Most babies hit major milestones within a wide range of “normal,” and the fact that your child hasn’t done something yet doesn’t necessarily mean there’s a problem. Developmental delay is formally defined as failing to reach milestones in two or more areas, such as movement, language, and social skills, within the expected age range. But many children who seem behind at one checkup are perfectly on track a few months later. Here’s how to tell the difference between a baby who’s taking their time and one who may need extra support.
What Counts as a Developmental Delay
Pediatricians look at five broad areas when evaluating development: movement (gross and fine motor), communication, cognitive skills, social and emotional behavior, and daily living skills like feeding. A child is considered to have a global developmental delay when they fall significantly behind in two or more of these areas. Falling behind in just one area, like walking a little late, is common and often resolves on its own.
A delay is also not the same as a disability. Delays can be temporary. Many kids catch up completely, especially with early support. A developmental disability, by contrast, involves lasting limitations in intellectual or adaptive functioning. At your baby’s age, no one can tell you with certainty which category your child falls into, which is why screening and follow-up matter so much.
Motor Milestones: Crawling, Standing, Walking
Babies vary enormously in when they start moving. Some walk as early as 9 months, while others don’t take independent steps until 15 months, and both are completely typical. By their first birthday, most babies are pulling to stand and “cruising” (walking while holding onto furniture). Independent walking by 15 months is the benchmark most pediatricians use.
If your baby isn’t pulling to stand by 12 months or isn’t walking independently by 18 months, that’s worth bringing up with your pediatrician. But keep in mind that babies who walk early aren’t necessarily ahead overall, and late walkers aren’t necessarily behind. Some babies invest their energy in language first and get to walking later.
Speech and Language: What to Expect by Age
Language milestones tend to cause the most anxiety because the range is so broad. Here’s what Children’s Hospital of Philadelphia considers typical at each stage:
12 to 17 months: Your baby should have a vocabulary of about four to six words (pronunciation doesn’t need to be clear). They should try to imitate simple words, follow one-step commands when you use a gesture, and respond to simple questions by shaking their head or going to get something. They should also enjoy being read to.
18 to 23 months: Vocabulary grows to around 50 words, though many will still be hard to understand. Your toddler should start combining two to three words into short phrases like “more milk,” make animal sounds, ask for foods by name, and point to body parts when asked. They should understand simple yes-or-no questions.
By age 2: Most children use at least 100 words and speak in three- to four-word sentences. They can follow two-step instructions (“Get your shoes and come here”), use pronouns like “me” and “you,” and ask questions by changing their tone of voice. Their pronunciation is improving but still rough around the edges. Strangers may not understand much of what they say, and that’s normal.
If your 18-month-old isn’t using any words at all, or your 2-year-old isn’t combining words into short phrases, those are signs to get a screening.
Social and Emotional Red Flags
This is the area where parents often wonder about autism. A speech delay alone doesn’t point to autism, but when it shows up alongside certain social behaviors, it can be a signal worth investigating. The key behaviors to watch for involve something called “joint attention,” which is your baby’s ability to share focus with you on the same thing.
A typically developing baby will point at something far away to get your attention (“Look at that dog!”), show you objects just for the fun of sharing the moment, and follow your gaze when you look across the room. A baby at higher risk for autism may not do these things. They may only bring you objects when they need help, rather than to share enjoyment. They may not point at things to direct your attention. They may not follow where you’re looking or pointing.
Another important marker is name response. By 12 months, most babies turn to look when you call their name. A baby at risk for autism may not respond even after several attempts, including when you’re close by or lightly touching them. If you’re noticing a cluster of these behaviors alongside limited speech, bring them up with your pediatrician specifically.
If Your Baby Was Born Early
Premature babies get a developmental grace period. Pediatricians use an “adjusted age” (also called corrected age) to evaluate preemies until they’re 2 years old. The calculation is simple: subtract the number of weeks your baby was born early from their actual age. So a 10-month-old who was born 6 weeks early would be evaluated as a roughly 8.5-month-old.
This matters a lot. A preemie who isn’t walking at 12 months of actual age may be right on schedule for their adjusted age. By age 2, most preemies have caught up to the typical milestone range. Until then, always use the adjusted age when comparing your baby to milestone charts.
How Screening Works
If you bring up a concern at a well-child visit, your pediatrician will typically start with developmental monitoring: observing your child, asking you questions about what they can and can’t do, and checking whether they’re hitting milestones most children their age have reached. If something looks off, the next step is a formal screening.
One of the most common screening tools is the Ages and Stages Questionnaire (ASQ-3). It’s a parent-completed questionnaire that covers communication, gross motor, fine motor, problem-solving, and personal-social skills. For each item, you answer “yes,” “sometimes,” or “not yet,” and the scores determine whether your child falls in the typical range or needs further evaluation. About 30% of babies score below the cutoff in at least one area, so a low score in one domain doesn’t automatically mean something is wrong. It means more assessment would be helpful.
If screening does flag a concern, your pediatrician will typically refer you to your state’s early intervention program for a more thorough evaluation. You don’t need a referral from a doctor to access this. Any caregiver can contact their state’s early intervention system directly and request an assessment.
Early Intervention: What It Looks Like
In the United States, children under 3 who have a developmental delay or a diagnosed condition that’s likely to cause one are eligible for early intervention services under Part C of the Individuals with Disabilities Education Act (IDEA). Eligibility is based on an evaluation showing delay in one or more areas: cognitive, physical, communication, social/emotional, or adaptive development.
Early intervention typically involves therapists coming to your home or your child’s daycare to work on specific skills. Depending on the area of delay, this might be a speech-language pathologist, an occupational therapist, or a physical therapist. Sessions are play-based and designed to fit into your child’s daily routine. The therapist also coaches you on strategies to use between visits, which is where much of the progress actually happens.
The evidence strongly favors starting early. The brain is most adaptable during the first three years of life, and children who receive support during this window tend to make more progress than those who start later. If your gut is telling you something is off, requesting an evaluation costs nothing and commits you to nothing. The worst outcome of an unnecessary evaluation is reassurance.