Emily Oster

8 min Read Emily Oster

Emily Oster

New Developmental Milestones from the CDC

What changed and why

Emily Oster

8 min Read

Developmental milestones hold a certain combination of joy and fear for parents. On one hand, we look forward eagerly to the first smile, the first step, the first word. On the other hand, milestones are an opportunity to fear that our children are behind, that they aren’t measuring up. When the book says “the average age for walking is 12 months” and our 15-month-old is still crawling around, it can be a source of stress (I speak to this one from experience).

With this context, it wasn’t surprising when people sat up and took notice of the recent CDC update to developmental milestones. It was the first time in many years that the agency has updated these. One change was to include additional sets of milestones at 15 and 30 months. A second was to, generally, make the milestones “easier” — to lower the expectations around things like language development.

This newsletter will do three things: First, explain why the CDC made these changes. Second, talk about the new guidelines around language in particular. And third, take a look at some broader data on language development, which gives more of a sense of the distribution.

Why the change?

I have seen some suggestions online that the change in guidelines is reflecting the fact that children are developing more slowly, and that the CDC is trying to hide this. In a few cases, the narrative surrounds the role of masks (lately, I feel like it always comes back to masks). These claims are untrue.

The guidelines seem to have been changed with the goal of making it easier to identify children who are eligible for early intervention. Early intervention refers to a suite of services available to children with developmental delays or disabilities. Children are identified as potentially eligible for these services by a pediatrician, a social worker, or child-care personnel.

Early-intervention programs can help children catch up to their peers. Given that, identifying eligible children is a high priority. Which means we want to make it easy to do. The goal of having developmental milestones is to do just this — to have a simple way to flag a child as possibly needing some help. But to do that, the milestones need to be organized to identify children in this group rather than to (say) identify the average child.

The last round of developmental milestones from the CDC focused more on what we would expect from the average child. This update is intended to capture something like: at least 75% of children at this age would meet this milestone. This means, then, that if a child is not meeting it, they are in the lower 25% in terms of that area. And this is the group we want to flag for possible early intervention. Prior to the update, the guidelines were closer to identifying the average — the 50th percentile. But, of course, moving from a milestone that identifies the 50th percentile of the distribution to one that identifies the 25th percentile will change the expectation.

All that is to say that much of the reason for the change (as I understand it) was to enhance the usefulness of the guidelines for pediatricians. It is unrelated to masking, and doesn’t reflect any systematic change in realized child development.

The guidelines on language

That’s the background. With that, I wanted to dive into the guidelines on language in particular, because they got a big update. (Another big update was to drop crawling as a milestone. This is a source of debate, as it is not uncommon for kids to skip crawling altogether, but there are those who think it’s an important milestone to identifying possible issues. I’m going to leave this for another day.)

You can see the full CDC guidelines here, but I’ve pulled out the “productive” language and gesture guidelines at each age group in the table below.

Again, these milestones are intended to represent levels of concern, not averages. The median child (more on this below) does say several words by one year of age. But: at 12 months, there isn’t a flag for concern unless we do not see the use of a caregiver word.

One thing that this table makes clear is the relatively slow increase in language up to 18 months, and then the explosion after. In moving from 24 months to 36 months — that’s two to three years — the expectation for what most children can do moves from putting two words together to “talks well enough for others to understand, most of the time.”

This large change is a big part of the reason that the new guidelines included the 30-month check-in. This has, however, been a source of significant debate. For one thing, counting words is perhaps helpful when we are talking about a small number, but it’s hard to know if a child has 40 or 50 or 60 words. Additionally, commenters have suggested that this milestone is too conservative — that it will miss many children who actually would benefit from additional intervention.

On reflection, I thought it might be interesting to return to the data I explored in Cribsheet. So let’s look at that, and then circle back to the 30-month question.

Word distribution

(Note: A longer discussion of this topic was in the newsletter in August 2020.)

Part of the issue with “50 words” is that it’s hard to count words when you get above a small number. If we want to get a sense of the full distribution of language across the population at various ages, it’s necessary to approach it more systematically.

A standardized approach is to identify a target word set — a compilation of common words — and collect data on the number of these words that children know. It’s possible to then look at the distribution across age in how many words children know. The most popular word list is from the MacArthur-Bates Communicative Development Inventories (MB-CDIs). It has a list of simple words — blanket, kitty, uh-oh — and asks parents if their child understands the word and if they can say it.

These forms are commonly used by many researchers in child development, and there’s a project at Stanford University called Wordbank that compiles a significant body of the data on this. You can visit the project here and produce neat graphs like the one below, on the size of vocabulary by age. It’s possible to divide these by gender or parental education and to look across languages (versions of this inventory appear in virtually all languages).

Even cooler, from a pure parental navel-gazing perspective, the Wordbank also allows you to analyze the data by word. It produces graphs like the one below, from which we learn that a word like windy appears, on average, later than moo or baa baa.

The data on this site is interesting and fun. You can do the inventory yourself if you are so inclined.

Based on these data, we might imagine evaluating the “50 words at 30 months” milestone. One significant caveat, though, is that much of this data comes from research samples that are likely to be selected in various ways. They’re not what is called a “norming sample,” which is what the CDC ideally uses to generate its guidelines. On average, the kids in the Wordbank are differently selected.

However: looking at that first graph above, it does seem like the 50 words at 30 months could be a bit too conservative. In the Wordbank data, even the 10th percentile of children have considerably larger vocabularies. This is true even if we limit the Wordbank data to norming samples, which have a less serious selection problem. To be clear: I do not think there is anything nefarious here, or anything masking-related; just perhaps this particular milestone isn’t quite correctly calibrated.

Final thought

Asking ourselves how our kids measure up — to milestones, to other kids, etc. — is a natural parenting instinct. We tend to regard early achievement of milestones as a sign that our children may, in fact, be wizards.

These CDC milestones are not focused on identifying wizards. They are very sensibly focused on helping find children who might benefit from additional scaffolding and public services. There is a wide range of normal development, and, by and large, the exact speed of development in these areas has relatively little predictive power for long-term outcomes. So by all means, explore the Wordbank database to find out whether the word hat is generally learned before the word tired. But don’t overthink it.

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Milestones. We celebrate them in pregnancy, in parenting, and they’re a fun thing to celebrate at work too. Just a couple years ago I couldn’t have foreseen what this community would grow into. Today, there are over 400,000 of you here—asking questions, making others feel seen wherever they may be in their journey, and sharing information that supports data > panic. 

It has been a busy summer for the team at ParentData. I’d love to take a moment here to celebrate the 400k milestone. As I’ve said before, it’s more important than ever to put good data in the hands of parents. 

Share this post with a friend who could use a little more data, and a little less parenting overwhelm. 

📷 Me and my oldest, collaborating on “Expecting Better”

Milestones. We celebrate them in pregnancy, in parenting, and they’re a fun thing to celebrate at work too. Just a couple years ago I couldn’t have foreseen what this community would grow into. Today, there are over 400,000 of you here—asking questions, making others feel seen wherever they may be in their journey, and sharing information that supports data > panic.

It has been a busy summer for the team at ParentData. I’d love to take a moment here to celebrate the 400k milestone. As I’ve said before, it’s more important than ever to put good data in the hands of parents.

Share this post with a friend who could use a little more data, and a little less parenting overwhelm.

📷 Me and my oldest, collaborating on “Expecting Better”
...

I spend a lot of time talking people down after they read the latest panic headline. In most cases, these articles create an unnecessary amount of stress around pregnancy and parenting. This is my pro tip for understanding whether the risk presented is something you should really be worrying about.

Comment “link” for an article with other tools to help you navigate risk and uncertainty.

#emilyoster #parentdata #riskmanagement #parentstruggles #parentingstruggles

I spend a lot of time talking people down after they read the latest panic headline. In most cases, these articles create an unnecessary amount of stress around pregnancy and parenting. This is my pro tip for understanding whether the risk presented is something you should really be worrying about.

Comment “link” for an article with other tools to help you navigate risk and uncertainty.

#emilyoster #parentdata #riskmanagement #parentstruggles #parentingstruggles
...

Here’s why I think you don’t have to throw away your baby bottles.

Here’s why I think you don’t have to throw away your baby bottles. ...

Drop your toddlers favorite thing right now in the comments—then grab some popcorn.

Original thread source: Reddit @croc_docs

Drop your toddlers favorite thing right now in the comments—then grab some popcorn.

Original thread source: Reddit @croc_docs
...

Just keep wiping.

Just keep wiping. ...

Dr. Gillian Goddard sums up what she learned from the Hot Flash  S e x  Survey! Here are some key data takeaways:

🌶️ Among respondents, the most common s e x u a l frequency was 1 to 2 times per month, followed closely by 1 to 2 times per week
🌶️ 37% have found their sweet spot and are happy with the frequency of s e x they are having
🌶️ About 64% of respondents were very or somewhat satisfied with the quality of the s e x they are having

Do any of these findings surprise you? Let us know in the comments!

#hotflash #intimacy #midlifepleasure #parentdata #relationships

Dr. Gillian Goddard sums up what she learned from the Hot Flash S e x Survey! Here are some key data takeaways:

🌶️ Among respondents, the most common s e x u a l frequency was 1 to 2 times per month, followed closely by 1 to 2 times per week
🌶️ 37% have found their sweet spot and are happy with the frequency of s e x they are having
🌶️ About 64% of respondents were very or somewhat satisfied with the quality of the s e x they are having

Do any of these findings surprise you? Let us know in the comments!

#hotflash #intimacy #midlifepleasure #parentdata #relationships
...

Should your kid be in a car seat on the plane? The AAP recommends that you put kids under 40 pounds into a car seat on airplanes. However, airlines don’t require car seats.

Here’s what we know from a data standpoint:
✈️ The risk of injury to a child on a plane without a carseat is very small (about 1 in 250,000)
✈️ A JAMA Pediatrics paper estimates about 0.4 child air crash deaths per year might be prevented in the U.S. with car seats 
✈️ Cars are far more dangerous than airplanes! The same JAMA paper suggests that if 5% to 10% of families switched to driving, then we would expect more total deaths as a result of this policy. 

If you want to buy a seat for your lap infant, or bring a car seat for an older child, by all means do so! But the additional protection based on the numbers is extremely small.

#parentdata #emilyoster #flyingwithkids #flyingwithbaby #carseats #carseatsafety

Should your kid be in a car seat on the plane? The AAP recommends that you put kids under 40 pounds into a car seat on airplanes. However, airlines don’t require car seats.

Here’s what we know from a data standpoint:
✈️ The risk of injury to a child on a plane without a carseat is very small (about 1 in 250,000)
✈️ A JAMA Pediatrics paper estimates about 0.4 child air crash deaths per year might be prevented in the U.S. with car seats
✈️ Cars are far more dangerous than airplanes! The same JAMA paper suggests that if 5% to 10% of families switched to driving, then we would expect more total deaths as a result of this policy.

If you want to buy a seat for your lap infant, or bring a car seat for an older child, by all means do so! But the additional protection based on the numbers is extremely small.

#parentdata #emilyoster #flyingwithkids #flyingwithbaby #carseats #carseatsafety
...

SLEEP DATA 💤 PART 2: Let’s talk about naps. Comment “Link” for an article on what we learned about daytime sleep!

The first three months of life are a chaotic combination of irregular napping, many naps, and a few brave or lucky souls who appear to have already arrived at a two-to-three nap schedule. Over the next few months, the naps consolidate to three and then to two. By the 10-to-12-month period, a very large share of kids are napping a consistent two naps per day. Over the period between 12 and 18 months, this shifts toward one nap. And then sometime in the range of 3 to 5 years, naps are dropped. What I think is perhaps most useful about this graph is it gives a lot of color to the average napping ages that we often hear. 

Note: Survey data came from the ParentData audience and users of the Nanit sleep monitor system. Both audiences skew higher-education and higher-income than the average, and mostly have younger children. The final sample is 14,919 children. For more insights on our respondents, read the full article.

SLEEP DATA 💤 PART 2: Let’s talk about naps. Comment “Link” for an article on what we learned about daytime sleep!

The first three months of life are a chaotic combination of irregular napping, many naps, and a few brave or lucky souls who appear to have already arrived at a two-to-three nap schedule. Over the next few months, the naps consolidate to three and then to two. By the 10-to-12-month period, a very large share of kids are napping a consistent two naps per day. Over the period between 12 and 18 months, this shifts toward one nap. And then sometime in the range of 3 to 5 years, naps are dropped. What I think is perhaps most useful about this graph is it gives a lot of color to the average napping ages that we often hear.

Note: Survey data came from the ParentData audience and users of the Nanit sleep monitor system. Both audiences skew higher-education and higher-income than the average, and mostly have younger children. The final sample is 14,919 children. For more insights on our respondents, read the full article.
...

Happy Father’s Day to the Fathers and Father figures in our ParentData community! 

Tag a Dad who this holiday may be tricky for. We’re sending you love. 💛

Happy Father’s Day to the Fathers and Father figures in our ParentData community!

Tag a Dad who this holiday may be tricky for. We’re sending you love. 💛
...

“Whilst googling things like ‘new dad sad’ and ‘why am I crying new dad,’ I came across an article written by a doctor who had trouble connecting with his second child. I read the symptoms and felt an odd sense of relief.” Today we’re bringing back an essay by Kevin Maguire of @newfatherhood about his experience with paternal postpartum depression. We need to demystify these issues in order to change things for the better. Comment “Link” for a DM to read his full essay.

#parentdata #postpartum #postpartumdepression #paternalmentalhealth #newparents #emilyoster

“Whilst googling things like ‘new dad sad’ and ‘why am I crying new dad,’ I came across an article written by a doctor who had trouble connecting with his second child. I read the symptoms and felt an odd sense of relief.” Today we’re bringing back an essay by Kevin Maguire of @newfatherhood about his experience with paternal postpartum depression. We need to demystify these issues in order to change things for the better. Comment “Link” for a DM to read his full essay.

#parentdata #postpartum #postpartumdepression #paternalmentalhealth #newparents #emilyoster
...

What does the data say about children who look more like one parent? Do they also inherit more character traits and mannerisms from that parent? Let’s talk about it 🔎

#emilyoster #parentdata #parentingcommunity #lookslikedaddy #lookslikemommy

What does the data say about children who look more like one parent? Do they also inherit more character traits and mannerisms from that parent? Let’s talk about it 🔎

#emilyoster #parentdata #parentingcommunity #lookslikedaddy #lookslikemommy
...

SLEEP DATA 💤 We asked you all about your kids’ sleep—and got nearly 15,000 survey responses to better understand kids’ sleep patterns. Comment “Link” for an article that breaks down our findings!

This graph shows sleeping location by age. You’ll notice that for the first three months, most kids are in their own sleeping location in a parent’s room. Then, over the first year, this switches toward their own room. As kids age, sharing a room with a sibling becomes more common. 

Head to the newsletter for more and stay tuned for part two next week on naps! 🌙

#parentdata #emilyoster #childsleep #babysleep #parentingcommunity

SLEEP DATA 💤 We asked you all about your kids’ sleep—and got nearly 15,000 survey responses to better understand kids’ sleep patterns. Comment “Link” for an article that breaks down our findings!

This graph shows sleeping location by age. You’ll notice that for the first three months, most kids are in their own sleeping location in a parent’s room. Then, over the first year, this switches toward their own room. As kids age, sharing a room with a sibling becomes more common.

Head to the newsletter for more and stay tuned for part two next week on naps! 🌙

#parentdata #emilyoster #childsleep #babysleep #parentingcommunity
...

Weekends are good for extra cups of ☕️ and listening to podcasts. I asked our team how they pod—most people said on walks or during chores. What about you?

Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster

Weekends are good for extra cups of ☕️ and listening to podcasts. I asked our team how they pod—most people said on walks or during chores. What about you?

Comment “Link” to subscribe to ParentData with Emily Oster, joined by some excellent guests.

#parentdata #parentdatapodcast #parentingpodcast #parentingtips #emilyoster
...

Humility. That’s why. That’s the whole reason.

#emilyoster #secondbaby #parentingjokes #parentinghumor

Humility. That’s why. That’s the whole reason.

#emilyoster #secondbaby #parentingjokes #parentinghumor
...

Bug season is upon us. Besides annoyance, this can bring up safety concerns, particularly with ticks. They are carriers of diseases, most notably Lyme disease. So what’s the best course of action?

Prevention is key! I suggest:
⭐ Regular tick checks
⭐ Using bug sprays with DEET 
⭐ Wearing long sleeves and pants in the woods

Some parents worry about DEET, but repellants with up to 30% DEET are recommended by both the CDC and AAP. The data says you’re in the clear, so go for it. Enjoy your summer!

#parentdata #emilyoster #tickseason #bugbites #bugspray

Bug season is upon us. Besides annoyance, this can bring up safety concerns, particularly with ticks. They are carriers of diseases, most notably Lyme disease. So what’s the best course of action?

Prevention is key! I suggest:
⭐ Regular tick checks
⭐ Using bug sprays with DEET
⭐ Wearing long sleeves and pants in the woods

Some parents worry about DEET, but repellants with up to 30% DEET are recommended by both the CDC and AAP. The data says you’re in the clear, so go for it. Enjoy your summer!

#parentdata #emilyoster #tickseason #bugbites #bugspray
...