Signs of Autism in Toddlers: What Parents Should Know
By Karen Chung | Special Learning | Evidence-based guidance for families
If you are reading this, you are probably worried about your child and looking for honest, clear information. That is exactly what this guide is for. I will walk you through the early signs of autism spectrum disorder (ASD) in toddlers, explain what the research says, and give you concrete steps you can take right now. No jargon, no vague reassurances.
Why Early Identification Matters
ASD affects approximately 1 in 36 children in the United States, according to the most recent data from the Centers for Disease Control and Prevention (CDC).1 It is one of the most common neurodevelopmental conditions in the world. The good news: decades of research consistently show that children who receive early, evidence-based intervention, particularly before age 5, tend to have significantly better long-term outcomes in communication, adaptive behavior, and quality of life.2
The challenge is that the average age of ASD diagnosis in the U.S. is still around 4 to 5 years, even though trained clinicians can reliably identify autism as early as 18 to 24 months.3 That gap represents years of missed early intervention. Your instincts as a parent matter. If something feels off, trust that feeling enough to act on it.
What Autism Actually Is (A Brief, Plain-Language Overview)
ASD is a neurodevelopmental condition characterized by differences in social communication and interaction, along with restricted or repetitive behaviors, interests, or sensory responses.4 "Spectrum" is the key word: ASD looks very different from one child to the next. One toddler may have no spoken words; another may have many words but struggle to use them in back-and-forth conversation. Some children are highly sensitive to sound or touch; others seem to seek intense sensory input.
ASD is not caused by parenting style, vaccines, or screen time. The current scientific consensus points to a combination of genetic and environmental factors that influence brain development.5
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Early Signs of Autism: Red Flags by Age
The following signs are drawn from validated research and clinical guidelines. Not every child who shows one of these signs has autism, and not every child with autism will show all of these signs. What matters is the overall pattern and whether you are seeing several of these behaviors together.
By 6 Months
- Rarely or never smiles back when you smile at them
- Limited or no eye contact during face-to-face interaction
- Little to no back-and-forth babbling or cooing
By 9 Months
- Not sharing sounds, smiles, or other expressions with caregivers
- Does not respond to their name when called
- Does not turn toward familiar voices
By 12 Months
- No babbling at all
- Does not point, wave, or gesture to communicate
- Does not respond consistently to their name
- Limited or absent joint attention (following your gaze, pointing to share interest in something)
By 16 Months
- No single meaningful words
- Not showing objects to share interest with caregivers
- Appears indifferent to other children
By 24 Months
- No two-word phrases that are spontaneous (not just repeating what someone else says)
- Unusual or rigid play patterns (lining up objects, intense focus on parts of toys rather than the whole toy)
- Repetitive body movements such as hand-flapping, rocking, or spinning
- Significant distress when routines change
- Unusual sensory responses (extreme sensitivity to noise, textures, lights, or seeking intense sensory input)
- Loss of any previously acquired language, babbling, or social skills at any age
- No eye contact
- Complete absence of pointing or other gestures by 12 months
Developmental Milestones at a Glance
The CDC and the American Academy of Pediatrics (AAP) publish updated developmental milestone guidelines. The table below summarizes key social-communication milestones most relevant to ASD screening, based on CDC's 2022 milestone checklist.6
| Age | Typical Social-Communication Milestones | Potential Red Flag if Absent |
|---|---|---|
| 6 months | Smiles back, recognizes familiar faces, begins babbling | No social smiling, limited eye contact |
| 9 months | Takes turns making sounds, uses gestures, responds to name | Not responding to name, no back-and-forth exchanges |
| 12 months | Points to show interest, waves bye-bye, says "mama/dada" meaningfully | No pointing or waving, no words, name not recognized |
| 18 months | 15 or more words, points to pictures in books, simple pretend play | Fewer than 6 words, no pointing to show interest |
| 24 months | 2-word phrases, parallel play near other children, follows 2-step directions | No spontaneous 2-word phrases, no imitation of others |
| 36 months | Simple conversations, plays with other children, uses "I" and "me" | No sentences, plays alone consistently, language regression |
Understanding Joint Attention: The Most Important Early Skill You May Not Have Heard Of
Joint attention refers to the ability to coordinate attention between a person and an object or event, sharing an experience. A typical 12-month-old points to a dog to share the excitement with you, then looks back at your face to see your reaction. This two-way sharing is foundational to language development and social learning.
Research has consistently identified reduced joint attention as one of the earliest and most reliable markers of ASD risk.7 If your toddler rarely or never points to share something interesting, shows you things to get your reaction, or follows your gaze when you look at something, that is worth noting and discussing with your pediatrician.
What About Regression? When Children Lose Skills They Already Had
Some parents notice that their child seemed to be developing typically and then lost skills, words disappeared, eye contact faded, a previously social child became withdrawn. This is called developmental regression, and it occurs in approximately 20 to 30 percent of children who are later diagnosed with ASD, typically between 15 and 24 months.8
Regression is always a reason to call your pediatrician promptly, not to wait for the next scheduled visit. It is not something to "wait and see" on. Regression can also signal other neurological conditions that require immediate evaluation, so do not delay.
Autism Screening Tools: What Happens at the Pediatrician's Office
The AAP recommends autism-specific screening at the 18-month and 24-month well-child visits, in addition to general developmental surveillance at every visit from birth.9 The most widely used screening tool in the U.S. is the M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised with Follow-Up).
The M-CHAT-R/F is a validated parent-report questionnaire with 20 yes/no questions about your child's behavior.10 If the initial screen indicates elevated risk, a clinician follows up with a structured interview to refine the risk level. A positive screen does not mean a diagnosis. It means your child should be referred for a comprehensive developmental evaluation.
If your pediatrician has not mentioned screening and your child is between 18 and 30 months, you can ask for it by name. You can also review our Developmental Screening Checklist to organize your observations before the appointment.
What To Do If You Are Concerned: A Step-by-Step Plan
Worry without action does not help your child. Here is a practical path forward.
Step 1: Document What You Are Seeing
Write down specific behaviors with dates. Take short videos on your phone during ordinary moments at home. Clinicians cannot always see these behaviors in a brief office visit, and your documentation is invaluable.
Step 2: Talk to Your Pediatrician Now
Do not wait for the next scheduled well-child visit if you are concerned. Call and ask for an appointment to discuss developmental concerns specifically. Bring your notes and videos.
Step 3: Request Referrals in Parallel
Ask for a referral to a developmental pediatrician or a multidisciplinary evaluation team. At the same time, request a hearing test (audiological evaluation). Hearing loss can mimic some signs of autism, and it needs to be ruled out.
Step 4: Contact Early Intervention Directly
Under the Individuals with Disabilities Education Act (IDEA), Part C, children under 3 years old are entitled to a free developmental evaluation and, if eligible, early intervention services. You do not need a diagnosis or a doctor's referral to contact your state's early intervention program. You can call or request a referral yourself. Find your state's program through the CDC's state early intervention directory.11
Step 5: Do Not Wait for a Diagnosis to Start Services
Early intervention services are available based on developmental need, not a confirmed diagnosis. If your child qualifies, they can begin receiving speech therapy, occupational therapy, or applied behavior analysis (ABA) services while the diagnostic process continues. Earlier is always better.
What Early Intervention Actually Looks Like
Early intervention for toddlers with or at risk for ASD can include speech-language therapy, occupational therapy (OT), developmental therapies, and ABA (applied behavior analysis). ABA, delivered through naturalistic and play-based approaches for very young children, has the strongest evidence base for improving communication, adaptive skills, and learning in children with ASD.2
For families navigating this for the first time, understanding the terminology can be overwhelming. Special Learning's parent guide to ABA therapy explains what it is, what it is not, and what to look for in a quality provider.
If you are already working with a Board Certified Behavior Analyst (BCBA) or looking for one, Special Learning's professional training library and our ESBAP certification program support practitioners who work with young children across 140+ countries.
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Frequently Asked Questions
What are the earliest signs of autism in babies and toddlers?
Early signs can appear in the first year of life and include limited eye contact, not responding to their name by 12 months, not pointing or waving by 12 months, loss of previously acquired language or social skills, and limited back-and-forth communication. The presence of any one sign does not mean a child has autism, but a cluster of these signs warrants a conversation with your pediatrician.
At what age can autism be reliably diagnosed?
Research shows autism can be reliably diagnosed in children as young as 18 to 24 months by experienced clinicians.3 The AAP recommends formal autism-specific screening at 18 and 24 months of age, in addition to general developmental surveillance at every well-child visit.9
What is the M-CHAT-R/F screening tool?
The M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised with Follow-Up) is a validated two-stage parent-report screening tool used to identify toddlers at risk for ASD between 16 and 30 months of age.10 It is commonly administered during well-child visits and is available in multiple languages. A positive result means your child should be referred for a full evaluation, not that they have a diagnosis.
My toddler has some of these signs. Does that mean they have autism?
Not necessarily. Many of these signs can be associated with other developmental differences, language delays, hearing loss, or individual variation in development. Only a qualified professional can make a diagnosis. However, if you notice several red flags, acting quickly is important because early intervention produces the best outcomes regardless of the final diagnosis.
What should I do if I am concerned about my toddler's development?
Start by talking to your child's pediatrician, calling sooner rather than waiting for the next scheduled visit if you are worried. Ask for a developmental screening and a referral for a comprehensive evaluation. Contact your state's early intervention program directly. Under IDEA Part C, you do not need a diagnosis or a referral to request a free evaluation for a child under age 3.
Does developmental regression always mean autism?
Not always, but it is a significant red flag that warrants prompt evaluation. Regression, meaning the loss of skills a child has already developed such as words or social responsiveness, occurs in roughly 20 to 30 percent of children later diagnosed with ASD.8 Regression can also be caused by other medical or neurological conditions, so do not wait to contact your pediatrician.
References
- Maenner, M.J., et al. (2023). Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years - Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020. MMWR Surveillance Summaries, 72(2), 1 - 14. Centers for Disease Control and Prevention. https://doi.org/10.15585/mmwr.ss7202a1
- National Autism Center. (2015). Findings and Conclusions: National Standards Project, Phase 2. National Autism Center. https://www.nationalautismcenter.org/national-standards-project/phase-2/
- Zwaigenbaum, L., et al. (2015). Early Identification of Autism Spectrum Disorder: Recommendations for Practice and Research. Pediatrics, 136(Suppl 1), S10 - S40. https://doi.org/10.1542/peds.2014-3667C
- American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR). American Psychiatric Association Publishing. https://www.psychiatry.org/psychiatrists/practice/dsm
- Tick, B., Bolton, P., Bishop, D. V. M., Happé, F., & Rijsdijk, F. (2016). Heritability of autism spectrum disorders: A meta-analysis of twin studies. Journal of Child Psychology and Psychiatry, 57(5), 585 - 595. https://doi.org/10.1111/jcpp.12499
- Centers for Disease Control and Prevention. (2022). CDC's Developmental Milestones. CDC. https://www.cdc.gov/ncbddd/actearly/milestones/index.html
- Mundy, P., & Newell, L. (2007). Attention, Joint Attention, and Social Cognition. Current Directions in Psychological Science, 16(5), 269 - 274. https://doi.org/10.1111/j.1467-8721.2007.00518.x
- Ozonoff, S., et al. (2010). Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study. Pediatrics, 128(3), e488 - e495. https://doi.org/10.1542/peds.2010-2825
- Hyman, S.L., Levy, S.E., Myers, S.M., & Council on Children with Disabilities, Section on Developmental and Behavioral Pediatrics. (2020). Identification, Evaluation, and Management of Children with Autism Spectrum Disorder. Pediatrics, 145(1), e20193447. https://doi.org/10.1542/peds.2019-3447
- Robins, D.L., Casagrande, K., Barton, M., Chen, C.A., Dumont-Mathieu, T., & Fein, D. (2014). Validation of the Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F). Pediatrics, 133(1), 37 - 45. https://doi.org/10.1542/peds.2013-1813
- Centers for Disease Control and Prevention. (2023). Find Your State's Early Intervention Program. CDC Act Early. https://www.cdc.gov/ncbddd/actearly/parents/states.html