Tiny Milestones guides

What a developmental milestone is, and what it isn't

A developmental milestone is a skill most children show by a certain age: a first smile, a first step, a wave bye-bye. The CDC's checklists put each one at the age by which at least 75 percent of children do it, so that a missed milestone is worth a conversation with the doctor. Milestones are for watching and talking; they are not a test, a diagnosis, or a standard your baby has to meet.

A skill you can see

The CDC's definition is plain: skills such as taking a first step, smiling for the first time, and waving bye-bye are called developmental milestones, and children reach them in how they play, learn, speak, act, and move¹. The CDC's checklists sort them into four groups: social and emotional, language and communication, cognitive, and movement².

What the age means

Each milestone on the CDC's 2022 checklists sits at the age by which at least 75 percent of children are expected to show it. The placement came from a published 2019 review of the evidence, together with the authors' clinical judgment³⁴. The CDC chose 75 percent rather than the average age so that even one missing milestone is "actionable": at the average, half of all children would not have the skill yet, and a late one gets a "wait and see" instead of a conversation³.

Two things follow. A CDC age is one point, not a range, and most babies reach the skill before it. And the lists are not complete: a milestone that isn't on them was left out for lack of published evidence, not because it doesn't matter³.

What a milestone is not

The CDC is explicit that its milestones are not developmental guidelines or standards, and should not be used as screening or diagnostic tools³. They are communication tools, meant to start conversations between families and professionals, and they are no substitute for the standardized, validated screening tools a doctor uses¹³. The difference matters: monitoring is watching how a child grows and changes over time, with a simple checklist; screening is a formal test given at set ages or whenever there is a concern⁵. The American Academy of Pediatrics recommends general developmental screening at 9, 18, and 30 months, and autism screening at 18 and 24 months¹.

Early and late are both normal

Windows for the same skill are wide. In the WHO's study of healthy children, walking alone began anywhere from about 8 to 18 months⁶. For a baby born more than 3 weeks early, pediatricians count age from the due date for the first 2 years, which moves every milestone later on the calendar⁷. Our guide to adjusted age explains how.

When to act early

The CDC's guidance, which it prints on every checklist: you know your child best, so don't wait. If your child isn't meeting one or more milestones, has lost skills they once had, or you have other concerns, talk with your child's doctor, share your concerns, and ask about developmental screening. If you or the doctor are still concerned, ask for a referral to a specialist, and call your state or territory's early intervention program¹. Early intervention means services and supports, such as speech, physical, or occupational therapy, for babies and young children with delays or disabilities; every state and territory has a program, free or at reduced cost for children who qualify⁸. When concerns are found early and children get the services they need, they do better⁵.

What to do with milestones at home

The CDC encourages families to watch for milestones, celebrate them, and share progress with the child's doctor at every well visit⁵. A note of the date each first happened, with a photo if you like, makes that visit easier and gives you a record worth keeping.

The CDC's milestone checklists are free at cdc.gov. Our summary of them implies no endorsement by the CDC, HHS, or the U.S. Government.

This is general information, not medical advice. Ask your baby's doctor about your own baby.