What is prenatal genetic testing?

Prenatal genetic testing, also called fetal genetic testing, is performed during pregnancy to give parents important information about whether their baby may be born with certain genetic disorders. These are conditions that develop due to changes in genes or chromosomes.

Some of these genetic conditions can be inherited, while others are not. Inherited disorders run in families and occur due to changes in genes called mutations—in most cases, both parents must be carriers of the gene. Other conditions are caused by missing or extra chromosomes.

All pregnant women have the option of having prenatal genetic testing. You can discuss your choices with your OBGYN or maternal-fetal medicine specialist at Baylor Scott & White to help you decide whether genetic testing is right for you.

pregnant woman and her OBGYN discussing prenatal genetic testing

What are the types of prenatal genetic tests?

There are two main types of testing for genetic conditions during pregnancy.

Prenatal screening tests

Prenatal screening tests can assess the likelihood of your baby having certain genetic conditions. These tests are typically offered during the first or second trimester, including blood tests and ultrasounds. Irregular results from a screening test do not necessarily mean your baby has a genetic condition. Your healthcare provider can help you determine if you need diagnostic tests.

Prenatal diagnostic tests

Diagnostic tests are the only definitive way to determine if your baby has a genetic condition. You may choose to undergo a diagnostic test if a screening indicates a higher risk of a genetic condition. Additionally, you might consider a diagnostic test if factors such as your age, family history or health history elevate your baby's risk.


What types of prenatal screening tests may be available?

Screening tests do not diagnose genetic conditions; an abnormal result simply indicates a higher risk for a genetic disorder rather than confirming one. Your healthcare provider can help interpret the results of genetic screening tests and discuss the next steps. In some cases, they may recommend diagnostic testing for further evaluation.

Carrier screening

Carrier screening can be done before or during pregnancy. Performed using blood samples or cheek swabs, carrier screening can help determine if you and your partner are at an increased risk of having a baby with a specific inherited disorder, such as cystic fibrosis or spinal muscular atrophy. Early insight can help you better prepare for the future.

What types of prenatal diagnostic tests are available?

Diagnostic prenatal tests can confirm whether the fetus has a genetic condition. These tests involve collecting cells from the amniotic fluid or placenta to screen for specific disorders. Diagnostic testing is usually only performed when a screening test shows abnormal results or if you are at high risk for having a baby with a genetic condition.

Why might I choose to have genetic testing during pregnancy?

While it is your choice whether to have genetic testing, your provider might recommend it based on several factors. 

These include:

  • Abnormal ultrasound results
  • Being a known carrier of a genetic condition
  • Having a family history of a genetic condition or another child diagnosed with a genetic condition
  • Screening test results that indicate the possibility of a genetic condition
  • Your age (the older you are, the higher the chances you could have a baby with a genetic condition)
  • History of miscarriage or stillbirth

Understanding the results

Screening tests provide genetic information that indicates the level of risk that a certain genetic condition might be present. A positive result means your baby is at higher risk of having the condition than the general population, while a negative result means your baby is at lower risk for having the condition, but there is still a small chance the condition could be present.

Your healthcare provider or a genetic counselor will discuss screening test results with you and help you determine whether you would like to have diagnostic testing with amniocentesis or CVS.

When a diagnostic test result is negative, this means your baby does not have the disorder that was tested for. However, there is still the possibility a different genetic disorder could be present.

A positive diagnostic result means your baby has the condition that was tested for. Your OBGYN, a genetic counselor or a specialist in the condition can help you understand the condition, what types of care your baby may need and what your options are. In some cases, you can have a specialized ultrasound to get more detailed information about your baby’s condition and whether it is mild or severe.

doctor discussing the results of prenatal genetic testing with patients