Check the milestones
How to use a milestones checklist
Milestones checklists work best as conversation starters, not examinations. In 2022 the CDC revised its Learn the Signs. Act Early. materials with an important change in philosophy: the checklists now list what 75 percent or more of children can do by each age, replacing the older 50-percentile lists. The practical meaning is straightforward: if your child is not doing something that three-quarters of children can do by this age, it is worth discussing, even though a quarter of children also cannot do it yet.
Use the checklist at the age closest to your child's current age, ticking what you have actually seen rather than what you think they could do. Children perform differently for parents and for strangers, on good days and bad days, so observe over a week rather than staging a single test session. And remember the checklist covers four domains for a reason: a child can be ahead in movement and behind in language, and each domain deserves its own attention.
Premature babies need adjusted ages: subtract the weeks of prematurity from the chronological age until at least age two, and use the adjusted age on the checklist. A baby born 8 weeks early who is 6 months old chronologically is 4 months developmentally, and should be judged against the 4-month milestones.
The four domains
Social and emotional milestones track how the child connects: smiling, enjoying people, showing affection, playing alongside and then with other children, understanding feelings. These are often the earliest window into developmental differences, including autism, which is why the checklists weight them heavily.
Language and communication covers both understanding and expression, from reacting to sounds through first words to sentences and conversation. Receptive language (understanding) normally runs ahead of expressive language (talking), so a child who understands everything but says little is a different case from one who neither understands nor speaks.
Cognitive milestones track thinking and learning: exploring objects, finding hidden toys, sorting shapes, pretend play, counting and early problem-solving. Movement and physical milestones track gross motor (rolling, sitting, walking, running, jumping) and fine motor (grasping, stacking, drawing, using utensils) skills. Motor milestones are the most visible and the most often worried about, but isolated mild motor delay with normal other domains is frequently benign.
When missing milestones matter
Three patterns should prompt action rather than waiting. First, missing multiple milestones in any domain at the 75-percent threshold: book a developmental review. Second, uneven development with a big gap between domains, such as normal motor skills with markedly delayed language, which can signal specific conditions. Third and most urgent, regression: losing any previously acquired skill, whether language, social or motor, at any age. Regression is never normal waiting and always needs prompt assessment.
The pathway after concern is surveillance, then screening, then assessment. Your clinician may use a validated screening tool such as the Ages and Stages Questionnaire or the M-CHAT for autism concerns, and refer to early intervention services, speech therapy, or developmental paediatrics. The evidence is clear that earlier intervention works better, which is why guidelines say to act on parental concern rather than waiting to be sure.
Milestones by age: what the checklist covers
The checklist spans 2 months to 5 years across 12 age points. At 2 months the milestones are about calming, smiling and early sounds; by 6 months the baby rolls, babbles and reaches. 9 to 12 months brings first words, waving, pulling to stand and the pincer grasp. 15 to 18 months adds walking, pointing, several words and simple pretend play.
By 2 years most children use two-word phrases, follow two-step instructions, run and kick a ball. 30 months brings short sentences and turn-taking; 3 years brings conversation, pedalling a tricycle and drawing circles. 4 years adds storytelling, hopping and naming colours; by 5 years most children count to ten, print some letters, dress themselves and play cooperatively. Each age point in the calculator lists the full CDC set for that age.
Supporting development every day
The most powerful developmental intervention is also the simplest: responsive, talkative, playful caregiving. Talk with your child through the day, not just to them: narrate what you are doing, respond to their babbles and gestures as if they were conversation, read together daily from infancy, and give plenty of floor time for movement. Screen time displaces all of these and should be limited, especially under 18 months, with any viewing watched together rather than alone.
Play is the curriculum. Simple, open-ended toys, outdoor time, other children and boredom all teach more than electronic toys that do the playing for the child. And look after the basics that development rests on: adequate sleep, good nutrition including iron, treated hearing and vision, and a calm, predictable environment. Development is robust, but it is not indestructible, and the everyday environment is its main ingredient.
Key takeaways
- The CDC 2022 checklists list what 75 percent or more of children can do by each age.
- Missing milestones at that threshold merit discussion, not panic; patterns matter more than single items.
- Loss of any previously acquired skill at any age needs prompt assessment, always.
- Adjust age for prematurity until at least age two before using the checklist.
- Act on concern early: early intervention works better, so do not wait to be sure.
Frequently asked questions
My 18-month-old is not talking yet. Should I worry?
The 18-month CDC milestones include saying several single words. A child of 18 months with no words deserves a hearing check and a developmental review, not a wait-and-see of many more months. That said, understanding (pointing, following instructions) matters enormously: a child who understands well but speaks little is less concerning than one with both delayed, and boys and multilingual children can be slightly later. Book the review.
Do bilingual children hit milestones later?
Slightly, for expressive language only, and only temporarily. Bilingual children may say first words a little later and mix languages, but their total vocabulary across both languages is normal and their understanding is unaffected. Do not drop a home language on professional advice to speed things up; the evidence supports bilingualism.
My baby was premature. Which age do I use?
Subtract the weeks of prematurity from the chronological age until at least the second birthday. A baby born 2 months early who is 10 months old is 8 months developmentally for milestone purposes. Most catch up by age two, though some need longer, which the paediatrician will track.
Are the milestones different for boys and girls?
Only trivially. Girls are on average very slightly ahead in early language and boys in some motor skills, but the differences are small and the same checklists apply to both. A large gap attributed to sex alone should not reassure; use the checklist as written.
The checklist says my child is behind but my doctor is not worried. Who is right?
Possibly both. The checklist is a screening aid using a 75-percent threshold; your doctor integrates the trend, the examination, family patterns and clinical experience. But parental concern is itself a validated screening instrument: if you remain worried after discussion, ask what specifically is reassuring, when to recheck, and what would change the plan.