Baby Age Guides: Birth to 3 Years

Evidence-based guides for every stage of your baby's development. Each guide covers milestones, feeding, sleep, safety, and when to talk to your pediatrician.

Key takeaways

  • Every baby develops at their own pace — milestones have a range of normal
  • The AAP recommends formal developmental screening at 9, 18, and 30 months
  • Early intervention is free, available in every state, and most effective when started early
  • Adjusted age should be used for premature babies when assessing milestones
  • Talk to your pediatrician if you have any concerns — do not wait

Content reviewed against published AAP, CDC, WHO guidelines

Editorial policy

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Choose your baby's age group

0-1 Month

Newborn Period

Reflexes, feeding patterns, sleep cycles, and adjusting to life outside the womb.

1-3 Months

Early Infancy

Social smiling, head control, cooing, and establishing feeding and sleep routines.

3-6 Months

Active Discovery

Rolling over, reaching for objects, laughing, and introduction to solid foods.

6-9 Months

Getting Mobile

Sitting independently, crawling, babbling, and solid food exploration.

9-12 Months

Approaching Toddlerhood

Pulling to stand, first words, pincer grasp, and growing independence.

12-18 Months

Early Toddler

Walking, vocabulary growth, self-feeding, and exploring boundaries.

18-24 Months

Active Toddler

Running, two-word phrases, imaginative play, and asserting independence.

2-3 Years

Preschool Readiness

Sentences, potty training, social play, and preparing for preschool.

Related resources

Newborn GuideMilestones TrackerFeeding GuideSleep GuideVaccine ScheduleGrowth Calculator

Frequently asked questions

How do I know if my baby is meeting milestones on time?
The CDC publishes milestone checklists for each age. Most milestones have a range of normal. If your baby has not reached a milestone by the upper end of the expected range, talk to your pediatrician. Early intervention services are free and available in every state.
Should I worry if my baby skips a milestone like crawling?
Some babies skip crawling and go straight to walking. This is generally considered a normal variation. The AAP recommends focusing on whether your baby is progressing overall rather than checking off every single milestone in order.
When should I bring up developmental concerns with my pediatrician?
Bring up concerns at any well-child visit. Do not wait for the "right" age. The AAP recommends formal developmental screening at 9, 18, and 30 months, but you can request screening at any time.
Do premature babies hit milestones later?
Yes. Pediatricians use "adjusted age" (age from due date, not birth date) to assess milestones for the first 2-3 years. A baby born 2 months early would be expected to reach 4-month milestones at 6 months chronological age.

Bottom line

Development is not a race. These age guides provide general timelines based on CDC and AAP data, but every baby is unique. If you have concerns about your child's development, talk to your pediatrician — early support makes a real difference.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

All content follows our editorial policy and is reviewed against published clinical guidelines.

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