Signs of Autism in Toddlers

Michael Mohan

August 15, 2025

Signs of autism in toddlers can be subtle, from delayed speech to unique play patterns, and spotting them early can make a big difference

As parents, we naturally monitor our children’s development, celebrating each milestone and occasionally worrying when things don’t seem quite right. When it comes to autism spectrum disorder (ASD), early recognition of warning signs can make a profound difference in a child’s developmental trajectory. About 1 in 31 (3.2%) children aged 8 years has been identified with ASD according to estimates from CDC’s ADDM Network, making autism one of the most common developmental conditions affecting children today.

Prevalence increased from one in 150 in 2000 to one in 36 in 2020, highlighting both increased awareness and improved diagnostic capabilities. Perhaps more importantly, early identification of ASD can help children receive services and supports they might need for their development and to improve long-term outcomes.

Understanding what to look for during those crucial early years can empower parents to seek timely evaluation and intervention when needed. This comprehensive guide will walk you through the key warning signs, provide practical examples, and explain why early detection matters so much for your child’s future.

Understanding Autism Spectrum Disorder in Toddlers

Autism spectrum disorder is a neurodevelopmental condition that affects communication, social interaction, and behavior. ASD is over 3 times more common among boys than among girls, though it’s important to note that autism can present differently in girls, sometimes making it harder to identify.

Some of the signs of autism may be noticed before the age of 1, though it can be difficult to recognise that a child is on the spectrum until they are between 18 and 22 months of age. This timing aligns with when many key developmental milestones typically emerge, making deviations more apparent to parents and healthcare providers.

Research shows that by age 2, an ASD diagnosis by an experienced professional can be considered reliable. However, many children show symptoms of autism by 12 months to 18 months of age or earlier, emphasizing the importance of being vigilant during these critical early months.

Key Warning Signs by Age Group

12-18 Months: The Critical Window

12 – 18 months of age is the most critical time to identify red flags in your child’s development. A formal autism diagnosis is typically given around 2-years of age so if you notice some of the signs below, please arrange for a formal medical diagnostic evaluation to confirm or rule out autism.

Social Communication Red Flags:

Limited eye contact: Your baby rarely makes eye contact with you and other loved ones. Babies tend to naturally look at and look for their parents and other caregivers. In addition, they may tend to recognize unfamiliar faces and move closer to those who are familiar or show “stranger danger”. Start to notice if your child is looking for you and exhibiting stranger danger; if they are not, it could be an early sign of autism
Lack of gestures: Around 12 – 14 months of age, babies become eager to use gestures as a form of communication. Most babies will use close to 16 gestures by 16 months. The most common gesture is pointing. If your child has no gestures or limited gestures by 18-months, this might indicate a concern
Minimal imitation: At around 8 months of age, your child should start imitating simple gestures. If your child is not imitating by the time they are 18 months old, it could be a sign of autism. Imitation is critical for language development, so it is important to model different actions for your baby to imitate and begin monitoring if imitation is not occurring

Language Development Concerns:

Delayed babbling or speech: Children with autism may not babble or produce recognizable words until they begin obtaining therapy (e.g., ABA therapy or speech therapy). Lack of babbling or speaking is a core feature of autism and identifying a concern with speech early will be critical to begin treatment early
Unusual vocal patterns: When a child at-risk for autism vocalizes, the voice might not vary in pitch, tone, or volume

Behavioral and Social Patterns:

Preference for objects over people: Babies are eager to interact with people, especially those they know and have a great rapport with. Children with autism often show signs such as preferring to be alone with a preferred object for a long period of time. Often, people will say “they are in their own world.” Begin noticing if objects are preferred more than people and monitor your child’s attempts at social interaction
Repetitive movements: Children with autism often exhibit what researchers and practitioners call “stereotypy.” These are repetitive or unusual movements of the body. This often can look like repetitive rocking, hand flapping, unusual stiffening or flaring of their fingers, or waving their fingers in front of their eyes

18-24 Months: Expanding Concerns

The American Academy of Pediatrics recommends that pediatric care providers screen all children for ASD at ages 18 and 24 months. Additional screening might be needed if a child is at high risk for ASD or if signs and symptoms are present.

Communication Milestones to Monitor:

Does not point to show you something interesting by 18 months of age
Limited vocabulary for age
A delay in speech alone generally does not signify autism, but in combination with other warning signs, could suggest that a toddler is at risk

Social Development Red Flags:

Does not notice when others are hurt or upset by 24 months (2 years) of age
Lack of affection: A child at risk for autism may not enjoy cuddling on a regular basis, although he may sometimes enjoy it
Difficulty with social reciprocity

Sensory and Behavioral Patterns:

Sensory sensitivities: A child at risk for autism might show unexpected reactions to certain sounds, textures, and/or tastes
Restricted eating patterns: The example of an 18-month-old who refuses to eat the cheerios or pieces of banana she has given him. Sam becomes upset when presented with the solid food so Ms. Jones eventually gives him some baby food and a bottle illustrates how feeding difficulties can be an early indicator
Unusual object play: A young child with autism may make unusual movements with objects. This can look like lining up objects in a very precise manner, spinning the wheels of a toy car instead of playing with a car, placing items in front or to the side repeatedly

Age-Specific Developmental Milestones and Autism Signs

Typical Development vs. Autism Indicators

Understanding normal developmental milestones helps parents recognize when something might be concerning. If children are autistic, early signs of autism usually appear in the first 1-2 years of life. Early signs of autism are listed below. Some children have many early signs, whereas others have only a few. The number of signs can vary according to children’s ages and stages of development. Sometimes early signs of autism change over time or become clearer as children get older.

Communication Development:

Typical development includes:

Typical social and communication development in children includes things like responding to their name, making eye contact, and using gestures

Autism indicators include:

Not consistently use eye contact to get your attention – for example, they might not always look at you and then at a snack to show you they want it, or not look back towards you when they see something that excites them

The Importance of Professional Assessment

Only a professional can determine if your child is at risk for an autism spectrum disorder. However, it is very common for typically-developing toddlers to also show some of the red flags listed below. This is why professional evaluation is crucial – to distinguish between normal developmental variations and genuine concerns.

These are signs and characteristics that babies and toddlers with autism may display, but they are by no means definitive, and their presence or absence should not be taken by parents or carers as conclusive evidence of autism or otherwise. Instead, if your baby or toddler displays some of the characteristics of autism outlined above, or is developing at a different rate to other children of their age, it is important that you get the advice of a medical professional, such as your GP, a nurse or a health worker. An autism assessment conducted by trained and qualified specialists in diagnosis will answer the question as to whether an individual is on the autism spectrum or not.

When to Seek Professional Evaluation

Red Flag Combinations

If your child is experiencing some, many, or all the signs above at 12 – 18 months, it is highly recommended to begin consulting with a medical professional and potentially scheduling a diagnostic evaluation. It’s important to look for patterns rather than isolated behaviors.

Early Screening Recommendations

The American Academy of Pediatrics (AAP), the leading pediatric health organization in the United States, recommends that all children be screened for autism at ages 18 months and 24 months, in addition to undergoing developmental and behavioral screenings during their regular well-child visits at 9 months, 18 months and 30 months.

Available Assessment Tools

Several screening tools can help identify children who may benefit from further evaluation:

M-CHAT-R: The M-CHAT-R™ (Modified Checklist for Autism in Toddlers) is a widely-used screening questionnaire
ASDetect App: If you’d like to check your child’s behaviour and development for early signs of autism, you can download ASDetect. This free, evidence-based app is developed by La Trobe University and suitable for use with children aged 11-30 months

The Critical Importance of Early Intervention

Research-Backed Benefits

The research consistently shows that early intervention can dramatically improve outcomes for children with autism. Some studies have shown that early intervention can improve a child’s IQ by an average of 17 points. More broadly, studies have also shown that children who receive early intervention services have better outcomes in communication, socialization, and behavior than those who do not receive intervention.

Research shows that early diagnosis of and interventions for autism are more likely to have major long-term positive effects on symptoms and later skills. The timing is crucial: with early intervention, some children with autism make so much progress that they are no longer on the autism spectrum when they are older.

Long-term Impact

Early intervention doesn’t just improve immediate functioning – it has lasting benefits that extend well into adulthood. Research has found that children who receive early intervention are more likely to attend regular education classes and have higher rates of employment in adulthood. They are also less likely to require support services later in life.

Brain Development and Critical Periods

Early intervention for autism means providing therapeutic services to a child with ASD, typically starting as early as two or three years old. During these early years, the brain is still rapidly developing, which is why early intervention is key to a child’s development and functioning later in life.

The research on brain development supports this approach. Recent studies have shown that people with autism have unique brain activity, structures, and connections even at very young ages. There are differences in brain growth in ASD as early as 6 months of age.

Evidence from Meta-Analyses

A comprehensive review of early intervention research found encouraging results. In total, 33 RCTs were included in the meta-analysis using the random effects model. The total sample consisted of 2581 children (age range: 12–132 months). Early interventions led to positive outcomes for cognitive ability (g = 0.32; 95% CI: 0.05, 0.58; p = 0.02), daily living skills (g = 0.35; 95% CI: 0.08, 0.63; p = 0.01), and motor skills (g = 0.39; 95% CI: 0.16, 0.62; p = 0.001).

Another meta-analysis focusing specifically on social communication found that a systematic review of the literature included 1442 children (mean age 3.55 years) across 29 studies. The overall effect size of intervention on social communication outcomes was significant (g = 0.36). The age of the participants was related to the treatment effect size on social communication outcomes, with maximum benefits occurring at age 3.81 years.

What Parents Can Do Right Now

Immediate Actions

Trust Your Instincts: Early detection and early intervention along with early ABA therapy can have a lifetime impact for children with autism so it is important to trust your gut if you feel like something is suspect
Don’t Wait: If you have any concerns about your child’s development, don’t wait. Speak to your doctor now about screening your child for autism
Document Behaviors: Keep notes about specific behaviors you’re observing, including when they occur and their frequency
Use Available Resources: The Centers for Disease Control and Prevention (CDC) Act Early program provides parents, childcare professionals and pediatric clinicians with free resources, in English and Spanish, for monitoring a child’s development. The program offers parent-friendly, research-based milestone checklists for children as young as 2 months of age. The Milestone Tracker App can help parents track their child’s development and share the information with their pediatricians

Addressing Wait Times

Unfortunately, many families face significant delays in getting evaluations. Many diagnostic clinics can have lengthy waitlists, and often children with autism do not get a formal diagnosis until closer to 2 years of age. However, an ASD diagnosis from a doctor is not necessary for a child to begin receiving services.

Supporting Your Child’s Development

While waiting for professional evaluation, parents can still support their child’s development:

Engage in interactive play
Model gestures and language
Create structured routines
Provide sensory-friendly environments when needed
Focus on building connection and communication

Addressing Common Concerns and Misconceptions

“My Child Shows Some Signs But Not Others”

These are some common characteristics of autism that may be observed in babies and young children, although it is unlikely that a child will show signs of all of them. Some signs may change over time, or become more obvious as a child gets older. Every child with autism is unique, and the presentation can vary significantly.

“Maybe They’ll Grow Out of It”

While some developmental delays can resolve on their own, autism is a lifelong condition. However, some children who receive early intervention will make so much progress that their autism symptoms and behavioral issues are drastically improved by middle to late childhood. The key is getting appropriate support as early as possible.

Gender Differences

Autism can sometimes be different in girls and boys. This means autism can be harder to spot in girls. Girls may present with more subtle signs or different behavioral patterns, making early identification more challenging but no less important.

The Role of Healthcare Providers

Pediatric Screening

The American Academy of Pediatrics recommends that pediatric care providers screen all children for ASD at ages 18 and 24 months. If your pediatrician hasn’t mentioned autism screening, don’t hesitate to bring up your concerns.

Specialist Referrals

If initial screening suggests concerns, your pediatrician may refer you to specialists such as:

Developmental pediatricians
Child psychologists
Pediatric neurologists
Early intervention programs

Creating an Action Plan

Step 1: Monitor Development

Use milestone checklists
Document specific concerns
Take videos of concerning behaviors

Step 2: Seek Professional Input

Discuss concerns with pediatrician
Request formal screening if warranted
Consider private evaluation if wait times are long

Step 3: Access Early Intervention

Each state has its own early intervention program for children from birth to age 2 years who are diagnosed with developmental delays or disabilities, including ASD. These programs are specified by Part C of Public Law 108-77: Individuals with Disabilities Education Improvement Act (2004), sometimes called “IDEA.” Some states also provide services for children who are at risk for developmental delays and disabilities

Step 4: Build Your Support Network

Connect with other families
Learn about available resources
Prepare for the journey ahead

Economic Considerations and Cost-Effectiveness

Early intervention isn’t just beneficial developmentally – it’s also economically advantageous. Late treatment is associated with lifetime costs that can be 40% higher than when intervention starts at age 2. The literature shows that, typically, the younger a child with autism spectrum disorder (ASD) is when s/he receives treatment, the better the outcomes they experience over a lifetime. These include improved adaptive functioning, decreased autism symptoms, increased intellectual functioning and developmental growth, as well as an increase in quality of life.

Conclusion: Hope Through Early Action

Recognizing early signs of autism in toddlers can feel overwhelming, but remember that early detection opens doors to intervention and support that can dramatically improve your child’s trajectory. There is no debate or doubt: early intervention is your child’s best hope for the future.

The statistics are encouraging: early diagnosis of autism can help children receive timely intervention, develop skills, manage sensory experiences, and behaviors, leading to improved quality of life both now and in the future. Early intervention can make a significant difference in the child’s life, as research shows that accessing early intervention for autism is more likely to result in positive outcomes in the future than starting intervention later in childhood or adulthood.

Research has shown that early intervention can improve a child’s overall development. Children who receive autism-appropriate education and support at key developmental stages are more likely to gain essential social skills and respond better in society. Early intervention increases a child with autism’s potential for a better life.

Remember, every child develops at their own pace, and having some of these signs doesn’t automatically mean your child has autism. However, if you notice multiple red flags persisting over time, don’t hesitate to seek professional guidance. The earlier we can identify and support children with autism, the better their outcomes will be.

Your vigilance, advocacy, and love are your child’s greatest assets. Trust your instincts, seek professional support when needed, and remember that with early intervention, children with autism can thrive and reach their full potential.

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