Tracking your baby's first-year development is one of the most exciting — and most anxiety-inducing — parts of parenting. Should they be crawling already? Why aren't they saying "mama" yet? This guide summarizes what to expect month by month, based on the updated CDC and American Academy of Pediatrics (AAP) milestones, revised in 2022 and published in Pediatrics by Zubler and colleagues. The new logic is simple: each milestone represents the age by which at least 75% of children can do it — making it easier to know when it's worth a conversation with the pediatrician.
Before you start: three principles
- Milestones are ranges, not exact dates. One baby may walk at 10 months and another at 16; both can be perfectly healthy. Pace varies.
- Trajectory matters, but don't ignore a single missed milestone. Because the current criterion is 75%, a missed milestone for the age is enough for the CDC to recommend a conversation with the pediatrician (the Act Early campaign). Multiple delays in the same area or loss of skills require priority evaluation.
- Corrected age for preemies. Babies born before 37 weeks are evaluated by corrected age (chronological age minus weeks of prematurity) during the first 2 years.
The 2022 CDC revision dropped the old "50% of children" criterion and moved to 75%. In practice, that means today's published milestones are points where the vast majority of children have already arrived — and missing them is more informative than under the old criterion.
0 to 2 months: the world coming into focus
In the first weeks, your baby goes through a radical adaptation: breathing, regulating temperature, learning to feed. The nervous system is still organizing stimuli.
| Domain | What to expect by 2 months |
|---|---|
| Gross motor | Briefly lifts head when on tummy; smoother arm and leg movements |
| Fine motor | Keeps fists closed; opens hands for short periods |
| Language | Reacts to loud sounds; makes sounds other than crying ("ah", "ooh") |
| Cognitive | Looks at faces; follows objects with eyes for short distances |
| Social/emotional | Social smile (smiles back at you) — the first big emotional milestone; calms when picked up |
Red flags at 2 months (CDC): doesn't react to loud sounds; doesn't lift head when on tummy; doesn't watch moving objects; doesn't bring hands to mouth; doesn't smile at people.
2 to 4 months: discovering their own body
This is when the baby "wakes up" to the world. Hands become toys, sounds multiply, and smiles become real connection tools.
| Domain | What to expect by 4 months |
|---|---|
| Gross motor | Holds head steady when on your lap; props on forearms when on tummy; starts rolling from tummy to side |
| Fine motor | Holds objects for a few seconds; brings hands to mouth; brings hands to midline |
| Language | Coos and babbles ("aa", "oo"); turns head toward voices; laughs out loud |
| Cognitive | Looks at own hands with interest; recognizes familiar people from a distance |
| Social/emotional | Smiles spontaneously (not only in response); imitates simple facial expressions |
Red flags at 4 months: doesn't make sounds; doesn't bring objects to mouth; doesn't hold head steady; doesn't respond to smiles; one eye persistently turning in or out.
4 to 6 months: the motor turn
Your baby gains trunk control, discovers that hands can grab things and starts realizing actions cause reactions. For many parents, this is when the baby "becomes a person."
| Domain | What to expect by 6 months |
|---|---|
| Gross motor | Rolls from tummy to back; sits with support; pushes up on extended arms when on tummy |
| Fine motor | Reaches for and grabs a toy they want; brings objects to mouth |
| Language | Babbles repeating sounds ("ba-ba", "da-da" without meaning yet); reacts to own name with a glance |
| Cognitive | Examines nearby objects with curiosity; mouths everything to explore |
| Social/emotional | Recognizes familiar faces; knows who is a stranger; laughs during play |
Red flags at 6 months: doesn't reach for nearby objects; doesn't react to ambient sounds; doesn't roll from tummy to back; seems very floppy (hypotonia) or very stiff; doesn't make vowel sounds.
6 to 9 months: mobility and intentionality
The baby starts moving with purpose. Sits alone, maybe crawls (or scoots, or rolls — all valid), and discovers cause and effect: banging a spoon on the table makes noise, and that's amazing.
| Domain | What to expect by 9 months |
|---|---|
| Gross motor | Sits without support; moves between sitting and lying down; many begin to get around (crawling, rolling, scooting) — though crawling is no longer an official CDC milestone |
| Fine motor | Picks up small bits of food with all fingers against the palm (raking grasp); passes objects from one hand to another |
| Language | Says repeated syllables ("baba", "papa", "mama") without meaning yet; babbles with varied intonation as if "talking" |
| Cognitive | Looks for partially hidden objects (object permanence emerging); looks when you call their name |
| Social/emotional | Reacts differently to familiar people vs. strangers; may show separation anxiety; smiles or laughs during games like peekaboo |
Red flags at 9 months: doesn't sit without support; doesn't respond to name; doesn't make consonant sounds (b, m, p); doesn't search for objects you hide in front of them; doesn't exchange affectionate looks.
About crawling: in the 2022 revision, the CDC removed crawling from official milestones due to lack of consistent normative data — many healthy babies skip it and go straight from sitting to standing. Not crawling, by itself, is no longer a red flag. What matters is that the baby moves somehow and progresses toward locomotion.
When to bring it up urgently: if you notice loss of skills the baby already had (stopped babbling, stopped social smiling, stopped trying to move), schedule a visit soon. Regressions are important red flags at any age.
9 to 12 months: communication and first steps
The last phase of the first year combines a communication explosion with locomotion. The baby starts understanding words, pointing, and for many, taking first steps. For others, walking comes only at 14, 15, or 16 months — also within the normal range.
| Domain | What to expect by 12 months |
|---|---|
| Gross motor | Pulls to stand using furniture; walks sideways holding furniture (cruising); some take first independent steps |
| Fine motor | Pincer grasp (picks up crumbs with thumb and index finger); bangs two objects together; puts things into containers |
| Language | Says "mama" and "dada" with meaning (calling parents); understands simple commands paired with gestures ("come", "give"); imitates sounds you make |
| Cognitive | Looks for objects they saw you hide; puts something into a container, like a block in a cup |
| Social/emotional | Plays clap-hands or wave bye-bye; offers toys to you; shows clear preferences; "knows" when something is different |
Red flags at 12 months (CDC): doesn't pull to stand with support; doesn't say simple words like "mama" or "dada" with meaning; doesn't point or imitate gestures like waving; doesn't search for objects you hid in front of them; doesn't consistently respond to their name.
When — and how — to talk to the pediatrician
The AAP recommends standardized developmental screening at the 9-, 18- and 30-month visits, with tools like the ASQ. Between visits, the pediatrician does surveillance at every appointment: asks, observes, notes. If you have any concern, don't wait for the next routine visit — schedule one.
Seek guidance when you notice:
- Any missed milestone for the age — under the current 75% criterion, it's worth the conversation
- Multiple delayed milestones in the same area (motor, language, social) — priority
- Loss of skills already acquired at any age — priority
- Marked differences between the two sides of the body (one hand always closed, one leg used more than the other)
- No eye contact or no response to social interaction
- Your gut. Parents often notice signs before professionals do. Trust it and investigate.
When you book the visit, bring records — milestone dates, short videos of the baby in action, notes on what changed. Tools like Buppi help with exactly this: each milestone becomes a dated point on the timeline, easy to share with the pediatrician.
Four things that help development — without forcing or accelerating
The research is clear: what helps a baby reach milestones isn't early stimulation with flashcards or classes, but the basics done well.
- Tummy time from the first weeks, several times a day. Strengthens neck, shoulders and trunk — the base for rolling, sitting, crawling.
- Continuous talking. Narrating what you're doing ("now I'm changing your diaper", "look at the dog!") increases language exposure. That exposure predicts vocabulary at age 2.
- Shared reading every day, even in the first months. The AAP recommends it from birth.
- Unstructured floor play. Safe space, simple toys, time. The baby does the rest.
The phrase that matters more than any milestone
Milestones are useful — they help identify when something needs attention. But typical development has a wide range, and each baby arrives in their own time. If the pediatrician evaluated and everything is fine, and the baby interacts, smiles, explores and gains weight, comparison with the neighbor's child helps with nothing.
The question that matters, every month: is my baby progressing, in their own way? Almost always, the answer is yes.