Why Would a Child Need Genetic Testing?

Children undergo genetic testing when doctors suspect that a health problem has roots in their DNA. The reasons range from unexplained developmental delays and birth defects to childhood cancers, severe epilepsy, and mysterious illnesses in newborn intensive care units. In some cases, testing clarifies a diagnosis that has eluded doctors for years; in others, it directly changes which medications a child receives or which therapies are pursued. The circumstances are varied, but the core logic is the same: when a child’s condition doesn’t fit a straightforward clinical explanation, the answer may be written in their genome.

Unexplained Developmental Delays and Unusual Physical Features

One of the most common reasons a pediatrician refers a child for genetic testing is a developmental delay that doesn’t have an obvious cause. A toddler who isn’t meeting milestones for speech, motor skills, or social interaction, especially if they also have unusual facial features or other physical differences, is a strong candidate. Chromosomal microarray analysis has become a first-line diagnostic tool for children with intellectual disability, autism spectrum conditions, and dysmorphic features because of its high rate of identifying a genetic explanation.¹ For pediatricians, certain physical signs serve as red flags: an unusually shaped head, widely spaced eyes, low-set ears, a single palmar crease, or limb differences. When several of these features appear together, a genetic syndrome becomes a leading possibility, and testing helps narrow the field.²

This kind of testing isn’t just about labeling a condition. A confirmed genetic diagnosis can unlock access to targeted therapies, connect families with condition-specific support groups, and alert doctors to associated health risks they should monitor, such as heart defects or kidney problems that sometimes accompany certain syndromes.

Critically Ill Newborns

Some of the most urgent genetic testing happens in neonatal and pediatric intensive care units. A baby born with unexplained organ failure, severe metabolic crises, or multiple congenital anomalies may have a genetic disorder that requires immediate, specific treatment. Rapid whole-genome sequencing has emerged as a first-line test for these critically ill infants, because speed matters enormously when a child is on life support and doctors are choosing between treatment paths.³

In a study of acutely ill infants, rapid sequencing achieved a high rate of genetic diagnoses, and most of those diagnoses directly changed how the infant was managed in the ICU.⁴ In practice, that might mean switching from a general treatment plan to one that targets the specific metabolic pathway involved, or in some heartbreaking cases, it means recognizing a condition that has no effective treatment, allowing families and medical teams to make informed decisions about palliative care rather than continuing invasive procedures.

Following Up on Newborn Screening

Every baby born in the United States and many other countries gets a heel-prick blood test within the first couple of days of life. This newborn screening catches a range of metabolic, endocrine, and blood disorders early enough for treatment to prevent serious harm. But the biochemical tests used in standard screening produce some false positives and false negatives. When a result comes back abnormal, genetic testing often serves as the confirmatory step, pinpointing whether the child actually carries the disease-causing variant or whether the initial flag was a false alarm.⁵

Genetic screening can also identify conditions that traditional biochemical tests miss entirely, and it helps weed out false positives caused by factors like how the baby was delivered or whether they were premature.⁶ For parents, this means fewer unnecessary follow-up appointments and less anxiety when a newborn screen flags something that turns out to be nothing. At the same time, combining genetic and biochemical screening catches more real cases, which is exactly the point of screening in the first place.

Childhood Epilepsy and Treatment Decisions

Epilepsy is one of the areas where genetic testing most clearly changes what doctors do next. Many forms of childhood epilepsy have a genetic basis, and knowing the specific gene involved can guide which anti-seizure medications to use and which to avoid. In a study of children who received a genetic diagnosis for their epilepsy, the diagnosis changed medical management for about seven in ten patients. Treatment was directly affected in close to half of them, including changes to seizure medications, the introduction of vitamin or metabolic therapies, or enrollment discussions for gene-specific clinical trials.⁷

This is not a small deal. Some genetic epilepsies respond beautifully to a specific drug but get worse on another drug that would be a standard first choice. Without the genetic result, a child might cycle through multiple medications that don’t work or cause unnecessary side effects. The genetic result can also give families a clearer picture of what to expect, whether the epilepsy is likely to be lifelong and severe, or whether there’s a reasonable chance of improvement.

Pediatric Cancer

Genetic testing in pediatric oncology works a bit differently from testing for inherited conditions. Here, doctors are often profiling the tumor itself to look for mutations that drive the cancer’s growth. In a large prospective study of children with solid tumors, molecular profiling found that the vast majority, roughly 86%, carried at least one genomic alteration with potential impact on care. About two-thirds of patients had alterations with diagnostic significance, and 65% had alterations that could be matched to a targeted therapy.⁸

Targeted therapies attack cancer cells based on their specific molecular profile rather than using a one-size-fits-all chemotherapy approach. For a child with cancer, this can mean a treatment that is both more effective and less toxic. Genetic testing of the tumor can also reclassify the type of cancer a child has, which sometimes changes the treatment protocol entirely.

Choosing the Right Medication

Beyond epilepsy and cancer, a growing area called pharmacogenomics uses genetic testing to predict how a child will metabolize certain drugs. Children vary widely in how their bodies process medications, and some of that variation is genetic. In child and adolescent psychiatry, for example, pharmacogenomic testing may help predict treatment response and side effects for medications used to treat ADHD, depression, and anxiety.⁹

When this testing was implemented at one pediatric hospital, the results warranted treatment adjustments for about a third of the children tested, meaning the standard drug or dose was not the best fit for their genetic makeup.¹⁰ For the remaining two-thirds, testing confirmed that the standard regimen was fine. Either way, the result is useful: you either adjust or you gain confidence that the current plan is right.

Ending the Diagnostic Odyssey

Many families spend years bouncing between specialists, undergoing test after test, without ever getting a clear diagnosis for their child’s condition. Clinicians call this the “diagnostic odyssey,” and it is exhausting emotionally, logistically, and financially. Traditional approaches where a geneticist picks tests based on the child’s symptoms only reach a diagnosis in fewer than half of patients.¹¹ The remaining families are left in limbo.

Broader genomic sequencing has significantly improved these odds. A meta-analysis of pediatric patients with rare and undiagnosed diseases found that genome-wide sequencing achieved a pooled diagnostic yield of about 34%, compared to roughly 18% for non-genome-wide approaches, giving children about 2.4 times the odds of finally receiving a molecular diagnosis.¹² Across a broader set of studies, whole-genome and whole-exome sequencing both substantially outperform older chromosomal microarray testing in diagnostic power.¹³

Even when an initial round of exome sequencing comes back negative, it is worth revisiting. Periodically reanalyzing old sequencing data with updated knowledge can yield new diagnoses, because researchers are constantly discovering new gene-disease connections. One meta-analysis found that reanalysis of previously negative exome results produced a diagnostic rate comparable to running a fresh whole-genome sequence, around 14% versus 24% overall for genome sequencing in the same group of patients.¹⁴ The practical takeaway is that a negative genetic test today doesn’t necessarily mean a dead end forever.

When the Result Is Uncertain

Not every genetic test delivers a clear positive or negative. A common outcome is a “variant of uncertain significance,” or VUS, meaning the lab found a genetic change but can’t yet say whether it causes disease. As genomic sequencing has become more widely used in pediatric medicine, VUS results have become increasingly frequent.¹⁵ This can be deeply frustrating for families who were hoping for answers.

The good news is that VUS classifications aren’t permanent. As more research accumulates, many of these uncertain findings get reclassified. In one study of children with inherited heart rhythm disorders, over half of the variants initially labeled uncertain were reclassified when newer criteria were applied, with about a third being upgraded to disease-causing and a smaller fraction downgraded to harmless.¹⁶ The challenge is that no standardized system exists for tracking these variants and prompting reinterpretation. Families may need to advocate for periodic review of their child’s results, and genetic counselors report that patients being lost to follow-up is the single biggest barrier to getting VUS results revisited.

The Emotional Weight of Testing

Getting a genetic diagnosis for your child is not a simple transaction. For many parents, it brings a complicated mix of relief and grief. Relief because the years of searching are over, grief because the diagnosis often confirms that their child’s condition is permanent and, in some cases, progressive. In families of children with severe epilepsy syndromes, parents reported that the lack of specific information about what their child’s particular genetic diagnosis meant for the future, combined with limited psychological support, contributed to ongoing stress.¹⁷

Parents of children diagnosed with mitochondrial disease described the diagnosis as both valuable and empowering, because it helped focus management decisions and ended the uncertainty. But many also felt overwhelmed navigating the health care system afterward and reported a serious impact on their romantic relationships.¹⁸ The takeaway is that genetic testing doesn’t end at the lab report. Families benefit enormously from genetic counseling and psychological support before, during, and after the process.

Ethical Questions Around Testing Children

Genetic testing in children raises ethical issues that don’t come up in the same way for adults. An adult can weigh the pros and cons of learning their own genetic information and consent fully. A young child cannot. Professional organizations in genetics and pediatrics have grappled with questions like whether it’s appropriate to test a child for conditions that won’t affect them until adulthood, how to handle unexpected secondary findings that reveal risk for diseases the family wasn’t asking about, and what role informed consent should play in newborn screening.¹⁹

The general principle most guidelines follow is that testing a child is appropriate when the result will lead to a meaningful change in their medical care during childhood. Testing a five-year-old for a gene linked to a cancer risk that wouldn’t manifest until their 40s is harder to justify, because it removes the child’s future right to decide for themselves whether they want that information. The genetic counselor’s role in pediatric settings is to navigate this tension, balancing the parents’ desire for information with the child’s right to an “open future” where they eventually make their own choices about genetic knowledge.²⁰

Access Is Not Equal

For all its promise, pediatric genetic testing isn’t equally available to every family. Families in rural areas, those with lower incomes, and those from underrepresented racial and ethnic groups face significant barriers to accessing genomic medicine. The infrastructure for genetic testing, including genetic counselors, specialized labs, and physicians trained in genomics, is concentrated in large academic medical centers in urban areas.²¹

Insurance coverage varies widely. Some plans cover broad genomic sequencing for children with suspected rare diseases, while others will only cover narrow, targeted tests, even when broader testing would be more efficient and cost-effective. Telehealth-based genetic counseling and regional partnerships with academic centers are emerging as partial solutions, but the gap remains real. A child’s chance of getting the right genetic test at the right time still depends too much on where they live and what insurance their family carries.

Direct-to-Consumer Tests and Why They Are Different

Some parents turn to direct-to-consumer genetic tests, the kind you order online and do with a saliva kit at home, hoping for health insights about their child. These tests can be interesting for ancestry information and a handful of well-studied traits, but they are fundamentally different from clinical genetic testing ordered by a doctor. Clinical tests examine specific genes in depth, are performed in certified laboratories, and are interpreted by trained geneticists or genetic counselors in the context of the child’s medical history. Direct-to-consumer products typically scan a limited set of genetic markers and provide results without the clinical context needed to act on them safely. The risk of misinterpreting results, either by missing something important or by raising alarm over something clinically meaningless, is real enough that clinicians are encouraged to guide families through the limitations of these products.²²

If you’re a parent who has received a concerning result from a consumer test, the right next step is to bring it to your child’s doctor. A clinical-grade test can confirm or rule out whatever the consumer test flagged, and a genetic counselor can help you understand what the result actually means for your child’s health. Consumer tests are a starting point at best, never a substitute for the real thing.