The CDC changed its milestone charts. What should parents do with them?

There is a difference between asking when babies usually learn something and asking when a doctor should look more closely at a baby who hasn't learned it yet. A milestone chart has to put an age next to a skill, so it can look as though those two questions have the same answer.

Then the chart changes, and suddenly something that seemed late yesterday appears to be on time today.

This is part of what made the CDC's 2022 milestone revision so confusing. Some skills moved to later ages, which sounds like lowering the expectations for babies. But to understand what happened, you have to look at what the age on that particular chart was supposed to do in the first place. Otherwise, a number meant to help a parent get assistance can become a reason they're told to wait.

What does “most babies” actually mean?

Say you're looking at the age when half of children have acquired a skill. That gives you an idea of when it starts becoming common, but it also means the other half haven't done it yet. A baby missing that skill is in quite a large group. Looking at that fact alone doesn't tell a clinician much about which child needs a closer look.

The revised CDC checklists aimed to place milestones at an age when at least 75% of children would be expected to have them. The intention was to make a missing skill harder to dismiss with “let's wait and see,” because it would now be a skill a larger majority already had. How the CDC selected the revised milestones

So, yes, some ages changed. Of the retained milestones that moved to a different age, 67.7% moved later. That statistic is about edits to the checklist. It is not a finding that two-thirds of babies are failing, or that children as a population have started developing more slowly.

But there is a problem you can already see here. The chart is trying to make an absent skill a clearer reason to act. A parent may read the same chart as an instruction to hold off until that birthday. Those are very different uses of the same number.

A baby can be working towards a skill for weeks or months before the moment someone ticks the box. If all the attention goes to the date, it's easy to overlook what is happening during that time.

Before the first steps, there is quite a lot to see

Take walking. The current CDC list includes taking a few steps independently at 15 months. At 18 months it includes walking without holding on to a person or an object. Already, “when should my baby walk?” has turned out to contain two different descriptions. The 15-month checklist, the 18-month checklist

On your own floor, you can see more than a yes or no. Perhaps your baby is pulling up more often, moving along the sofa, letting go for a moment and then sitting down. Another parent might be worried because a movement their baby used to make has disappeared. Both could arrive at an appointment asking about walking, but they have different things to explain.

That is why it helps to describe what you have seen, including how it has changed, rather than trying to find the one age that settles the whole question. Our movement milestone guide follows how skills build on each other. You can use it to understand what you're watching without making each attempt an exam.

The CDC itself describes its checklists as communication tools. It says they should not be used to diagnose a delay or to decide whether someone needs to start, continue or stop receiving services. The next step when a concern comes up is screening, evaluation or referral. The checkboxes are supposed to help that process begin. The CDC's instructions for using its checklists

This also means a checklist needs good evidence behind its individual entries. If parents and clinicians are going to use an age to decide what happens next, how was that age chosen?

The language researchers who went back to the references

A group of researchers at Northwestern asked that question about three of the revised vocabulary milestones. They went through the supporting sources and compared the evidence with the numbers of words and ages that had ended up on the page.

One of those entries is about saying approximately 50 words at 30 months. The reviewers found that none of the sources they examined supplied the evidence needed to place that skill as late as 30 months. They also found problems with how well the study samples represented US children, including children learning more than one language. This was a specific criticism of the evidence used to build the checklist, rather than a study following children to see whether the revision had delayed their diagnoses. Roberts and colleagues' review

The 50-word item is still on the current 30-month checklist. That page also tells parents to raise concerns about skills their child has lost or anything else that worries them, and to ask about developmental screening.

So if you're concerned about your child's speech before that age, the number isn't an instruction to keep quiet. Tell the clinician what words your child uses, how they communicate with you and what has changed. Ask what they would want to assess. You don't need to resolve the argument between the researchers and the CDC before you can have that conversation.

What happens after “we'll keep an eye on it”?

This is where a lot of the usefulness of an appointment is decided. You have explained the concern, someone has listened, and perhaps their recommendation is to monitor it for now. Before you leave, find out what that will involve.

What are you looking for? When will you review it together? What would mean calling sooner? If a referral is being made, who will contact whom? Those answers give you something to do with the time between appointments, instead of going home with the same worry and another search tab open.

You can ask plainly.

“I'm still concerned about this. Would a developmental screen help us understand it? If we're going to wait, what should change during that time, and when are we checking again?”

A developmental screen is a more structured check using a formal tool; it helps decide whether an assessment is needed. The ordinary milestone list on your phone is not that check. The CDC explains how monitoring and screening fit together.

If the explanation hasn't addressed what you're seeing, say so. Ask for another opinion if you need one. And if your child has lost a skill, contact their healthcare professional promptly rather than waiting for a later checklist age. What to do when you're concerned

In the US, you can also contact your state or territory's early intervention program directly for a child under three. At three and older, the local public school system can explain its evaluation process. You can request an evaluation without already having a diagnosis or a doctor's referral; the local service then assesses eligibility. How to find an evaluation

Meanwhile, everyday play can continue. If floor time is the difficulty you're trying to work through, the tummy-time guide looks at that immediate problem. Individual guidance from someone who has assessed your baby takes priority over a general exercise suggestion.

A chart can help you notice something you hadn't thought to ask about. What it can't do is make the thing you've already noticed disappear. Bring that observation with you, explain it, and keep going until you understand what the next step is.