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Signs of Autism in Children, Babies and Toddlers

November 21, 2023

Did you know autism spectrum disorder (ASD) can be detected in babies, infants, and toddlers, yet many children on the spectrum do not receive a diagnosis until the age of two or three? Because of that, it’s crucial to understand some of the most common signs of autism in children.

This article overviews the main symptoms, characteristics, and signs of autism in children, helping more parents and caregivers get an early diagnosis for their little ones. Early intervention is the key to a healthy future for your child, so let’s learn all about it.

Signs of Autism in Children, Babies and Toddlers

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Diagnosing Children with Autism Spectrum Disorder (ASD)

The National Institute of Neurological Disorders and Stroke (NINDS) cites four major “classic” symptoms that pediatricians often use to diagnose children with autism:

However, many of the above are almost impossible to see in a small baby who is not yet in the age range of talking or developing interests. This means many parents do not seek diagnosis until a later stage, and their child might miss out on the benefits of early intervention.

So, let’s break down some of the early signs of autism parents can look out for.

The Earliest Signs of Autism in Babies

Every infant and adult with autism spectrum disorder will display unique symptoms, but several key traits may point to autism.

Lack of Physical Engagement with Parents

Autistic babies might not engage with their caretakers like neurotypical infants do. For example, a baby with autism might not respond to cooing or ignore movements such as waving and clapping.

Limited Eye Contact

A mother might notice her baby does not make eye contact while nursing. Autistic babies might have difficulty smiling or giggling. Additionally, autistic babies may be fussier and harder to console than their neurotypical peers.

Sensory Processing Challenges

Textures, bedding, and clothing (especially new fabrics) can cause distress to babies on the spectrum. They also get overwhelmed by toys that make noise or have flashing lights.

Impaired Social Interaction

Early signs of impaired social interaction may appear at six to nine months when neurotypical babies start to imitate and respond to the people around them. Babies with autism spectrum disorder will often not smile back or laugh when playing a silly game, and some may stare blankly and appear oblivious to the game. Others might even show distress at the sound of laughing. However, an upset or loud voice might not startle nor mean anything to them.

Other developmental milestones they might not meet include responding to their name. They might also not babble at six months, usually when neurotypical babies start doing so. By 18 months, most babies engage in imaginative play. Infants with autism, however, will likely show no interest or become flustered.

Signs of Autism in Toddlers

Toddlers with autism generally exhibit a progression of the symptoms expressed during infancy. Autistic toddlers may express frustration via tantrums or outbursts.

Diagnosing autism in toddler boys is markedly more common than in girls. Boys (and some girls) aged two to four often begin to show symptoms associated with autism, such as:

Poor Social Skills

Symptoms of autism are likely to become more obvious as the toddler begins to meet other kids in school or daycare and struggles with social skills.

Restricted Interests

The child might be fascinated with one or two types of toys or topics and have little interest in other play.

Sensory Issues

Sensory dysregulation is often harder for toddlers to manage as they receive intense stimuli that neurotypical children enjoy. Distressing events might include birthday parties or group outings.

Pronounced difficulty connecting with their caretakers. Issues spotted when the child was a baby will continue.

Challenging Behaviors

Aggressive or apathetic relationships with caregivers might develop. Aggression might indicate frustration, fear, or pain that the toddler attempts to communicate.

Do Signs of Autism in Children Differ in Girls and Boys?

Early signs of autism are sometimes clearer in boys than in girls. According to research, only one in four children diagnosed with autism is female. Only one girl in every nine boys is diagnosed with Asperger’s syndrome. Young children might be misdiagnosed as having social communication disorders or developmental disorders.

These girls are often labeled as having developmental delays, but without the diagnosis of autism, their access to resources and care becomes limited. The Cleveland Clinic recommends being proactive and seeing your pediatrician if you notice any signs your daughter might be autistic, especially if she is between regular medical check-ups.

When Can My Child Be Diagnosed with Autism?

According to the Center for Disease Control (CDC), an autism diagnosis can be appropriately given at 18 months or sooner. Doctors screen for autism spectrum disorders at the nine-month, 18-month, 2-year, and 3-year wellness checkups. 

Many children with autism do not receive an official diagnosis until the age of two or three. It is often after the child has started school. This is when the child’s challenges in social skills become obvious. It is never too late to get a diagnosis and identify resources to help make life with autism easier.

The earlier a child gets a diagnosis (especially in their formative years of development), the sooner they can start therapy or treatment.

Download our FREE Checklist on the Signs Of Autism

When to See Your Pediatrician

During checkups, your child’s pediatrician will assess developmental progress. In between appointments, however, you may notice signs of autism or suggestions your child is not developing similarly to their peers. They may not engage with you like other babies engage with their parents or exhibit some of the other symptoms listed above.

If you feel something is amiss, consult your child’s pediatrician to run a series of diagnostic exams. These exams are non-invasive and will often include a developmental and behavioral assessment. You might also be given a questionnaire for you and other caregivers in your child’s life.

How to Prepare for the Appointment

Some parents find it helpful to list symptoms they suspect are likely to be autism. You can keep track of the frequency of instances each behavior occurs for reference. This documentation will give your child’s pediatrician a better idea of how long and often your child’s symptoms appear.

Most infants with autism will develop skills late – or might even regress in their social skills and sensory processing.

Getting a Second Opinion

If your doctor is unsure if a diagnosis of autism is appropriate for your infant, the CDC recommends seeking a second opinion. The earliest interventions can serve as building blocks for your child’s future therapies.

They also suggest acting early as interventions can change your child’s developmental path and improve outcomes in school and relationships. The CDC cites that, in the first three years of a child’s life, his/her behaviors are most malleable and that children are more likely to change undesirable habits and adopt positive ones most willingly during these years. They suggest trying several interventions until you find one (and a therapist) your child responds to best.

Early Interventions for Autism

Once you’ve spotted the signs of autism and received an early diagnosis, you can consider the next steps.  Psychiatrists, psychologists, and occupational therapists can all help support autistic children. Here are the most popular interventions and therapies:

  • Early Start Denver Model: ESDM is a relationship-based program that encourages positive feedback, shared activities, and parental involvement.
  • Applied Behavioral Analysis: Many families use ABA, which encourages a positive reward system and parental engagement with the program.
  • Picture Exchange Communication System: PECS teaches non-verbal and semi-verbal children to communicate via pictures and symbols.
  • Verbal Behavioral Intervention: VBI is also used with children who struggle with speech, but instead of communicating with pictures, it focuses on teaching verbal communication.
  • Discrete Trial Training and Pivotal Response Training: DTT and PRT focus on behavioral and motivational challenges a toddler with autism may experience.
  • DIR/Floortime Therapy: DIR/Floortime aims to help children with ASD connect while using their interests and passions to develop engagement skills and symbolic thinking, increase logical thinking, and improve interaction.

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While autism is most often diagnosed when a young child hasn’t met popular milestones during the formative years and/or when a child’s development has suddenly regressed, some experts believe there are signs of autism that point toward a diagnosis earlier in a child’s life.

While not every person who is autistic can be diagnosed as an infant, there are many benefits to receiving a diagnosis before preschool age.

If your child is exhibiting signs of autism, even minor ones, document them and share your concerns with your child’s physician. The earlier a child with autism is diagnosed, the sooner families and specialists can work with the child using popular interventions and selected therapies.


Q: Can autism be diagnosed in infants?

A: While autism can be challenging to diagnose in infants, some early signs and red flags may be observed. However, a definitive diagnosis typically occurs around the age of two.

Q: Are all children with autism non-verbal?

A: No, not all children with autism are non-verbal. The spectrum of autism includes individuals with varying speech and language abilities.

Q: Can autism be outgrown? 

A: Autism is a lifelong condition, but early intervention and therapy can significantly improve a child’s skills and quality of life.

Q: Are vaccines linked to autism? 

A: Extensive research has debunked any link between vaccines and autism. Vaccines are safe and vital for public health.

Q: What therapies are available for children with autism? 

A: Various therapies, including speech therapy, occupational therapy, and applied behavior analysis (ABA), can benefit children with autism.

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