In the first two years, babies typically move through a predictable sequence of skills across five areas of development. Every baby has their own pace, and a wide range of timing is normal - but here's a general guide to what's typical and when.
Note: This is general information, not medical advice or a diagnostic tool. Your pediatrician tracks your baby's development at every checkup and is the right person to ask if you have concerns.
The 5 Developmental Domains
- Social: smiling, interacting, showing affection, playing with others
- Language: babbling, understanding words, speaking, following instructions
- Gross motor: big movements - rolling, sitting, crawling, walking
- Fine motor: small movements - grasping, pointing, using a pincer grip
- Cognitive: problem-solving, cause and effect, object permanence
Milestones by Age
| Age | Common milestones |
|---|---|
| 2 months | Smiles at people, follows objects with their eyes, calms when picked up |
| 4 months | Holds head steady, pushes up on arms during tummy time, babbles |
| 6 months | Sits with some support, rolls both ways, responds to their name |
| 9 months | Sits without support, crawls, picks up small objects with fingers |
| 12 months | Pulls to stand, may take first steps, says "mama"/"dada" or similar |
| 18 months | Walks independently, points to show interest, says several words |
| 24 months | Runs, uses short 2-word phrases, follows simple two-step instructions |
These are common examples, not a complete or required checklist. Babies often lead in one domain and lag slightly in another - that's typical, not a red flag on its own.
What If My Baby Seems a Little Behind?
The range of "normal" is wide, and a baby born early is generally assessed against their adjusted age (based on due date, not birth date) for the first couple of years. A single missed milestone rarely means much on its own - pediatricians look at the overall pattern across checkups, not any one skill in isolation.
When to Talk to Your Pediatrician
- No smiling or social response by around 3 months
- Not sitting with support by around 9 months
- No words at all by around 18 months
- Not walking by around 18 months
- Loss of a skill your baby previously had, at any age
Any of these is worth raising at the next visit - routine checkups are built around exactly this kind of tracking.
Frequently Asked Questions
What are the 5 domains of child development?
Social, language, gross motor, fine motor, and cognitive development are the five areas typically used to track a baby's progress.
Is it normal for a baby to be behind on one milestone?
Yes. Babies often develop unevenly across domains, and a wide range of timing is considered typical for almost every milestone.
What is a developmental red flag pediatricians watch for?
Losing a previously acquired skill, at any age, is generally taken more seriously than being a bit later on a new one - it's always worth mentioning to your pediatrician.
Related Reading
Milestones, tracked in Milli
Milli lets you track developmental milestones across all five domains from 0–24 months, so you can see your baby's overall progress in one place instead of trying to remember what happened when.