Your child has a diagnosis. Autism, cerebral palsy, global developmental delay. The pediatrician mentions genetic testing. You're not sure what that means or whether it changes anything.

Genetic testing after a developmental diagnosis isn't about confirming what you already know. It's about finding out whether there's an underlying genetic cause that could affect treatment decisions, connect you to clinical trials, or inform family planning. For some families, it provides answers. For others, it rules out specific conditions. And for many, the results are inconclusive.

Here's what each type of genetic test can tell you, what it costs, and when it's recommended.

Why Genetic Testing Matters After a Diagnosis

A diagnosis like autism or cerebral palsy describes your child's symptoms and developmental pattern. It doesn't always explain the root cause. Genetic testing looks for changes in chromosomes or genes that could be driving those symptoms.

Finding a genetic cause can open doors you didn't know existed. A specific genetic diagnosis may qualify your child for clinical trials testing new therapies. It can guide medical monitoring for related health issues that appear with certain genetic conditions. And if a genetic variant is identified, siblings and future pregnancies can be screened.

But genetic testing doesn't always find a cause. A genetic variant is identified in fewer than 25% of autism cases, around 32% of cerebral palsy cases when the cause isn't clear, and 36-53% of unexplained global developmental delay or intellectual disability cases. Those numbers matter because they set realistic expectations.

When testing comes back without findings, it doesn't mean the diagnosis is wrong or that you missed something. It means the cause is either not genetic or involves genetic changes we can't detect yet with current testing methods.

The Three Main Types of Genetic Tests

Not all genetic tests look for the same things. Each has a different scope, cost, and likelihood of finding a cause.

Chromosomal Microarray (CMA)

CMA detects large deletions or duplications of genetic material across all chromosomes. Think of it as scanning for missing or extra chunks of DNA rather than reading individual genes letter by letter.

CMA finds a genetic cause in about 10-20% of autism cases and is recommended as a first-tier test by the American Academy of Pediatrics for children with global developmental delay or intellectual disability.

Cost: $300-$600 before insurance. Most insurance plans cover it when ordered for developmental concerns.

What it misses: Single-gene mutations, small changes within genes, and changes outside large structural chromosome abnormalities.

Whole Exome Sequencing (WES)

WES reads the protein-coding regions of all your genes. That's about 1-2% of your entire genome, but it includes the areas where most disease-causing mutations occur.

WES identifies a genetic variant in roughly 30-40% of autism cases and 36-53% of unexplained developmental delay or intellectual disability. For cerebral palsy when imaging and history don't point to an obvious cause like prematurity or birth injury, WES finds a genetic explanation in about 32% of cases.

The AAP's updated 2025-2026 guidelines recommend WES or whole genome sequencing as first-tier testing for global developmental delay and intellectual disability, often alongside or instead of CMA.

Cost: $1,000-$2,500 before insurance. Insurance coverage has improved significantly as WES becomes standard practice, but prior authorization is often required.

What it misses: Non-coding regions of the genome, large structural changes that CMA would catch, and variants that current science hasn't yet linked to disease.

Whole Genome Sequencing (WGS)

WGS reads your entire genome, not just the protein-coding regions. It's the most comprehensive option and catches everything WES would find plus changes in non-coding areas that regulate gene activity.

WGS identified variants in about 34% of autism cases in one large study published in Nature. It's more likely to find uncertain findings than WES because it's looking at so much more genetic material.

Cost: $3,000-$8,000 before insurance. Coverage is inconsistent and often limited to cases where WES came back negative.

What it misses: Nothing in terms of genetic sequence, but interpreting what the findings mean is harder because much of the non-coding genome's function isn't fully understood yet.

Fragile X Testing: A Specific First-Tier Recommendation

Fragile X syndrome is the most common inherited cause of intellectual disability and can present with autism-related behaviors. Testing for Fragile X is part of the standard first-tier genetic evaluation for children with developmental delays or autism, especially boys.

The test looks for a specific mutation in the FMR1 gene on the X chromosome. It's a simple DNA test, costs less than $200-$400, and is almost always covered by insurance when developmental concerns are documented.

If your child is being evaluated for autism or developmental delay and Fragile X testing hasn't been offered, ask about it.

What Results Mean

Genetic test results fall into three categories.

Positive: A genetic change known to cause disease is identified. This is the clearest result. It may explain your child's symptoms, guide medical management, and inform family planning.

Variant of uncertain significance (VUS): A genetic change was found, but science hasn't determined whether it causes disease. VUS results are common and don't provide actionable answers. They're frustrating, but they're not the same as a negative result. As research advances, some VUS get reclassified as pathogenic or benign.

Negative: No disease-causing genetic changes were detected. This is the most common result. It doesn't rule out a genetic cause entirely, it just means current testing methods didn't find one.

For a deeper look at VUS results and trio testing, where your child is tested alongside both parents to clarify uncertain findings, see Genetic Testing for Developmental Delays: What the New AAP Guidelines Mean for Your Family.

When Is Genetic Testing Recommended?

The AAP recommends genetic testing for children with:

• Global developmental delay or intellectual disability of unknown cause
• Autism spectrum disorder
• Multiple congenital anomalies
• Features suggestive of a specific genetic syndrome

For cerebral palsy, genetic testing is increasingly recommended when the cause isn't obvious from imaging or birth history. If your child's CP doesn't fit the typical profile of prematurity, hypoxic event, or abnormal brain MRI, genetic testing may identify an underlying cause that changes monitoring or treatment plans.

Insurance typically covers genetic testing when it's ordered based on documented developmental concerns and follows AAP guidelines. Prior authorization is standard for WES and WGS.

Should You See a Genetic Counselor?

Yes. Genetic counseling isn't just for families planning pregnancies. It's recommended for all families of children with autism spectrum disorder or developmental delays, and many families don't know counseling applies after diagnosis.

A genetic counselor explains which tests make sense for your child's situation, what the results could tell you, and what they won't. They walk through costs, insurance coverage, and what to expect from the process. After results come back, they interpret findings and explain next steps.

Most children's hospitals and large pediatric practices have genetic counselors on staff. If your pediatrician mentions genetic testing but doesn't refer you to counseling, ask for a referral.

What Happens If a Genetic Cause Is Found

A genetic diagnosis can shift your child's care plan in specific ways.

Some genetic conditions come with established medical protocols. If your child is diagnosed with a known syndrome, there may be screening guidelines for heart issues, kidney function, or other organ systems that require monitoring.

A genetic diagnosis may qualify your child for clinical trials testing new treatments. The first personalized CRISPR gene therapy was delivered to an infant with CPS1 deficiency in February 2025 at UCSF's new $20 million Center for Pediatric CRISPR Cures. While CRISPR treatments for most developmental conditions are years away, having a confirmed genetic diagnosis is often a prerequisite for trial enrollment when those therapies do reach pediatric populations.

And if the genetic variant is inheritable, siblings can be tested and future pregnancies can be screened if you choose.

What Happens If Testing Comes Back Negative

Most families don't get a genetic diagnosis. That doesn't mean testing was pointless.

A negative CMA or WES result rules out the most common genetic causes and narrows the diagnostic focus. It tells your care team to look elsewhere: metabolic issues, environmental factors, or causes we don't yet understand.

You continue with the same therapies and interventions your child was already receiving. The diagnosis remains accurate whether it's autism, cerebral palsy, or global developmental delay. You just don't have a genetic explanation for it yet.

Some families choose to bank DNA samples for future testing as new genes are discovered and testing methods improve. Ask your genetic counselor if that's an option.

Cost and Insurance Coverage

Costs vary widely depending on the test and the lab.

• Chromosomal microarray: $300-$600
• Fragile X testing: $200-$400
• Whole exome sequencing: $1,000-$2,500
• Whole genome sequencing: $3,000-$8,000

Insurance coverage has improved as genetic testing becomes standard practice, especially for CMA and WES. Most plans cover testing when ordered based on AAP guidelines and documented developmental concerns, but prior authorization is required for WES and WGS.

If your insurance denies coverage, genetic counselors can help with appeals and may know about lab-specific financial assistance programs that cap out-of-pocket costs at $100-$300 for qualifying families.

The Decision Is Yours

Genetic testing isn't mandatory. Some families pursue it immediately after diagnosis. Others wait. Some decide testing won't change their child's care plan enough to be worth it.

What matters is that you have the information to make that call. Talk to your pediatrician or a genetic counselor about which tests make sense for your child's condition, what results could realistically tell you, and what the costs look like with your insurance.

Genetic testing is one tool. It provides clarity for some families and opens specific doors for others. And when it doesn't find a cause, it's still narrowing the field.