Developmental Milestones and Red Flags: Birth to Three
A Complete Guide for Parents, Caregivers & Therapists
Dr. Eva Lassey, PT, DPT reviewed the motor development and therapy content in this article. Communication and social milestones follow published guidance from the CDC and the American Academy of Pediatrics. How we write and who reviews it
Developmental milestones describe what most children can do by a given age across four areas: movement, thinking, social and emotional development, and communication. They are a guide rather than a schedule, and children vary considerably. What matters more than any single missed milestone is a pattern — several delays together, delays across more than one area, or the loss of a skill a child previously had. If you are concerned, you do not need to wait for a doctor’s referral. In the United States, a parent can contact their state’s early intervention program directly, at no cost, and ask for an evaluation.
Overview
What is Early Childhood Development?
Early childhood development refers to the incredible journey of growth and change a child undergoes from birth to age five. This period is marked by rapid progress in several key areas: physical (gross and fine motor skills), cognitive (thinking and problem-solving), social-emotional (interacting with others and managing feelings), and communication (language). Each skill builds on the last, creating the foundation for all future learning and well-being.
Why Are Developmental Milestones Important?
Developmental milestones are a set of functional skills that most children can do by a certain age. They act as a helpful guide for parents and professionals to gauge a child’s progress. While every child develops at their own pace, these milestones provide a general timeline for healthy development. Spotting delays early allows for timely support, which can make a significant difference.
What is a Developmental Delay?
A developmental delay is when a child does not reach their developmental milestones within the expected age range. It is more than just being a little “late” on one skill. A delay can occur in one or multiple areas, such as motor skills, speech, or social interaction. Early intervention is the most effective way to help a child catch up and build the skills they need to thrive.
What is Early Intervention?
Early Intervention (EI) is a system of services and therapies designed to help babies and toddlers (from birth to age three) who have developmental delays or disabilities. It is a family-centered approach that provides the tools and support needed to address challenges early, taking advantage of the young brain’s incredible capacity for learning and change. Services often include physical, occupational, and speech therapy.
Signs & Symptoms
About the ages on this page. These are general guides, not a test. The CDC revised its developmental milestone checklists in 2022, moving from what half of children can do at a given age to what most can — so ages you have seen elsewhere may differ. Check the current checklists at CDC Learn the Signs. Act Early. Children born prematurely are assessed against their corrected age. A single missed milestone is rarely the concern; a pattern is — several together, delays in more than one area, or a skill that has gone backward.
Milestones and red flags by age
What most children can do by each age, and what is worth asking about if they cannot. Scroll sideways on a small screen.
By this age
Most children can
Worth asking about if not
2 months
Hold their head up during tummy time
Watch you as you move
Smile when you smile or talk to them
Not reacting to loud sounds
Not looking at your face
Not making sounds other than crying
4 months
Hold their head steady without support when you hold them
Push up onto their elbows on their tummy
Coo, and make sounds back when you talk
Head still not steady when held
Not bringing hands to mouth
Not cooing or making sounds back
6 months
Roll from tummy to back
Push up on straight arms on their tummy
Take turns making sounds with you, and laugh
Not rolling from tummy to back
Not pushing up on their arms
Not laughing or making squealing noises
9 months
Sit without support, and get into sitting on their own
Look when you call their name
Babble strings of sounds like “mamamama”
Not sitting without support
Not looking when you call their name
Not babbling
1 year
Pull up to stand, and walk holding on to furniture
Wave “bye-bye”
Call a parent “mama” or “dada”, and understand “no”
Not pulling up to stand
Not waving or using gestures
No “mama”, “dada” or other name for a parent
15 months
Take a few steps on their own
Try one or two words besides “mama” and “dada”
Point to ask for something or to get help
Not taking steps on their own
No words besides “mama” and “dada”
Not pointing to ask for things
18 months
Walk without holding on to anyone or anything
Try three or more words besides “mama” and “dada”
Point to show you something interesting
Not walking independently
Fewer than three words
Not pointing to show you things
2 years
Kick a ball, and run
Say at least two words together, like “more milk”
Use gestures beyond waving and pointing
Not walking steadily or running
No two-word phrases
Not pointing to things in a book when you ask
30 months
Jump off the ground with both feet
Say about 50 words, and use “I”, “me” and “we”
Pretend — feeding a block to a doll as if it were food
Not jumping with both feet
Not putting two words with an action word together
No pretend play
3 years
Talk well enough for others to understand, most of the time
Hold a conversation with two back-and-forth exchanges
Put on some clothes, and use a fork
Speech others usually cannot understand
Not asking “who”, “what”, “where” or “why”
Not joining other children to play
Source: CDC, Learn the Signs. Act Early. — developmental milestone checklists, 2 months to 3 years. Each row checked against the published checklist on August 11, 2026.
A single missed milestone is usually not the concern. What matters is a pattern — several together, delays in more than one area, or a skill that has gone backward.
And this is a guide, not a test. Children born prematurely are assessed against their corrected age. Children vary. Your sense that something is not right is worth more than any checklist.
Causes & Risks
What Causes Developmental Delays?
Developmental delays are symptoms, not diagnoses. They are caused by underlying factors that affect the developing brain and body. Often, the exact cause is unknown, but common risk factors include:
Prematurity & Low Birth Weight: Being born too early is the single largest risk factor for developmental delays.
Genetics: Some conditions that cause delays, like Down syndrome, are genetic.
Birth Complications: A lack of oxygen or trauma during birth can damage the developing brain.
Positional Factors: Issues like Torticollis (tight neck muscles) can create a chain reaction of motor challenges.
Environmental Factors: Extended time in seats, swings and carriers reduces the floor time babies need to build strength and try new movements.
Diagnosis & tests
How Are Developmental Delays Diagnosed?
There is no single test for a developmental delay. The process involves careful monitoring and evaluation over time.
Developmental Monitoring & Screening: Your pediatrician tracks your child’s milestones at well-child visits. If concerns arise, they will use a formal screening tool to get a clearer picture.
Referral for Evaluation: If the screening shows a delay, your child will be referred for a comprehensive evaluation by a specialist, such as a pediatric physical therapist (PT), occupational therapist (OT), or speech-language pathologist (SLP).
Comprehensive Assessment: Therapists use play-based, standardized tests to pinpoint your child’s specific strengths and challenges, leading to a diagnosis and treatment plan.
Three ways to get an evaluation
Most parents know about one of them.
Under three — early intervention. Free, no income test, no diagnosis needed, and you can refer your own child. Search “[your state] early intervention.” This is the fastest route and the one most parents do not know exists.
Three and over — your school district. Request an evaluation in writing, which starts a legal timeline. See IEPs and 504 plans.
What to bring to any evaluation: specific examples with dates where you have them, videos of what you are describing, a note of anything that has changed, and what you have already tried.
The Importance of Trusting Your Gut
You know your child best. If you feel something is not right with your child’s development, speak up. You do not need a doctor’s referral for early intervention. In the US a parent can contact their state’s program directly — it is free, there is no income requirement, and you can call today. Search “[your state] early intervention.” You can also ask your doctor for a referral to a pediatric therapist, but you do not have to wait for one to get started. Acting on your concerns is the most important first step.
Care & treatment
How Are Developmental Delays Treated?
The primary treatment for developmental delays is pediatric therapy, and early intervention is key. The goal is to build the foundational skills a child needs to progress and participate fully in daily life.
Physical Therapy (PT): Helps with gross motor skills like sitting, crawling, and walking, as well as balance and strength.
Occupational Therapy (OT): Helps with fine motor skills, daily activities (feeding, dressing), sensory processing, and play.
Speech-Language Therapy (SLP): Helps with communication, language understanding, speech clarity, and feeding/swallowing skills.
The Role of the Family
Therapy is most effective when it becomes part of your daily life. Therapists act as coaches, empowering you with strategies and activities to practice at home. Your active participation is the most critical factor in your child’s success.
Living With
How Can Parents Support Their Child's Development at Home?
Your home is your child’s primary learning environment. Simple, intentional choices can make a huge impact on their development.
Prioritize Floor Time: The floor is the best place for a baby to build strength and learn to move. Limit time in “containers” like swings and seats that restrict movement.
Make Tummy Time Fun: Tummy time is the foundation for all motor skills. Get on the floor with your baby and use toys and mirrors to make it engaging.
Narrate Your Day: Talk, sing, and read to your baby constantly. This builds the foundation for language long before they can speak.
Be a Play Partner: Get down on your child’s level and engage with them. Follow their lead and be a responsive, encouraging presence in their exploration.
Finding Your Support System
Connecting with other parents who have children with similar challenges can be an invaluable source of emotional support and practical advice. Ask your therapy team about local or online parent groups. Remember to take care of yourself so you can be the best advocate for your child.
Start Here: Not sure where your concern fits? Routing by symptom, across all ages.
Global Developmental Delay: What the term means when delays appear in more than one area, and why it is provisional.
Therapy by Age: What physical, occupational, and speech therapy actually look like at each stage.
Choosing Your Pediatric Therapy Team: A guide to finding the right physical, occupational, and speech therapists who will partner with you on your child’s journey.
When should I worry about my baby not rolling or sitting?
Most babies roll from tummy to back by around 6 months and sit without support by around 9 months. A single milestone slightly late is usually not a concern. Not rolling by 6 months, or not sitting without support by 9 months, is worth asking about.
My baby is not talking yet. When should I be concerned?
Most children call a parent “mama” or “dada” by around 12 months, try one or two other words by 15 months, and three or more by 18 months. Not looking when you call their name by 9 months, not using gestures such as waving or pointing by 12 months, or having no words besides “mama” and “dada” by 18 months are all worth raising.
Do I need a doctor’s referral for early intervention?
No. In the United States, a parent can contact their state’s early intervention program directly. It is free, there is no income requirement, and you do not need a diagnosis. Search “[your state] early intervention.”
My child lost a skill they used to have. Is that normal?
No, and it is the one thing worth acting on immediately. Loss of a previously acquired skill is investigated differently from being slow to gain one, and it warrants prompt medical evaluation rather than watchful waiting.
What causes developmental delays in children?
Often the cause is not identified. Known risk factors include prematurity and low birth weight, some genetic conditions, birth complications, and positional factors such as torticollis. A delay is a description rather than a diagnosis — the question is what is underneath it.
My baby was born premature. Should I use their actual age?
Generally no. Babies born prematurely are usually assessed against their corrected age, adjusting for how early they arrived. Your pediatrician can tell you how long that adjustment applies.
Will my child catch up on their own?
Some children do. But waiting to find out costs time in the period when support is most effective, and under three an evaluation is free. There is little downside to asking early.
What actually happens in early intervention?
First an evaluation. Then, if your child qualifies, services delivered mostly in your home and built around your daily routines. Therapists coach you as much as they work directly with your child.
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