Understanding Updated Developmental Milestones

Dr. Paul Lipkin specializes in Neurodevelopmental Disabilities and Developmental and Behavioral Pediatrics at the Kennedy Krieger Institute in Baltimore, where he directs medical outpatient services. He is also a Professor of Pediatrics at the Johns Hopkins School of Medicine. He has focused his academic work on surveillance and screening for developmental and behavior problems, including autism, for nearly two decades through the American Academy of Pediatrics. He also directed the Interactive Autism Network, a family-centered online research registry for autism, from 2013 to 2019. He is the senior author for the newly released developmental milestones and was involved with the project's data collection and analysis.

As we start talking about the new milestones, let’s start with the basics: Why is understanding typical development so vital? Kids all develop at their own pace, so how does clarifying common milestones have value?

Developmental milestones are a tool developed nearly a century ago by early childhood researchers, such as Arnold Gesell, in order to best understand the usual pattern of development of children. Milestones, as we have come to know them, are key skills and the ages when children on average develop them. They are typically observable to a parent or professional and allowed for best documentation of a child’s development.

In their original intent, milestones were created to identify children who were not following a typical pattern and thus might have a problem in development warranting better medical understanding and treatment. With their continued and popular use over time, the milestones have served as an educational tool for parents to learn what to expect as their child ages and grows as well as to gear play and interaction appropriate to a child’s level of skill and understanding.

Photo by Sharon McCutcheon: https://www.pexels.com/photo/assorted-color-bricks-1148496/

Source: Photo by Sharon McCutcheon / Pexels

Since children vary in the age when these skills develop, professionals have tried to use them to identify children whose pattern is slower than typical and possibly suggestive of a specific developmental problem (and related medical problem at times). Published milestone lists sometimes reflect the average age (50th percentile) or sometimes represent ages when most children (75th or 90th percentiles) have developed the skill.

There has never been a consensus as to the best ages to use in monitoring milestones. In addition, the research that created these percentiles has often been old or not rooted in large, representative samples of children. With an accurate set of milestones and a consensus on best ages to publish (based on a specific percentile of children who typically meet that marker of development), we can best identify both typical as well as delayed development in children, with minimal errors (either false positive or false negative predictions).

What are some familiar milestones for parents that have been adjusted in the new update, and why were they changed?

In moving forward from previously published milestones that were based on the 50th percentile (average for age) to now the 75th percentile (most children), many milestones shifted to an older age. For example, understanding “no” was previously published at the 9-month level and now is listed at 12 months, with an expanded description (“pauses briefly or stops when you say it”). “Eats with a spoon” was previously listed at 18 months and is now at 24 months. While some worry that with the newer, later dates some delays may be missed, that shouldn’t be a problem if parents and professional understand that the new ages represent when most (or three-quarters) of children achieve these skills, not half as commonly published before.

This new set up provides better indicators of when parents should be concerned and discuss their concerns with their pediatric or early childhood professional. Also importantly, the initial version of the CDC’s Learn the Signs. Act Early (LTSAE) materials did not include milestones for 15 months and 30 months. The new information includes these ages when children have well-child visits.

Social emotional development was emphasized in this new update. What research is that based on, and what are some new milestones to consider?

With the increased understanding and awareness of autism in early childhood, it has become recognized that children with autism may have delays in social engagement and communication from an early age. Prior milestone lists did not offer many social emotional milestones. We therefore gave extra attention to including markers of social development to aid in the early identification of this developmental condition.

There are unfortunately limited published norms for social milestones, but we sought out publications and measures that include such skills. When further research seemed warranted, the tables indicate this fact. We now have new milestones for the LTSAE materials such as “Laughs” (6 months), “Puts hands out for you to wash them” (18 months), or “Notices other children and joins them to play” (3 years).

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What concerns have people raised about these changes, and how would you respond to them?

Some early childhood professional organizations and their members were concerned with the discrepancy in milestone ages between their materials and publications with those in the paper and the LTSAE materials. Representatives of the authorship group from the CDC met with key organizations for full discussion around their concerns, and statements were released to better inform their membership and the public on the publication and its intended uses.

Many of the discrepancies are rooted in the changes resulting from publishing the milestones for the 75th percentile instead of 50th. There were also concerns with exclusions of some milestones, such as crawling, whose norms have shown discrepancy across measures. And yet, crawling is frequently excluded entirely from guidelines since many children skip this skill without any adverse consequences.

At the same time, with initial press releases about our new publication, conspiratorial thinking and misinformation emerged that suggested the CDC sneaked the information out and was making the milestones later to hide that children were being harmed by the masking used for prevention of COVID-19 infections. Of course, the data for the revisions was gathered from outside publications that predated the pandemic. Work tied to the manuscript also began in 2019 before the pandemic’s onset. Fortunately, these myths were quickly dismissed by outside reviewers of the publication and the materials, and by journalists too.

Early intervention is so valuable in catching up children who are struggling, yet evaluations often get delayed for various reasons. But it seems like early childhood interventions are typically nonmedical and educational in nature. They don’t have much downside when implemented well. How would you summarize, overall, the benefit of getting started early when kids fall behind developmentally?

An early childhood developmental intervention aims to promote the development of new skills, both in areas of delay as well as in areas of strengths. In doing so, early intervention teachers and therapists become supportive guides for a parent around their child’s development, showing them skills to promote and enabling a child and family to develop stronger relationships around development and learning. And quite importantly, early intervention has been shown to benefit children as well as families across many different areas of development.