According to the CDC, most babies smile in response to voices by 2 months, hold their head steady by 4 months, roll from tummy to back by 6 months, sit unsupported by 9 months, and pull up to stand by 12 months. CDC developmental milestones represent skills that 75 percent or more of children achieve by each age. If your baby misses a milestone, consult your pediatrician promptly.
What are developmental milestones?
The CDC "Learn the Signs. Act Early." program defines developmental milestones as behavioral and physical abilities that most children (75 percent or more) demonstrate by a given age. A listed milestone reflects a skill achieved by the vast majority of babies by that point; many infants reach them earlier.
The CDC categorizes milestones into four key functional domains: social and emotional development, language and communication, cognitive learning and problem solving, and motor and physical movement.
Baby milestones chart from 2 to 12 months
| Age | Social, language, and cognitive skills | Movement and physical milestones |
|---|---|---|
| 2 months | Calms when spoken to or held; looks at faces; smiles when you smile; makes sounds other than crying; reacts to loud sounds | Lifts head when on tummy; moves both arms and both legs; opens hands briefly |
| 4 months | Smiles spontaneously to attract attention; makes cooing sounds ("ooo", "aaa"); turns head toward voices | Holds head steady unsupported when held; holds toys placed in hands; brings hands to mouth; pushes up onto elbows on tummy |
| 6 months | Knows familiar people; laughs; takes turns making sounds with parents; reaches for wanted objects | Rolls from tummy to back; pushes up with straight arms on tummy; leans on hands to support self when sitting |
| 9 months | May be shy with strangers; reacts to name; makes repetitive consonant sounds ("mamama", "bababa"); looks for hidden objects | Moves into a sitting position independently; sits without support; passes objects from one hand to the other |
| 12 months | Waves "bye-bye"; calls at least one parent by a specific name ("mama", "dada"); understands simple requests like "no" | Pulls up to stand; walks holding onto furniture; picks up small items using pincer grasp |
We cover motor milestones in newborn when to start tummy time and speech progression in baby milestones when to worry.
1 month baby development
The CDC milestones begin at 2 months rather than 1 month. During the first weeks, newborn development is evaluated through clinical pediatric visits. According to the UK National Health Service (NHS), babies are weighed during their first week, receive a comprehensive clinical examination within 72 hours of birth, and have a routine 6 to 8 week health check to evaluate weight, length, and head circumference.
2 month baby milestones
According to the CDC, most 2 month old infants look happy to see you, smile when you talk or smile at them, make cooing sounds, watch you as you move across the room, and lift their heads when lying on their stomachs.
5 month baby milestones
The CDC does not maintain a dedicated 5 month milestone checklist. Pediatricians evaluate 5 month infants using the 4 month and 6 month developmental markers together. Emerging 6 month skills include laughing, blowing raspberries, reaching for toys, and closing lips when full.
Milestones for premature infants
According to the NHS and CDC, for babies born prematurely (before 37 weeks of gestation), developmental age is calculated based on their estimated due date rather than their chronological birth date until age 2. Always share your baby's gestational age when discussing milestones with healthcare providers.
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When to consult a pediatrician
The CDC guidance is clear: do not wait. If your child has missed one or more age appropriate milestones, has lost previously acquired skills, or if you have concerns about their development, act early. The CDC recommends:
- Sharing your specific observations with your pediatrician and requesting developmental screening
- Asking for a referral to a pediatric developmental specialist if concerns persist
You know your child best. The American Academy of Pediatrics (AAP) recommends standardized developmental screening at 9, 18, and 30 months during routine well child visits. Seek emergency medical attention if your baby appears unusually floppy, unresponsive, or has severe breathing difficulty. In the US call 911; in the UK call 999; in Europe call 112.
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Frequently asked questions
Is a milestone checklist a formal developmental test?
No. The CDC emphasizes that informational milestone checklists do not replace standardized, validated developmental screening tools administered by healthcare providers.
What should you do if your baby loses an acquired skill?
According to the CDC, losing an ability your child previously possessed is an established clinical indicator to schedule an immediate evaluation with your pediatrician.
Sources
- CDC: Learn the Signs. Act Early. Milestones
- CDC: Milestones by 2 months
- CDC: Milestones by 4 months
- CDC: Milestones by 6 months
- CDC: Milestones by 9 months
- CDC: Milestones by 1 year
- NHS: Your baby's health and development reviews
Baby tracker
This tracker is not available in yuuvii 2.0.1. You can read articles on this topic here.
