Developmental Red Flags by Age: When to Worry & What to Do
Every parent wonders at some point: is my child on track? The truth is that children develop on a wide, healthy range of timelines — but there are specific signs that are worth acting on early rather than "waiting to see." This guide lays out the developmental red flags from 6 months to 3 years, explains what's normal variation versus a real concern, and tells you exactly what to do if something feels off. Acting early is never wasted: it either brings peace of mind or unlocks support during the years it matters most.
The one sign to never ignore — at any age
Loss of skills. If your child stops doing something they used to do — using words, gestures, social smiles, or eye contact — contact your pediatrician right away, regardless of age. Developmental regression is the most important red flag of all.
Red flags by age
Your child doesn't need to show every sign for an evaluation to be worthwhile. Patterns matter more than any single behavior, and "not yet" close to an age is different from a clear, persistent gap.
By 6 months
- Doesn't smile socially or show joy around familiar people
- Doesn't make eye contact or follow objects with their eyes
- Doesn't respond to sounds or voices
- Seems very stiff or very floppy, or has trouble holding their head up
By 9 months
- Doesn't babble or make a variety of sounds
- Doesn't respond to their own name
- Doesn't sit with support, or doesn't bear weight on legs when held
- Shows no back-and-forth sharing of sounds, smiles, or expressions
By 12 months
- Isn't using gestures like pointing, waving, or reaching to be picked up
- Isn't babbling strings of sounds or saying any words
- Doesn't search for objects they see you hide
- Doesn't pull to stand or move to get a toy
By 18 months
- Isn't saying any single words
- Doesn't point to show you interesting things (sharing attention)
- Isn't walking
- Doesn't copy others or engage in simple pretend play
By 24 months (2 years)
- Isn't using two-word phrases ("more milk", "want up")
- Doesn't follow simple instructions
- Doesn't imitate actions and words
- Can't walk steadily, or walks only on toes consistently
By 36 months (3 years)
- Speech is hard for familiar adults to understand
- Doesn't speak in short sentences
- Has little interest in other children or pretend play
- Has frequent trouble with stairs, balance, or coordination
Want the full, positive checklist of what most children do at each age? See our detailed milestone pages, including 9 months, 18 months, 2 years, and 3 years — or check your child's milestones with our free tool.
Red flag vs. normal variation
It's easy to spiral when comparing your child to others. Keep this in mind: a child who is a few weeks behind a milestone, who is simply shy or cautious, or who skips crawling and goes straight to walking is usually developing just fine. Red flags are about clear, persistent gaps, several signs appearing together, or loss of skills — not small differences in timing. When you're unsure, an evaluation settles the question without any downside.
What to do if you notice red flags
- Write down what you're seeing (and when skills appeared or disappeared). Your observations are the most valuable information a specialist has.
- Talk to your pediatrician and share your notes specifically.
- Request a free Early Intervention evaluation. You don't need a referral or a diagnosis — you can ask yourself. It's free in every U.S. state for children under 3.
Not sure how the evaluation works? Read our guide on what a free Early Intervention evaluation actually looks like. You can also explore related topics like speech delay, early signs of autism, and motor skills.
Trust your instincts — and act early
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Start your free action plan →Frequently asked questions
What are developmental red flags?
Developmental red flags are signs that a child may not be developing typically for their age — like not babbling by 12 months, not walking by 18 months, or losing skills they once had. They are reasons to check in with your pediatrician, not a diagnosis.
When should I worry about my child's development?
Trust your instincts. Worth acting on promptly: losing skills at any age, not responding to their name by 12 months, no words by 16 months, no two-word phrases by 24 months, or not walking by 18 months. When several signs appear together, ask for an evaluation.
Is it normal for children to develop at different rates?
Yes. There is a wide, healthy range for when children reach milestones. Red flags are about clear, persistent gaps or loss of skills — not about being a few weeks behind a chart.
What should I do if I notice a red flag?
Talk to your pediatrician and request a free Early Intervention evaluation. You never need a referral or a diagnosis to ask for one, and Early Intervention is free in every U.S. state for children under 3.
What is the most serious red flag?
Losing skills a child once had — such as words, gestures, or social smiles — is the single most important sign to act on right away, at any age.
Sources: U.S. Centers for Disease Control and Prevention (CDC), "Learn the Signs. Act Early."; American Academy of Pediatrics (AAP). EarlyBegin helps you know what to do next — it does not provide medical advice or diagnose. If you have concerns about your child's development, talk to your pediatrician.