If you are a parent, you have likely played the “Comparison Game.”
You are at a playgroup. You look over and see another baby—the same age as yours—sitting up perfectly straight while yours is still wobbly. Or maybe your cousin’s toddler is speaking full sentences, while yours is still happily babbling “ba-ba-ba.”
A knot forms in your stomach. Is something wrong? Is my child falling behind?
As a doctor, I see this anxiety daily. Parents come in with growth charts they found online and checklists of milestones, terrified that their child has missed a deadline.
Here is the truth: Children do not read rulebooks. Development is not a race; it is a window. However, there are specific signals—we call them “Red Flags”—that tell us when we need to intervene.
Here is my guide to navigating growth, milestones, and the anxiety that comes with them.
1. The “Milestone Window”
Average is not a deadline.
When you read that “babies walk at 12 months,” that is an average. That means 50% of babies will walk before that, and 50% will walk after.
In medicine, we look at Windows of Achievement. The window for walking is actually anywhere from 10 months to 18 months. A child walking at 11 months and a child walking at 17 months are both considered developmentally normal.
Common “Normal” Ranges:
- Smiling: 3 weeks to 8 weeks.
- Sitting: 4 months to 9 months.
- First Word: 8 months to 14 months.
Key Takeaway: Just because your child is at the later end of the window does not mean they are delayed. They might just be focusing on a different skill right now (e.g., focusing on talking instead of walking).
2. The Percentile Trap
Bigger is not always better.
Many parents believe that being in the 90th percentile for weight is an “A+” grade, and being in the 10th percentile is a failure. This is false.
Percentiles are just statistical measures of size, not health. A child in the 5th percentile can be perfectly healthy, just petite (especially if the parents are petite!).
What Doctors Actually Look For:
We look for Consistency (The Curve).
- Good: A child who stays steadily on the 15th percentile line from birth to age 2. They are growing at their own consistent rate.
- Concern: A child who drops from the 75th percentile suddenly down to the 25th. That is “crossing centiles,” and it tells us growth has stalled.
3. When to Worry (Red Flags)
The “Limit Ages”
While there is a wide range of normal, there are “Limit Ages.” These are the absolute deadlines set by guidelines (like NICE in the UK) where, if a child hasn’t reached a milestone, we need to investigate.
See a doctor if your child is NOT:
- By 8-10 Weeks: Smiling at you.
- By 12 Months: Sitting unsupported.
- By 18 Months: Walking independently.
- By 2 Years: Putting two words together (“More milk”).
🚨 The Ultimate Red Flag: Regression
If your child had a skill (e.g., could wave bye-bye, could say 3 words) and then lost it, you should see a doctor immediately. Regression is never considered normal development.
Check Your Child’s Progress
Use our free interactive tool
I built a tool based on the NICE guidelines that calculates your child’s exact age and gives you a specific checklist for their development stage.
Final Thoughts
Developmental delay is not a failure of parenting. It is simply a signal that a child needs extra support. The earlier we catch it, the better the outcome.
Trust your parental instinct. If you feel something is wrong, get it checked.
