Pediatricians have little to go on in assessing when children with Down syndrome should walk, talk and achieve other milestones. Now, a new study is detailing benchmarks specific to those with the chromosomal disorder.

Researchers looked at 842 children and young adults with Down syndrome who visited the Boston Children’s Hospital Down Syndrome Program between March 2018 and March 2023 to evaluate how they tracked developmentally.

The findings, published online this week in the journal Pediatrics, show striking differences when compared to their typically developing peers.

Most kids with the chromosomal disorder are able to walk independently in their home by age 4½, follow one-step directions by age 5½, run and use stairs by around age 8 and drink from an open cup by about 12. It’s not until the teen years that at least 75% of children with Down syndrome can follow two-step directions or use at least 50 words, signs or pictures.

All of these are skills that the Centers for Disease Control and Prevention indicates that most kids pick up by age 2½, the study notes.

“The American Academy of Pediatrics recommends that children and adolescents with Down syndrome receive anticipatory guidance regarding development and behavior. However, few tools provide specific guidance on developmental norms for children with Down syndrome,” wrote Dr. Nicole Baumer and her colleagues from Harvard University in the paper. “Our objective was to estimate age ranges at which children and adolescents with Down syndrome achieve developmental milestones to facilitate developmental screening by pediatric practitioners.”

The study involved individuals with Down syndrome ages 2 months to 24 years and relied on data collected from caregivers, physical therapists and through electronic health records. Researchers assessed the likelihood of achieving 25 different developmental milestones.

In a commentary published in Pediatrics alongside the study, Dr. Marilyn Bull of the Indiana University School of Medicine said the findings will help clinicians determine if developmental delays are typical or merit further evaluation. The research is also notable, Bull said, for offering insights on what to expect into early adulthood.

“Currently developmental assessment is based predominantly on clinical expertise but now clinicians will be able to systematically assess development in several domains at routine health supervision visits,” Bull wrote. “These data illustrate that achievement of skills is spread over a wider age span in persons with Down syndrome than neurotypical children and that it can be used by clinicians to effectively evaluate developmental progress.”