Watching your baby grow comes with plenty of little questions. Is your baby developing on time? Should they already be sitting, babbling, or reaching for toys? It's easy to worry when another baby seems to be hitting milestones sooner, but having a clearer idea of what to expect can make those worries easier to navigate.
Our baby milestones guide offers a helpful starting point for following your little one's progress. The CDC's Act Early milestones, developed with guidance from the American Academy of Pediatrics, give parents a clearer picture of the skills to look for and when it's worth bringing up a concern with their pediatrician.
Key Takeaways
- The Updated CDC 75% Standard: The CDC now focuses on milestones that at least 75% of children can achieve by a certain age, giving parents clearer developmental signs to follow.
- Monitoring vs. Screening: Everyday observations help you track your child's progress, while formal tools like ASQ-3, PEDS, and SWYC provide a closer look during developmental screening.
- Milestones from Infancy to Preschool: CDC checklists cover ages 2 months to 5 years, with key checkpoints for movement, communication, social skills, and learning. Premature babies should also be tracked using their adjusted age.
- Why Crawling Was Removed: Crawling is no longer on the CDC checklist because babies move in different ways and some skip crawling altogether. However, floor play and cross-body coordination remain important.
- Speech Milestones and Developmental Red Flags: CDC and ASHA use different timelines for expressive language, making it important to understand speech expectations and watch for signs such as lost skills, limited gestures, or uneven movements.
- Tracking Tools and Screening Schedules: The CDC Milestone Tracker app makes it easier to record new skills, while routine developmental screenings at 9, 18, and 30 months help identify concerns. Autism-specific screening is recommended at 18 and 24 months.
- Early Intervention and Parent Support: Under IDEA Part C, parents can contact their state's Early Intervention program directly for a free developmental evaluation without waiting for a doctor's referral.
The CDC Act Early Framework: Modern Pediatric Surveillance Principles
You see your baby learning new things every day, from making new sounds to reaching for toys. But when a skill seems slower to develop, it's natural to wonder whether everything is on track. The CDC Learn the Signs. Act Early. (LTSAE) program gives parents milestone checklists from 2 months to 5 years, covering social-emotional, language, cognitive, and physical development.
The 2022 Milestone Revisions: Shifting to the 75th Percentile Standard
One of the biggest changes came in 2022, when the CDC and American Academy of Pediatrics updated their developmental milestone checklists. Older charts generally used the 50th percentile, meaning around half of children had reached a particular skill by that age. This sometimes made it harder to tell when a missed milestone deserved closer attention.
The updated checklists use a 75th percentile benchmark, meaning at least three out of four children are expected to demonstrate each listed skill by that age. Led by Dr. Jennifer Zubler and published in Pediatrics, the revision followed a review of hundreds of clinical studies. This gives parents and healthcare providers a clearer point of reference when discussing a child's development.
The wording became more straightforward, too. Instead of phrases like "may begin to" or "starts to," each milestone now describes a specific action parents can recognize at home. The update also introduced dedicated 15-month and 30-month checklists, filling some of the gaps between earlier developmental checkpoints when communication and motor skills continue to change quickly.
Developmental Monitoring vs Standardized Developmental Screening
A lot of developmental progress happens during ordinary moments at home. Watching how your baby plays, responds to familiar voices, communicates, and moves around is part of developmental monitoring.
Developmental screening takes things a step further. It uses structured questionnaires to examine a child's skills more closely. Common tools include the Ages and Stages Questionnaires (ASQ-3), the Parents' Evaluation of Developmental Status (PEDS), and the Survey of Well-being of Young Children (SWYC). Parents usually complete these questionnaires by answering questions about what their child can do in everyday situations.
During recommended wellness visits, pediatricians review the responses to see whether any areas need further attention. A screening result is not a diagnosis, but it gives the doctor a clearer idea of whether additional evaluation is needed.
If something raises concern, you can discuss the results and next steps with your pediatrician. Our guide to evaluating developmental milestone delays offers more information about what to expect during this process.
Both approaches matter: your observations help build the picture of your child's development, while formal screening provides a more structured way to check their progress.
Navigating the Checklists: Ages Covered from 2 Months to 5 Years
From those first smiles to the day your little one starts putting words together, there's a lot of growing happening in just a few years. The CDC groups developmental milestones into four areas: social-emotional, language, cognitive, and physical development. Its checklists cover ages 2 months to 5 years, giving parents a simple way to follow their child's progress.
During the first year, the main checkpoints are at 2, 4, 6, 9, and 12 months. Each stage brings something new, from early smiles and better head control to babbling, sitting, and those first attempts to stand.
Critical Infancy Checkpoints: 2, 4, 6, and 9 Months
The early months go by quickly, and even small changes feel exciting. At 2 months, babies start smiling when you talk to them and making little sounds beyond crying. By 4 months, you'll hear more cooing and chuckles, along with steadier head control.
Around 6 months, rolling, reaching for toys, and laughing become part of everyday play. By 9 months, sitting without support and making repeated sounds like "baba" are some of the bigger changes.
If your baby was born prematurely, remember to use their adjusted age when following milestones. This accounts for the weeks they arrived early and gives you a more appropriate timeline during their first two years. Our guide to adjusted milestones for premature infants explains this in more detail.
| Age | Social & Communication | Thinking & Play | Movement | AAP Screening |
| 2–4 months | Smiles, coos, chuckles | Watches people and toys | Lifts and steadies head | Routine surveillance |
| 6–9 months | Laughs, babbles, responds to name | Explores toys, looks for dropped objects | Rolls, sits unsupported | Developmental screening at 9 months |
| 12–15 months | Waves, uses early words, points | Finds hidden toys, stacks blocks | Pulls up, cruises, takes first steps | Routine surveillance |
| 18–24 months | Uses more words, combines two words | Copies simple activities, identifies body parts | Walks, runs, kicks a ball | Developmental screening at 18 months; autism screening at 18 and 24 months |
| 30 months–3 years | Uses short conversations, plays with others | Follows simple directions, recognizes colors | Jumps, draws, dresses with some help | Developmental screening at 30 months |
| 4–5 years | Tells stories, takes turns in play | Counts, recognizes letters and numbers | Hops, catches a ball, buttons clothes | Routine surveillance |
Toddler and Preschool Gates: 12 Months Through 5 Years
After the first birthday, you'll start seeing more independence in everyday activities. Around 12 to 15 months, little ones begin using gestures to communicate what they want, taking a few steps, and experimenting with simple words. By 18 months, walking becomes more confident and their vocabulary continues to grow.
The second birthday brings another big change in communication. Children start putting two words together, such as "more milk," while becoming more interested in copying what adults do. By 30 months, many are using longer phrases and following simple two-step directions.
As children move into the preschool years, conversations become easier to follow and play with other children becomes more involved. Around 3 years, they start having short back-and-forth conversations. By 4 to 5 years, storytelling, counting, and taking turns in games become more familiar parts of everyday life.
Our comprehensive child development framework explores these changes in more detail, including the social, emotional, and learning skills children continue building as they get ready for school.
The Clinical Debates: Crawling, Word Counts, and the 'Wait and See' Dilemma
If you've ever compared your baby's progress with another little one, you know how quickly questions can come up, especially when different professionals seem to give different advice. The 2022 CDC milestone update brought some of these differences into focus, particularly around crawling and early speech.
The Crawling Controversy: Public Health Surveillance vs Pediatric Therapy
Why did the CDC remove crawling from its milestone checklist? Not all babies crawl in the same way, and some skip traditional hands-and-knees crawling altogether, choosing to belly-crawl, scoot on their bottoms, or move straight to pulling themselves up. Because of this variation, crawling was difficult to use as a consistent age-based milestone.
Physical therapists still recognize the value of crawling, as moving on hands and knees gives babies opportunities to build upper-body strength, balance, and coordination between both sides of the body.
So, if your baby skips crawling, there's no need to assume something is wrong, although it's worth paying attention to how they use both sides of their body. Consistently dragging one leg or favoring one side while moving deserves a closer look, and our clinical pediatric red flags guide covers other signs parents should know.
Expressive Language Thresholds: The 50-Word Debate (CDC vs ASHA)
Parents can also come across different speech expectations when checking developmental guides. The CDC places the 50-word milestone at 30 months, while the American Speech-Language-Hearing Association (ASHA) looks for children to use at least 50 words and begin combining words during the 19–24-month period.
This difference doesn't mean parents need to wait until 30 months to ask about their toddler's speech. If your 2-year-old uses fewer than 50 words or isn't putting two words together yet, it's worth discussing their language development with a pediatrician or speech-language pathologist.
And remember, communication isn't just about how many words your child says. Understanding familiar words and using gestures to express their needs are also important parts of early language development.
Digital Tracking Tools and Daily Safety: Apps, Checklists, and Sleep Health
Between doctor's appointments, there are plenty of little things parents notice about their baby's development. Keeping track of new skills doesn't have to mean writing everything down in a baby book, either. Digital tools make it easier to record these changes and have useful notes ready for the next pediatric visit.
The CDC Milestone Tracker App and 'Milestones in Action' Photo Library
The free CDC Milestone Tracker app gives parents an easy way to follow their child's development. You can create a profile for each child, go through age-based milestone checklists, and receive reminders about upcoming well-child visits.
Not sure what a particular milestone is supposed to look like? The app's Milestones in Action photo and video library provides visual examples of developmental skills, making it easier to understand the written descriptions. You can also print milestone summaries to bring along to your child's next appointment, giving your pediatrician a clearer picture of the skills you've been noticing at home.
Restorative Sleep and Safe Sleepwear for Active Explorers
As babies spend their days learning new movements and sounds, getting enough restful sleep remains an important part of their development. During sleep, the brain processes experiences and skills learned throughout the day, making a consistent and comfortable sleep routine especially valuable.
A safe sleep space is just as important as a comfortable bedtime routine. Follow our guidelines for safe infant sleep, keeping the crib free of loose blankets and other bedding that could pose a suffocation risk. For wearable sleepwear, choose a suitable TOG rating based on the nursery temperature rather than adding too many layers.
| Room Temperature | Recommended Sleepwear Rating | Suggested Base Layer |
| 74°F–78°F (23°C–26°C) | 0.5 TOG | Short-sleeve bodysuit or diaper |
| 69°F–73°F (21°C–23°C) | 1.0 TOG | Short- or long-sleeve bodysuit |
| 61°F–68°F (16°C–20°C) | 2.5 TOG | Footed sleeper or two-piece pajamas |
When choosing a sleep sack, look for a comfortable fit that gives your baby enough room to move their legs freely. Breathable fabric and a sleeveless design are also useful considerations, particularly as little ones become more active in their sleep.
If your baby develops a mild fever after vaccinations, their usual sleepwear layers may need adjusting to avoid overheating. Our guide to dressing a baby with a fever for sleep offers more guidance on keeping your little one comfortable at bedtime.
Taking Decisive Action: Screening Schedules, Red Flags, and Early Intervention
Keeping track of milestones is helpful, but knowing what to do when something seems off is just as important. Regular developmental screening gives parents and pediatricians a chance to discuss concerns early, rather than waiting until the next milestone checkpoint.
The AAP Universal Screening Schedule: 9, 18, and 30 Months
The American Academy of Pediatrics (AAP) recommends general developmental screening at 9, 18, and 30 months, alongside developmental surveillance during routine well-child visits. These check-ins give pediatricians a closer look at how children are moving, communicating, and learning as they grow.
Autism-specific screening is also recommended at 18 and 24 months, often using parent questionnaires such as the M-CHAT-R/F to look at early social communication and behavior.
If your baby happens to be sick around a scheduled visit, it's helpful to distinguish temporary symptoms from ongoing developmental concerns. Our guides to infant fever emergency warning signs and when to seek urgent care for fever explain when an illness needs prompt medical attention.
Non-Negotiable Red Flags and Direct Self-Referral to Early Intervention
Some developmental signs deserve attention without waiting for the next routine checkup. These include loss of previously learned skills, no social smiles by 6 months, no gestures by 12 months, no words by 16 months, or persistent asymmetrical movements. If you notice any of these changes, contact your pediatrician for an evaluation. Our guide to rapid infant breathing with fever also covers warning signs that require urgent medical attention.
Parents don't have to wait for a doctor's referral to seek developmental support. Under IDEA Part C, families can contact their state's Early Intervention program directly to request a free evaluation, without needing a formal diagnosis first.
Getting started is straightforward: use the CDC Act Early directory to find your local program and request a multidisciplinary evaluation. The state generally has 45 days from referral to complete the evaluation and develop an Individualized Family Service Plan (IFSP) for children who qualify. This plan outlines the early support and in-home services available to the family.
You know your baby better than anyone, so don't feel you need to wait until a concern becomes more obvious before bringing it up. Keeping track of what you notice and asking questions early is a good place to start.
