 to 96 percent of genetic disorders

• Diagnostic tests can identify more than 99 percent of many disorders; however, it’s important to keep in mind that there is a small risk of pregnancy loss associated with these procedures. During diagnostic tests a sample is taken of either amniotic fluid or the placenta.

Types of Genetic Tests

Here are some common types of genetic tests:

• Carrier screening. This test is a simple blood test that both parents can take to check if either carries specific genes for certain hereditary disorders such as Tay-Sachs disease, sickle cell disease, and cystic fibrosis, among others. The screening is usually done before you get pregnant, but it can also be done while you’re pregnant.

• Screening tests for neural tube defects or chromosomal disorders. These tests are done at different times during your pregnancy and help your healthcare provider assess the risk that your baby will have a neural tube defect (such as spina bifida) or a chromosomal disorder (such as Down syndrome). Screening tests are offered to all pregnant women and may involve a blood test, an ultrasound, or both. These tests do not put your unborn baby at risk.

• Diagnostic tests. These tests are usually recommended if a screening test result indicates your baby may be at a higher risk of certain genetic conditions. The tests are done on cells taken from your uterus. The cells are analyzed in order to form a diagnosis.

Genetic Testing by Trimester

There are a number of different tests that can be performed in either the first trimester or second trimester. Consult your healthcare provider to find out which tests are available to you, and which might be recommended for your situation.

First Trimester

Cell-Free DNA Test

This screening test is recommended for women who have a higher risk of having a baby with a chromosomal disorder (Down syndrome, trisomy 13, trisomy 18, and sex chromosome abnormalities), and/or already have a child with a chromosomal disorder.

The test involves taking a sample of your blood to assess your baby’s risk of having certain chromosomal disorders.

Combined First-Trimester Screening

This test is done between 10 weeks and 14 weeks of your pregnancy. Two different proteins are tested using a blood sample to check for Down syndrome and other conditions. This blood test is usually combined with the ultrasound exam listed below.

Nuchal Translucency Screening 

Using ultrasound, the thickness at the back of your baby’s neck is checked. An increased thickness may indicate Down syndrome.

Chorionic Villus Sampling 

Not as common as amniocentesis, chorionic villus sampling, or CVS, tests a small sample of tissue from the placenta. The test helps your healthcare provider diagnose conditions such as Down syndrome, Tay-Sachs disease, and cystic fibrosis.

The test is done between 10 and 13 weeks of your pregnancy and involves a small tube being inserted through your vagina or a needle being inserted through your abdomen to reach the uterine wall.

Second Trimester

MSAFP test 

This blood test checks the amount of maternal serum alpha-fetoprotein in your blood and helps your provider assess your baby’s risk of neural tube defects. It’s generally done between 16 weeks and 18 weeks.

Quadruple Screening Test

As the name suggests, this test screens for the presence of four proteins in your blood to evaluate your baby’s risk of having Down syndrome, trisomy 18, and neural tube defects.

This test is generally done between 15 weeks and 22 weeks of your pregnancy.

Amniocentesis 

With this diagnostic test, a sample of amniotic fluid is taken from your uterus using a long needle inserted through your abdomen. The test is performed between 15 and 20 weeks of pregnancy to check for Down syndrome and other genetic disorders as well as neural tube defects.

Combined Tests

Sometimes, the results of your tests need to be looked at together to give your healthcare provider a fuller picture of your baby’s health.

Integrated Screening

This is when your healthcare provider looks at the results from your first- and second-trimester tests together in order to assess your baby’s health.

Sequential Screening

This is when your healthcare provider looks at your first-trimester test results to assess whether to recommend additional tests.

If the results of your first-trimester tests indicate that your baby has only a low risk for a genetic disorder, she may recommend that you skip additional testing; if the risk is high, more testing may be recommended.

Genetic Tests at a Glance

For a quick look at the types of genetic tests available to you, check out the table below.

The Bottom Line

Genetic testing can be a routine part of your prenatal care. If you have any questions as to which tests you should take, turn to your healthcare provider, who can recommend what's best for your particular situation. Although optional, genetic tests can give you more information about the health of your baby, which is something to keep in mind when making your decision about taking the tests.

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