According to Gram Research analysis, genome sequencing of a child and both parents identified a likely genetic cause in 39.3% of 122 Chinese children with global developmental delay or intellectual developmental disorder. Most of these causes were new changes in the DNA that neither parent carried, and the results guided treatment and care changes for many families.
Developmental delays can make it hard for children to learn to walk, talk, or think at the usual pace, and finding the cause can take years. According to research reviewed by Gram, a team in China tested 122 children with these delays between 2018 and 2023 by reading the DNA of each child and both parents. The testing found a likely genetic cause in 48 children, about 39% of the group. Most of these causes were new changes in the DNA that neither parent carried. Doctors used the results to adjust care for many families, including changes to other health conditions and diet, and some families chose genetic testing for future pregnancies. The study was done at one hospital, so the results may not apply to every population, but they suggest that this type of testing can give families useful answers and practical next steps.
Key Statistics
A 2026 cohort study of 122 Chinese children with developmental delays found that trio whole-genome sequencing identified a likely genetic cause in 39.3% of cases, or 48 children.
In the same 2026 cohort study, 75% of the genetic findings were new changes that were not inherited from either parent, based on 36 of 48 diagnosed cases.
A 2026 cohort study reported that genetic results led to care changes in 57 children, including adjustments to other health conditions for 30 children and diet changes for 17 children.
The Quick Take
- What they studied: Researchers wanted to know how often a detailed genetic test, called trio whole-genome sequencing, can find the cause of developmental delays in children, and whether those results help doctors make better decisions about care.
- Who participated: The study enrolled 122 children from China who had global developmental delay or intellectual developmental disorder. These are conditions where a child is slow to reach milestones like walking, speaking, or learning. The children were followed at a single medical center from 2018 to 2023.
- Key finding: The genetic test found a likely cause in 48 of 122 children, or 39.3%. Of these causes, 36 were new changes in the DNA that were not inherited from either parent, which made up 75% of the findings.
- What it means for you: If your child has unexplained developmental delays, a genetic test that examines the child and both parents may find an answer. Finding a cause can help guide treatment, related health care, and family planning, though results vary and should be reviewed with a doctor.
The Research Details
This was a cohort study, which means researchers followed a group of people over time and recorded what happened to them. The team enrolled 122 Chinese children with developmental delays at one center and tested each child using trio whole-genome sequencing. The word trio refers to the child and both biological parents. Genome sequencing reads the full set of DNA instructions in a person’s cells, which allows researchers to look for changes that could cause the child’s condition.
After the genetic results came back, a team of specialists from different fields reviewed each case. They used the findings to change care plans where needed. The researchers then tracked what those changes led to, such as improvements in therapy, better management of other health issues, dietary adjustments, and decisions about future pregnancies.
The researchers also looked at which groups of genes were most often involved. They compared the genes linked to these conditions with known biological pathways in the brain, helping them see which brain functions were most affected.
Following patients over time shows not just whether a genetic test finds an answer, but whether that answer changes what happens to the child. This matters because a diagnosis is only useful if it leads to better care. Testing both parents also helps distinguish changes that were newly created from those passed down, which affects advice about future children.
The study was published in Clinical Genetics, a peer-reviewed journal in the field of genetics. Its group size of 122 is moderate, and it comes from only one medical center, so results may differ elsewhere. The study was not randomized, meaning it did not compare children receiving different treatments by chance. Because of this, it can show what happened after testing but cannot prove that the testing alone caused the improvements. Note that the sample size field supplied with this study lists 35, while the abstract describes 122 enrolled children. The abstract figure is used here.
What the Results Show
The main result was that trio whole-genome sequencing found a likely cause for developmental delay in 48 of 122 children, a diagnostic yield of 39.3%. In other words, roughly two in every five children tested received a clear genetic explanation for their condition. Most of the causes were small changes in single DNA letters or short sections of DNA, called SNVs and indels, with 35 cases of this type. The remaining 13 cases involved larger chunks of DNA that were missing or duplicated, known as copy number variants.
A major pattern was that 36 of the 48 findings, or 75%, were de novo changes. This means the change appeared for the first time in the child and was not inherited from either parent. Most of the inherited cases followed an autosomal dominant pattern, meaning one copy of the changed gene from one parent is enough to cause the condition. Testing both parents was what made it possible to identify these new changes.
The researchers also found that the genes linked to these conditions clustered around specific brain functions. These included how nerve cells communicate across tiny gaps called synapses, how a calming chemical signal called GABA and chloride movement work in nerve cells, and how DNA packaging is controlled to switch genes on and off. These patterns suggest where scientists may focus future research.
Genetic results led to changes in care for many children. Three children improved with a targeted therapy matched to their specific genetic change. Care for other health conditions was adjusted in 30 children. Seventeen children received changes to their diet. In addition, seven families chose preimplantation genetic testing, a process used during in vitro fertilization to screen embryos before pregnancy for the genetic change found in their family. These outcomes show that genetic results can influence daily care and family planning, not just a label on a medical chart.
Earlier studies of genome sequencing in children with developmental delays have reported diagnostic rates generally in the range of roughly 30% to 50%, and this study’s 39.3% rate falls within that range. Research has also consistently found that new changes account for a large share of cases in these conditions. What this study adds is a focus on what happens after the results come back, including care changes and family decisions, which is less often reported.
The study had a moderate number of participants and came from a single medical center, so the results may not represent all children with developmental delays. The study did not include a comparison group that received standard testing without genome sequencing, so it cannot prove that the improvements in care happened only because of the genetic test. Some outcomes, such as improvement after targeted therapy, were reported in small numbers, which makes them harder to interpret. Also, a genetic test cannot find every cause, and about six in ten children in this group did not receive a clear answer from the test.
The Bottom Line
Research shows that testing a child and both parents together can identify a likely genetic cause in about 4 in 10 children with developmental delays. Confidence in the finding that this approach finds causes is moderate to high, based on the study and related research. Confidence that these results will lead to better long-term outcomes is lower, because the study did not compare outcomes with a control group. Families should discuss with a genetic counselor or pediatric specialist whether this testing is appropriate and what the results would mean for their situation.
Parents of children with unexplained global developmental delay or intellectual developmental disorder, and clinicians who evaluate these children, should pay attention to these findings. Families who are planning future pregnancies may also find the reproductive guidance relevant. This study is less directly applicable to adults, to children whose delays have a clear known cause, or to people outside the population studied, though the general principles may apply more broadly.
A genetic test result typically returns in weeks to a few months, depending on the lab and testing process. Changes in care, such as therapy adjustments or diet changes, may begin soon after results are reviewed. Improvements in development, if they occur, often unfold over months to years, and the amount of benefit varies widely from child to child.
Frequently Asked Questions
How often does genome testing find the cause of developmental delays in children?
In a 2026 study of 122 Chinese children, trio whole-genome sequencing found a likely cause in 39.3% of cases, which is about 48 children. The test examined the child and both parents to identify the source of the condition.
What is trio whole-genome sequencing?
Trio whole-genome sequencing reads the full set of DNA instructions in a child and both biological parents. Comparing the three genomes helps identify changes in the child’s DNA that are new or inherited, which can explain developmental delays.
Why does testing both parents matter for children with developmental delays?
Testing both parents helps show whether a genetic change was passed down or appeared for the first time in the child. In the study, 75% of diagnosed cases were new changes, which affects family planning advice for future children.
Can a genetic test change how a child with developmental delays is treated?
A 2026 study found that genetic results led to care adjustments, including changes to other health conditions in 30 children and diet changes in 17 children. Three children also improved with a targeted therapy matched to their genetic change.
Want to Apply This Research?
- Log each developmental milestone your child reaches, such as first words, first steps, or completing a simple puzzle, along with the date and any therapy sessions attended. Recording these weekly helps you and your care team see patterns over time and notice whether progress is changing after new care steps.
- Use the app to set a reminder for each medical appointment, therapy session, or dietary change recommended by your care team. Record any questions you want to ask about genetic results so you can bring a written list to your next visit.
- Review your milestone log and care notes every three months with your child’s doctor. Over the long term, keep a running record of genetic counseling visits, test results, and family planning decisions so that the information stays organized as your child grows and new medical questions come up.
This article summarizes a single research study and is for general education only. It is not medical advice and does not replace consultation with a doctor, genetic counselor, or other qualified health professional. Genetic testing decisions, including whether to test a child or family members, should be made with professional guidance that takes into account individual medical history and family circumstances.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.