Is My Baby Behind? 5 Things a Pediatric PT Looks at Besides Milestone Ages
Updated: Oct 16
If you’ve ever Googled “Is my baby behind?”, you’ve probably found a lot of milestone charts.
Rolling by this age. Sitting by this age. Crawling by this age. Walking by this age.
Those ages can be helpful. But as a pediatric physical therapist, when your baby reaches a milestone is only one piece of the developmental picture.
I also want to know how your baby moves, how comfortable movement seems, and what has changed over time.
A baby might check the “rolling” box while consistently moving over only one side. Another baby might not be moving across the room yet but be showing new ways to reach, turn, and change positions.
Those details help me decide what deserves a closer look.
This doesn’t mean milestone ages don’t matter. The CDC’s milestones describe skills that at least 75% of children can do by a particular age. They help families recognize when to raise a concern, but they do not replace developmental screening or an individualized evaluation. [1]
Think of milestone ages as the beginning of the conversation. These five things help fill in the rest.
1. Symmetry: Is Your Baby Using Both Sides?
Babies are allowed to have preferences. They’re humans, not little robots.
Learning to roll over one side before the other does not automatically mean something is wrong. What catches my attention is a strong preference that keeps showing up.
For example, does your baby:
Almost always look in one direction?
Consistently roll over the same side?
Reach much more often with one hand?
Move one side differently when crawling?
Frequently lean toward the same side while sitting?
I’m interested in both what your baby prefers to do and what they appear able to do.
If a toy catches their attention on the other side, can they comfortably turn toward it? Can they reach with either hand? Does one side seem much harder to use?
A persistent head tilt or turning preference can be associated with torticollis, which may involve tightness in a neck muscle. Other causes are possible, too, so a consistent head position deserves an assessment rather than an assumption. [3]
This is also where a milestone checklist can miss part of the story. A checklist might ask:
“Is your baby rolling?” And the answer might be yes.
But I also want to know how they get there. How are they rolling? Can they roll in both directions? Can they initiate the movement from either side? Does the movement look relatively comfortable?
You do not need to count every reach or make your baby perform the same skill repeatedly. Bring up a difference you keep noticing during ordinary play and care.
The goal is to understand a consistent pattern, not to expect perfectly matching movements.
2. Variety: Does Your Baby Have Options?
I love seeing babies experiment with movement.
They reach for something, shift their weight, wobble, change direction, and try again. Sometimes their solution looks wonderfully inefficient.
That experimentation gives me useful information.
Depending on their age and current skills, I might watch whether a baby can:
Reach for toys in different directions.
Turn their body to follow something interesting.
Shift weight onto one arm while using the other.
Try more than one way to move toward a toy.
Begin moving into and out of positions.
Being able to stay in a position and being able to get there are different skills. For example, the CDC’s 9-month checklist includes both sitting without support and independently getting into sitting. [1]
That distinction matters during an evaluation. If a baby can sit when placed but needs help every time they want to leave that position, I want to understand what makes that transition difficult.
I’m also interested in movement that doesn’t seem to accomplish anything.
Research involving 15-month-old walkers found that much of their walking was exploratory rather than directed toward a particular destination. They moved even when there were no toys in the room. That study involved walking infants, but it offers a useful reminder: movement itself can be part of exploration. Every trip does not need a purpose we can identify. [4]
Babies also use different ways to get around. Some belly crawl or scoot before, or instead of, crawling on hands and knees. The American Academy of Pediatrics emphasizes looking at how both sides participate and discussing concerns about movement with the pediatrician. [5]
I’m not looking for a baby who performs every movement perfectly. I’m looking at the options available to them and whether those options are growing.
“Can they do it?” is useful. “How else can they do it?” can tell us even more.
3. Progress: Compare Your Baby to Your Baby
This may be one of the most important mindset shifts for parents.
Imagine you're at a playgroup and your friend's 8-month-old is crawling everywhere. Your baby is also 8 months old and isn’t crawling. It is incredibly easy to start comparing.
One helpful question is: What was my baby doing a few weeks ago?
Maybe they previously needed help keeping their arms underneath them during tummy time, and now they can support themselves for longer.
Maybe they’re reaching farther without immediately losing their balance.
Maybe they’re turning toward a toy, pivoting on their belly, or beginning to pull their knees underneath them.
Maybe they’re desperately trying to move forward and somehow ending up farther backward.
Those changes are worth noticing. The AAP describes backward movement as something babies may do while learning how to move forward. [5]
Progress can involve more than adding a brand-new skill. In an evaluation, I might also ask whether a familiar movement is becoming easier, whether your baby needs less help, or whether they can use a skill in more situations.
For example, “She can sit” gives me some information.
“She can now sit while holding a toy, turn toward me, and reach without needing me to steady her every time” gives me a much fuller picture.
Milestone anxiety can take a lot of the fun out of watching development happen. Sometimes stepping back and looking at the changes that have occurred over several weeks tells us much more than comparing two babies on the same day.
There is one important limit to comparing your baby with their earlier self: making progress does not automatically rule out a delay or another concern. If a milestone is missing, or something about movement worries you, discuss it with your child’s provider even if other skills are improving. [1,8]
Bottom line: your friend's baby isn't my baseline for your baby.
Your baby is. Compare your baby to your baby.
4. Effort: How Hard Does Your Baby Have to Work to Move?
Some babies are incredibly motivated. Some are cautious. And some babies seem perfectly happy sitting in one spot supervising the entire household. Personality is part of the picture. So is how demanding movement appears to be.
A new skill takes effort. I’m more interested in whether everyday movement consistently seems unusually difficult for that baby’s age and stage
I might ask:
Does your baby seem comfortable supporting their head and body?
Do they repeatedly lose their position almost as soon as they try?
Does one particular movement or position seem uncomfortable?
Do they need a great deal of help to participate in play?
Are familiar movements becoming easier with practice?
The AAP identifies difficulty controlling the head and neck, unusual stiffness or floppiness, and difficulty with skills such as rolling or sitting as reasons to discuss development with a pediatrician. These observations do not tell us the cause by themselves. [2]
This is where an evaluation can be useful. A PT can consider strength, flexibility, balance, coordination, and how those pieces work together during movement.
For example, two babies might both dislike tummy time. One may be learning to tolerate the position while gradually lifting their head for longer. Another may struggle to turn their head or support themselves through their arms. The parent’s description of “hates tummy time” might be the same, but the next steps could be different.
Tummy time offers opportunities to strengthen the neck, shoulders, and arms. It should happen while your baby is awake and supervised, with your baby placed on their back for sleep. [7]
The goal is not to push through distress to achieve a certain number on a timer. If a position consistently feels difficult, ask for help making it manageable.
I want to understand what movement costs your baby, as well as what they can accomplish.
5. When I Don't Love “Let's Just Wait and See”
There are absolutely situations where giving a baby some additional time is reasonable. But I prefer that decision to come with a clear explanation and a plan.
What are we watching for? What changes would we hope to see? When will we check again? What should prompt an earlier call?
That gives parents something more useful than an open-ended “don’t worry.”
One situation that deserves particular attention is losing a skill your baby previously used consistently. Contact their pediatrician promptly if that happens. The CDC recommends acting when a child loses skills, misses milestones, or has other developmental concerns. [1]
A baby choosing not to demonstrate something during one play session is different from appearing unable to do a previously established skill. If you’re unsure which you’re seeing, describe the change to your provider rather than trying to resolve it alone.
Other reasons I may recommend checking in include persistent differences between sides, movement that repeatedly seems difficult, or very little change in the skills we’re watching.
These are reasons to check in, not proof of a diagnosis.
Sometimes an assessment leads to practical suggestions and a plan to review progress. Sometimes therapy is helpful. Sometimes the findings point toward further medical evaluation.
You also do not have to wait for a scheduled screening age to raise a concern. Developmental screening can happen whenever a parent or healthcare provider has a concern. [8]
Asking for an evaluation does not mean you’ve decided something is wrong. It means you would like better information.
What Should You Do If You're Worried About Your Baby's Development?
You don't need to diagnose your baby yourself. But there are a few things you can do that can make a conversation with your child's healthcare provider much more useful.
1. Take a video.
If you're noticing a movement that seems unusual, record it. Babies have an incredible ability to suddenly stop doing the exact thing you're concerned about the moment you walk into a doctor's office.
2. Bring it up.
Talk with your pediatrician about what you're seeing. You can also ask whether a developmental or physical therapy evaluation would be appropriate. An evaluation isn't a diagnosis. Sometimes the most valuable outcome is simply getting reassurance and knowing what to watch next.
3. Describe patterns.
“He seems behind” is understandable. “He reaches with his right hand almost every time, even when I offer a toy on his left” gives your provider something specific to explore.
4. Explain what has changed.
Mention when you first noticed the pattern, whether it happens repeatedly, and whether it is improving or becoming more difficult.
5. Ask for a next step.
You might say, “Would developmental screening or a pediatric PT evaluation help us understand this?” Parent observations are an important part of assessing development. [2]
For children under 3 in the United States, families can also contact their state’s Early Intervention program directly to request an assessment. Eligibility and services depend on the program and the child’s needs. [8]
Milestones Are Guidelines, Not Grades
Milestone ages matter. They give parents and healthcare professionals useful developmental information.
But milestones aren't a report card for your baby. And they're definitely not a report card for you as a parent.
Alongside “When did my baby do it?”, ask:
How is my baby doing it?
Are both sides participating?
What new options are appearing?
Is movement becoming easier?
Is there anything we should understand more clearly?
You are allowed to enjoy your baby’s development and ask questions about it at the same time.
You don’t need to choose between worrying about everything and dismissing your concerns. You can notice a pattern, ask for guidance, and get a clearer sense of what comes next.
Want More Practical Baby & Toddler Development Information?
Watch the full video that goes with this article, and follow Dr. Cyndi on YouTube, Facebook, and Instagram for more pediatric physical therapy and developmental education.
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Have a topic you'd like me to cover next? Rolling, sitting, crawling, walking, low muscle tone, feet and shoes? Send it my way. If you're Googling it late at night, there's a good chance another parent is wondering about it too.
Free Parent Resource
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Download the Starting Point Infant & Toddler Motor Milestone Guide: Birth to Walking for an overview of emerging movement skills, signs to discuss with your child’s provider, and ways to support development through everyday play.
References
Centers for Disease Control and Prevention. Milestones by 9 Months. Includes an explanation of CDC milestones and guidance on developmental concerns.
American Academy of Pediatrics. Is Your Baby’s Physical Development on Track?
American Academy of Pediatrics. Head Tilt (Torticollis).
Hoch JE, O’Grady SM, Adolph KE. It’s the Journey, Not the Destination: Locomotor Exploration in Infants. Developmental Science. 2019;22(2):e12740.
American Academy of Pediatrics. Movement Milestones in Babies 8 to 12 Months Old.
American Academy of Pediatrics. Corrected Age for Preemies.
Eunice Kennedy Shriver National Institute of Child Health and Human Development. Benefits of Tummy Time.
Centers for Disease Control and Prevention. Developmental Monitoring and Screening.
Educational Disclaimer
This article is for general educational purposes only and is not intended to diagnose or treat any child or replace individualized medical or physical therapy advice. Reading this information does not establish a physical therapist-patient relationship. If you have concerns about your child's development, discuss them with your child's pediatrician or an appropriately licensed healthcare professional.
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