Early Signs of Autism in Toddlers: Age-by-Age Red Flags

If you are here at 3 AM, phone glowing, replaying your toddler’s “little quirks” like a highlight reel, I see you. As a pediatric nurse and a mom of three, I can tell you two things are true at the same time: toddlers develop on wildly different timelines, and your gut feeling deserves a calm, evidence-based reality check.

This guide walks through early signs of autism spectrum disorder (ASD) by age. It is not a diagnosis. Think of it as a way to organize what you are noticing so you can decide whether to watch, support at home, or ask for a formal evaluation.

First, a reassuring reality check

Autism is a neurodevelopmental difference that affects how a child communicates, connects socially, and experiences sensory input and routines. Many autistic children show signs in the toddler years, but some signs are subtle. Also, many non-autistic toddlers do one or two things on this list sometimes. The red flag is usually the pattern, the persistence, and the impact on daily life.

When I triaged kids in clinic, the most helpful information from parents was not “he flaps his hands.” It was “he flaps his hands a lot when excited, and he also does not point to show me things, and he rarely responds to his name.” Clusters matter.

One more thing I want to say clearly: the goal of evaluation and support is not to erase who your child is. It is to help them communicate, cope, and participate in daily life with less frustration, and to support your family along the way.

Age-by-age early signs of autism

Below are common developmental milestones and warning signs by age. If your child was born prematurely, their pediatrician may consider adjusted age for milestones, especially in the first two years.

At 12 months: social and communication

By around a year, many babies are busy becoming little social detectives. They look back and forth between you and interesting things, copy facial expressions, and use gestures before they have words.

Possible red flags around 12 months:

• Limited eye contact or eye contact that feels brief and hard to “catch” most of the time.
• Not consistently responding to their name (especially when hearing seems normal in other situations).
• Rarely smiles back at you or limited back-and-forth facial expressions.
• Limited gestures, such as rarely waving bye-bye, not reaching to be picked up, or not showing objects to you.
• Reduced babbling (few consonant sounds like “ba,” “da,” “ga”).
• Less sharing of enjoyment, like not looking at you to “check in” when something exciting happens.
• Unusual play with toys, such as repeatedly focusing on spinning wheels or parts rather than exploring the whole toy.

What to do now: If you are noticing several of these, bring it up at the next well visit. If you are noticing multiple concerns and your next visit is far away, it is reasonable to book a developmental check-in sooner.

At 18 months: gestures, joint attention, and words

Eighteen months is a big window for communication. Many toddlers use a handful of words, point to request things, and point to share interest, like “look at that!” This “joint attention” skill is a key early building block.

Possible red flags around 18 months:

• No words or very few meaningful words.
• Rarely points to show you something interesting (not just pointing to get snacks).
• Does not follow your point (you point at a dog, and they do not look where you point) most of the time.
• Limited imitation, such as not copying clapping, simple actions, or silly faces.
• More “in their own world” than expected, with fewer attempts to engage you during play across many days.
• Repetitive movements (hand flapping, rocking, spinning) that are frequent, intense, or hard to interrupt.
• Strong distress with small changes in routine beyond typical toddler protest, especially if it affects daily life.
• Sensory differences, like extreme distress with certain sounds, textures, hair washing, or strongly seeking sensory input (crashing, constant mouthing of non-food items) that disrupts routines.

Also consider hearing: “Not responding to name” and delayed speech can be related to hearing issues. Pediatricians often recommend a hearing check as part of an evaluation.

Bilingual homes note: Bilingualism does not cause autism. It can change which words show up first or how many words you hear in each language, but social-communication skills like gestures, joint attention, and back-and-forth engagement are still important to watch.

At 24 months: language and play

By two years, many toddlers start combining words and using language for a range of purposes: requesting, commenting, sharing feelings, and getting your attention. Play also often becomes more pretend-based, like feeding a doll or making a toy car “drive.”

Possible red flags around 24 months:

• No two-word phrases (not including repeating memorized lines), or very limited spontaneous speech.
• Language regression, meaning they had words or social skills and then lost them.
• Mostly repeating what they hear (echolalia) without flexible, back-and-forth communication. Echolalia can be part of typical development sometimes, but persistent reliance on it can be a flag.
• Limited pretend play (rarely feeding a doll, pretending to talk on a phone, “cooking”).
• Difficulty with back-and-forth interaction, like not taking turns in simple games most of the time.
• Intense interests in specific objects or topics, especially if it crowds out other play.
• Repetitive play patterns such as lining up toys and becoming very upset if the line is disturbed.
• Social differences, like rarely bringing you into play or not seeking comfort in the usual ways when upset.

Important: Some autistic toddlers are very affectionate and cuddly. Others are not. Autism is not defined by a child being “loving” or “not loving.” It is about patterns in communication, social connection, and flexibility.

At 36 months: social communication and flexibility

Three-year-olds are still three-year-olds, meaning meltdowns can happen in perfectly typical development. What stands out at this age is the ongoing pattern of social communication differences and difficulty with flexibility that makes daily life harder at home, daycare, or preschool.

Possible red flags around 36 months:

• Limited back-and-forth conversation or difficulty answering simple functional questions (for example, “What do you want?” “What’s your name?” “Where does it hurt?”).
• Difficulty playing with peers, such as not joining in, not engaging in pretend play with others, or preferring to play alone most of the time.
• Challenges with social cues, like not noticing when someone is upset or not adjusting behavior for different situations.
• Rigid routines or intense distress with transitions (leaving the house, changing activities) beyond what you would expect for age.
• Repetitive behaviors that remain frequent and interfere with play or learning.
• Sensory differences that significantly impact eating, dressing, grooming, or participating in typical activities.
• Pronoun mix-ups (saying “you” for “I”) can occur in autistic and non-autistic kids, but if paired with other signs it can add to the overall picture.

If preschool teachers are saying, “He is so smart, but he struggles with transitions and group time,” that feedback is worth taking seriously and bringing to your pediatrician.

Common signs across ages

If you prefer a simpler lens, many early autism signs fall into these buckets:

• Social connection: limited eye contact, limited sharing of enjoyment, fewer bids for attention, difficulty with back-and-forth interaction.
• Communication: delayed speech, limited gestures, less pointing to share, difficulty using language socially, repeating phrases without flexible use.
• Behavior and play: repetitive movements, repetitive play, intense interests, difficulty with changes and transitions.
• Sensory: strong reactions to sound, touch, textures, grooming, or seeking sensory input in ways that disrupt daily activities.

If you are worried today

• Message or call your pediatrician and ask for a developmental screening and referrals.
• Request a hearing check if speech or response-to-name is on your list.
• Contact Early Intervention (or your local early childhood developmental service) and ask for an evaluation.
• Start simple supports at home while you wait (see the “What you can do while you wait” section below).

When to request an evaluation

You do not need to “wait and see” if you have concerns. In pediatrics, we lean toward: when in doubt, check it out. Early supports can help with communication, behavior, and daily functioning, regardless of whether the final diagnosis is autism, a language delay, ADHD, anxiety, or something else.

Consider requesting an evaluation if:

• You notice multiple red flags in more than one category (social plus language, for example).
• Your child has lost skills they previously had (words, gestures, social engagement).
• Concerns are showing up in more than one setting (home and daycare or preschool).
• Your parenting instincts keep circling the same worries for weeks, not just a rough couple of days.

How to request an evaluation

1. Call your pediatrician and be specific. You can say: “I’m concerned about autism. My child is 18 months and does not point, has few words, and rarely responds to their name. I’d like a developmental screening and referrals.”
2. Ask about standardized screening. Per the American Academy of Pediatrics, autism-specific screening is recommended at 18 and 24 months, and anytime concerns arise. In many US clinics, this is done with the M-CHAT-R/F.
3. Screening versus diagnosis: A screener (like the M-CHAT-R/F) does not diagnose autism. It estimates likelihood and helps decide whether a child should have more evaluation.
4. Request a hearing evaluation if speech or response-to-name is a concern.
5. Ask for referrals. Depending on your area and insurance, this may include:
   • Early Intervention (EI) or your state’s birth-to-3 program
   • Developmental-behavioral pediatrics
   • Child psychology or neuropsychology
   • Speech-language pathology
   • Occupational therapy for sensory and daily skills
6. Self-refer to Early Intervention if available. In many places, parents can contact EI directly without waiting for a doctor referral. If you are in the US, search: “your state early intervention referral.”
7. Document what you are seeing. Bring notes: when it happens, how often, what helps, and what is hardest (transitions, meals, daycare drop-off).
8. Videos can help. If you can safely capture a short clip of the behavior or communication concern at home, it can be useful for clinicians.

If you are outside the US: ask your child’s primary care clinician about local early childhood developmental services and how to self-refer if that is an option where you live.

What an autism evaluation looks like

Families often worry an evaluation will be cold, judgmental, or overly clinical. Most are not. A quality evaluation is a combination of:

• Developmental history (milestones, behavior patterns, strengths)
• Observation and play-based interaction
• Standardized tools (often ADOS-2 or similar, depending on age and setting)
• Speech-language assessment when needed
• Hearing and vision checks as appropriate

You will also talk about supports. Even before a formal diagnosis, kids can often start services for speech, developmental delay, or sensory needs.

What you can do while you wait

Waitlists are real, and they are frustrating. While you are waiting, you can still support communication and connection in simple, low-pressure ways:

• Get face-to-face during play. Sit at their level and pause, giving them time to respond.
• Narrate simply. Short phrases beat long speeches. “Up.” “More bubbles.” “Car go.”
• Follow their lead for a few minutes a day. Join what they are doing instead of redirecting right away.
• Use gestures with words. Point, wave, and model “all done” and “more.”
• Make routines predictable. Toddlers often do better with warnings: “Two more slides, then car.”
• Praise communication attempts. Any attempt counts: a sound, a look, a hand you pull toward the pantry.

If you take nothing else from this page, take this: getting evaluated is not “labeling your child.” It is opening doors to support.

When it is not autism

Some concerns that can look like autism early on include:

• Hearing loss or frequent ear infections affecting hearing
• Speech and language delay without broader social differences
• Global developmental delay
• Anxiety or sensory differences
• ADHD (often clearer as kids get older)

The right next step is the same: screen, evaluate, and support.

Red flags to call about

• Any loss of speech, babbling, or social skills
• No babbling by about 12 months
• No single words by about 16 months
• No two-word phrases by about 24 months
• Not responding to sound or concerns about hearing

These are commonly cited developmental red flags (for example, CDC and AAP-aligned guidance), but ranges vary by child. If you are worried, it is still worth checking in even if your child is “close.”

If your child is having a medical emergency, trouble breathing, or you feel they are unsafe, seek emergency care. For developmental concerns, start with your pediatrician and Early Intervention.

A final word from a nurse mom

It is easy to spiral into “What did I do wrong?” You did not cause autism by missing a milestone chart, using the wrong cup, or letting them watch a little too much TV during a stomach bug week. Your job now is not perfection. It is noticing, advocating, and getting support early if it is needed.

If you want, write down the top three things you are seeing and the age they started, then bring that to your pediatrician. Clear, calm information is powerful.