About 1 in 31 children in the United States is identified with autism spectrum disorder, so if you’re watching your child and wondering whether certain behaviors are typical, you’re far from alone. The signs look different depending on your child’s age, and they fall into two broad categories: differences in social communication and repetitive or rigid patterns of behavior. Here’s what to watch for and what to do if something feels off.
Early Signs in Babies and Young Toddlers
Some signs can appear before a child’s first birthday, though they’re easy to miss because babies develop at different rates. The earliest red flags tend to involve social connection. A baby who doesn’t respond when you say their name, avoids eye contact, or doesn’t smile back when you smile at them may be showing early signs worth tracking. None of these alone means autism, but a pattern of missed social milestones is meaningful.
By 15 months, most children will hold up a toy or point at something just to share the experience with you. This behavior, called joint attention, is one of the most reliable early markers. If your child doesn’t share interests with you this way by 15 months, or doesn’t point to show you something interesting by 18 months, that’s a specific signal to bring up with your pediatrician.
Signs in Toddlers and Preschoolers
The signs tend to become clearer between ages 2 and 3, when the social demands of daily life increase. By 24 months, most children notice when someone is hurt or upset. By 36 months, they typically notice other children and want to join in play. A child on the autism spectrum may not do either of these things on that timeline, or may seem uninterested in other kids altogether.
Speech differences are common but not universal. Some children have delayed language. Others develop words on time but use them in unusual ways, like repeating phrases they’ve heard (called echolalia) instead of generating their own sentences. Some children lose words they previously had. This kind of regression, where a child stops using skills they’d already developed, is one of the more alarming experiences for parents, and it’s a well-recognized pattern in autism.
The second category of signs involves repetitive behaviors and rigid routines. You might notice your child:
- Lines up toys or objects and gets upset if the order is changed
- Plays with toys the same way every time, or focuses on parts of objects like wheels rather than playing with the whole toy
- Flaps their hands, rocks their body, or spins in circles
- Gets very distressed by small changes in routine
- Develops intense, focused interests in specific topics or objects
Sensory Differences
Many autistic children experience the world differently through their senses. Some are oversensitive: they gag on certain food textures, react strongly to loud noises or bright lights, or refuse to wear clothing made from specific fabrics. Others are undersensitive and seem to need more input than usual. They might constantly touch things, bump into objects, or not seem to register pain the way you’d expect. Some children are a mix of both, overwhelmed by certain sensations and seeking out others.
These sensory differences aren’t just quirks. They can drive meltdowns, food refusal, and daily struggles that parents often attribute to pickiness or behavior problems before they understand the underlying cause.
Why Girls Are Often Missed
Autism has historically been identified using a profile that fits boys more closely. Girls tend to have a quieter presentation, with less obvious repetitive behavior or behavior that shows up differently. A girl might not flap her hands, but she might have an unusually intense fixation on a specific topic that looks like a typical childhood interest from the outside.
Girls are also more likely to mask their differences in public. They imitate what other children do socially, even if they don’t fully understand it. They may share a smile or maintain better eye contact than the “classic” profile suggests, which leads teachers and even clinicians to rule out autism. The cost of this constant imitation is high. Girls who go undiagnosed often develop anxiety, depression, or low self-esteem because they’re working so hard to fit in without understanding why social interaction feels so exhausting. By the time they’re identified, the presenting concern is often the anxiety or depression rather than the autism underneath it.
What the Diagnostic Process Looks Like
A formal autism diagnosis is made by a doctor, psychologist, or other trained clinician using criteria from the DSM-5. To meet the diagnostic threshold, a child needs persistent differences in all three areas of social communication (back-and-forth interaction, nonverbal communication like eye contact and gestures, and building relationships) plus at least two types of repetitive or restricted behavior. These can include repetitive movements or speech, insistence on routines, intense fixated interests, or unusual sensory responses.
Your pediatrician may use a screening tool called the M-CHAT-R at your child’s well visits, typically around 18 and 24 months. It’s a short parent questionnaire. A score of 0 to 2 suggests low likelihood. A score of 3 to 7 indicates moderate likelihood and triggers follow-up questions. A score of 8 to 20 is considered high likelihood and leads directly to a referral. Screening is not a diagnosis, but it’s a useful starting point that can speed up the process.
One thing that confuses many parents: a medical diagnosis and a school eligibility determination are not the same thing. A medical diagnosis is based on whether your child meets symptom criteria. A school district’s determination depends on whether those symptoms interfere with learning. It’s entirely possible for a child to have a medical diagnosis of autism but not qualify for special education services, because the school team concludes the child can make academic progress without them. If you want both clinical support and school-based services, you may need to pursue each separately.
What to Do if You See These Signs
If your child is under 3, every state has a federally funded early intervention program you can contact directly. You don’t need a referral or a diagnosis to request an evaluation. Call your state’s early intervention program and say you have concerns about your child’s development. They’ll schedule an assessment to determine eligibility for services, which can include speech therapy, occupational therapy, and developmental support.
If your child is 3 or older, you can call any local public elementary school, even if your child doesn’t attend, and request an evaluation through the school system for preschool special education services. Again, you don’t need a diagnosis first.
Early intervention can significantly improve a child’s ability to learn new skills and navigate challenges. The earlier support begins, the more it can shape a child’s trajectory in school and daily life. If something about your child’s development doesn’t feel right, trust that instinct and start the conversation. Waiting to see if they “grow out of it” costs time that matters.