Prenatal genetic testing explained: Is it right for you?

Expecting a child comes with numerous decisions, one of the most significant being whether to undergo prenatal genetic testing.

Prenatal genetic testing can help you prepare for what lies ahead, whether by making lifestyle changes, considering further medical interventions, or exploring early treatment options. For some, it provides peace of mind — for others, it might uncover risks that require careful planning.

Still, understanding the practical benefits and risks of prenatal genetic testing can help you make an informed choice. This article breaks down the key aspects you should consider, including what the test reveals, who should consider it, and how it may impact your pregnancy.

What is prenatal genetic testing?

Prenatal genetic testing screens for genetic disorders or chromosomal abnormalities in a developing fetus to identify conditions such as Down syndrome and cystic fibrosis. While these tests are optional, they are highly recommended, especially if you are over 35, as the risk of certain conditions increases with age.

These tests assess the risk of genetic conditions early in pregnancy, helping you prepare for potential medical or emotional challenges. If a health issue is identified, you can seek medical care and support. Genetic testing also informs family planning, especially for couples with a history of genetic disorders or other risk factors.

Benefits and risks of prenatal genetic testing

Like most medical decisions, prenatal genetic testing comes with both benefits and risks. The table below outlines key advantages and potential drawbacks you should consider:

How is prenatal genetic testing done?

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The two main types of prenatal genetic testing are screening and diagnostic tests. In the sections below, we’ll explain how they differ and what each can tell you about your baby’s health.

Screening tests

Prenatal screening tests are designed to assess the risk of genetic disorders without providing a definitive diagnosis. These tests help you understand the likelihood of certain conditions, offering valuable insights for making informed decisions.

One such option is the first-trimester combined screening, performed between the 11th and 14th week of pregnancy. It involves a blood test and a nuchal translucency (NT) ultrasound to evaluate the risk of Down syndrome and Edwards syndrome by analyzing specific markers in the blood and ultrasound results.

The maternal serum screening, also known as quad screen, is commonly performed between the 15th and 20th week of pregnancy. This blood test measures four proteins — alpha-fetoprotein (AFP), estriol, human chorionic gonadotropin (hCG), and inhibin-A — to assess the baby’s risks for Down syndrome, neural tube defects, and other abnormalities.

For greater accuracy, non-invasive prenatal testing (NIPT), or cell-free fetal DNA testing, is another option you can consider after 10 weeks of pregnancy. This blood test analyzes fetal DNA found in your bloodstream to screen for chromosomal abnormalities. NIPT also provides information about the fetal sex, offering further clarity.

Diagnostic tests

Diagnostic tests confirm whether a fetus has a specific genetic disorder by analyzing fetal cells or amniotic fluid. Unlike screening tests, which only assess risk, these tests provide a definitive diagnosis. 

For example, chorionic villus sampling (CVS) is performed between the 11th and 12th week of pregnancy. It involves taking a small sample of tissue from your placenta to test for chromosomal abnormalities like Down syndrome and inherited genetic disorders such as cystic fibrosis. 

Amniocentesis is another option that is conducted between the 15th and 18th week of pregnancy. A needle is used to draw an amniotic fluid sample containing fetal cells, which are tested for genetic conditions, including chromosomal abnormalities like Down syndrome and neural tube defects. Like CVS, amniocentesis carries a small risk of miscarriage.

The table below shows a list of other common conditions that you can screen for with prenatal genetic testing:

Bonus read — Understand what carrier screening is and how it can assist in ensuring a healthy family:

• What is carrier screening?

• 7 benefits of doing carrier screening

Who should consider prenatal genetic testing?

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Prenatal genetic testing helps provide clarity about potential health risks for your baby. While the decision to undergo testing is personal, certain factors may make it more suitable for some expectant parents, such as:

• Advanced maternal age: Women aged 35 or older at their due date are generally recommended to consider prenatal genetic screening due to an increased risk of chromosomal abnormalities.

• Family history of genetic disorders: Couples with a history of genetic conditions in their families or those who already have a child with a genetic condition should consider genetic counseling and testing. This includes conditions like cystic fibrosis, Tay-Sachs disease, and sickle cell disease.

• Abnormal screening results: Pregnant women who receive worrying results from initial screening tests should consider further diagnostic testing to assess the risk of birth defects.

• Ultrasound findings: If an ultrasound reveals potential fetal abnormalities, further genetic testing may be advised to understand the implications better.

• Exposure to harmful substances: Those exposed to harmful substances or medications that could affect fetal development should discuss testing options with their healthcare provider.

• Personal preference and anxiety: Ultimately, any pregnant woman who desires more information about her fetus's health may consider prenatal genetic testing. The decision depends on individual circumstances, including how much information one wishes to know about potential health issues.

• Multiple miscarriages: A history of miscarriages can indicate a higher risk of genetic health issues.

What to do after prenatal genetic screening

After prenatal genetic screening, the next steps depend on your results. A clear plan is essential if the screening indicates a potential risk or is unclear, and your doctor may recommend a definitive diagnostic test like amniocentesis or chorionic villus sampling.

If a risk or condition is confirmed, you can start planning for medical care, adjusting your birth plan, and coordinating with specialists. Some conditions can be treated in utero, while others require specialized post-birth care.

Consulting a genetic counselor is also wise, as they can provide invaluable support during this time by helping you to:

• Understand your test results: They can explain what the results mean in the context of your pregnancy.

• Clarify potential outcomes: A genetic counselor will discuss possible outcomes based on the condition, including the likelihood of various health scenarios.

• Navigate emotional and ethical concerns: Facing a genetic diagnosis can be emotionally challenging. A counselor can help you manage any stress or difficult feelings that arise.

• Decide on further steps: Based on the information you receive, the counselor can help you determine whether additional tests are needed and guide you through options for managing your pregnancy moving forward.

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How accurate is prenatal genetic testing?

The accuracy of prenatal genetic testing can vary depending on the type of test you take and the conditions you’re testing for. 

Non-invasive prenatal testing is highly effective at detecting common chromosomal abnormalities, such as Down, Edwards, and Patau, with an accuracy rate of over 99%. Still, while NIPT is accurate for these major conditions, its effectiveness may be lower when screening for less-known genetic mutations.

Despite their high accuracy, screening tests like NIPT still have a slight chance of producing a false positive or false negative result. Maternal weight, gestational age, and multiple pregnancies can influence the results.

If a screening test suggests a potential abnormality, diagnostic tests like CVS or amniocentesis can provide a more definitive diagnosis. Although these diagnostic procedures are invasive, they offer nearly 100% accuracy and can confirm whether a genetic condition is present.

Source: Tima Miroshnichenko

False positives and false negatives

False positives and false negatives are important considerations in prenatal screening tests, as understanding these outcomes helps manage expectations and guides the next steps in testing or care.

False positives occur when a screening test indicates a risk for a condition that isn’t present. For example, a screening test might suggest a higher risk for Down syndrome when the baby is, in fact, unaffected, causing anxiety and leading to unnecessary follow-up tests.

In contrast, false negatives occur when a screening test fails to detect a condition that is present. While rare, these can happen, especially if the test can’t capture sufficient fetal DNA, meaning a genetic condition may still exist even with a “low-risk” result.

Targeted prenatal testing vs. whole-genome sequencing (WGS)

Prenatal genetic testing offers valuable insights into potential health issues, allowing for early detection of specific risks. These tests are highly targeted, focusing on a limited number of genetic conditions and providing you with crucial information to guide your pregnancy.

In contrast, whole-genome sequencing (WGS) provides a broader screening option for parents looking to understand their genetic risks before pregnancy. 

Unlike prenatal genetic tests that assess the baby's genetic health, WGS examines the parents' entire genetic code to identify potential carrier risks. This information helps you understand what conditions you could pass on to your children.

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Nucleus Family offers preconception genetic testing through an easy, at-home, non-invasive test. While not a diagnostic tool, Nucleus provides clinical-grade insights and personalized genetic counseling, empowering you to make informed decisions for your family's health.

Nucleus: A whole-genome test for future families

Nucleus is a cutting-edge genetic platform that uses whole-genome sequencing to analyze your DNA in detail. Unlike commercial tests that examine only a small fraction of your genome, Nucleus sequences nearly all 6 billion data points in your DNA, offering a deeper, more complete understanding of your genetic predispositions.

With Nucleus, you can undergo extensive genetic screening to identify potential hereditary conditions before pregnancy. The test delivers a full suite of genetic insights, including:

• Carrier status for 900+ inherited conditions that could be passed to your child, such as muscular dystrophy

• Your own health risks for chronic and genetic conditions like heart disease, diabetes, and certain cancers

• Pharmacogenomic insights that reveal how your genes may affect your response to medications

• Diet and lifestyle-related genetic markers that can help you make informed health choices during pregnancy

• Traits and characteristics linked to your DNA, such as nutrient metabolism, lactose tolerance, and more

Nucleus reports are clear, actionable, and designed for easy interpretation, helping you prepare for pregnancy. The platform provides continuous updates, ensuring your insights evolve with the latest scientific advancements. 

If you need further support, Nucleus provides access to board-certified healthcare professionals through SteadyMD. Additionally, Nucleus integrates AI-powered insights, offering personalized health recommendations that make your genetic data even more useful.

Nucleus is HIPAA-compliant and CAP-CLIA certified, guaranteeing secure, private, and accurate testing. Your data is safeguarded with the highest industry standards. 

How to get started with Nucleus

Getting started is simple:

1. Sign up for Nucleus Family

2. Provide your personal information

3. Order the test kit

Once you receive the test kit, swab your cheek, send the sample back using the pre-paid, pre-labeled envelope, and access your results in 6–8 weeks through an intuitive online portal.

For just $399, Nucleus provides the test kit, shipping, and full access to your reports. It's also FSA/HSA eligible, helping you lower out-of-pocket costs.

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Featured image source: olia danilevich