Children with autism typically experience developmental delays, but not every child with a developmental delay has autism. Other factors, such as problems with hearing or vision, can also cause or contribute to developmental delays.

Developmental milestones are markers that help determine whether a child is developing at a typical rate compared with other children of the same age.

When a child does not reach a certain milestone, healthcare professionals refer to this as a developmental delay. Many factors can cause or contribute to this type of delay.

This article compares developmental delays and autism, including tips on detecting each one and how to support a child in either case.

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According to a 2023 report from the Centers for Disease Control and Prevention (CDC), about 8.5% of children ages 3–17 years in the United States have a diagnosis of any developmental disability, including autism spectrum disorder (ASD).

The same report notes that about 6% of children in this age range have a diagnosis of “other developmental delay,” which describes a developmental delay that is neither an intellectual disability nor ASD.

Children with ASD typically show developmental delays in one or more areas. However, not every child who experiences a developmental delay has autism.

Developmental delays can also result from underlying health issues such as:

  • hearing problems, which may contribute to delays in language and communication
  • vision problems, which may contribute to delays in motor development
  • certain genetic or metabolic conditions, which may cause delays in multiple areas

If a child has significant delays or delays in multiple areas may indicate ASD.

Developmental milestones are markers of a child’s development from infancy to early childhood. They help determine whether a child is developing at a typical rate for their age.

These milestones may include:

  • social and emotional skills
  • language and communication skills
  • cognitive skills such as thinking, learning, and problem-solving
  • physical skills

The following table outlines some examples of milestones at various ages, according to the CDC.

AgeSocial and emotional milestonesLanguage and communication milestonesCognitive milestonesPhysical milestones
2 monthslooks at a caregiver’s face
reacts to loud noiseswatches a caregiver when they moveholds their head up when lying on their tummy
6 monthsshows awareness of familiar peopletakes turns making sounds with a caregiverreaches for toysuses their hands for support when sitting
1 yearplays games with a caregiver, such as pat-a-cakewaves goodbyeputs items in a containerwalks while holding on to furniture
18 monthspoints to show items of interesttries to say three or more words besides “mama” or “dada”copies a caregiver performing choreswalks without assistance
2 yearslooks at a caregiver’s face to see how to react in a new situationsays at least two words togethertries to use switches, knobs, or buttons on toyskicks a ball
3 yearsnotices and plays with other childrenasks “who,” “what,” “where,” or “why” questionsdraws a circle when a caregiver shows howputs on some clothes without help
5 yearsfollows rules or takes turns when playing with other childrenuses or recognizes simple rhymescounts to 10hops on one foot

The CDC provides a checklist for caregivers to help determine whether a child is reaching certain milestones, as well as a milestone tracker app, which offers an illustrated checklist and information on what to do if a child does not reach a milestone.

Children with ASD often show differences in the following areas compared to peers without ASD.

Social communication and interaction

Some characteristics of social communication and interaction may have an association with ASD, and some of these may become clear at certain developmental milestones. However, they do not always indicate ASD.

The table below shows some characteristics that may indicate ASD, according to age.

AgeSocial communication and interaction characteristics that may indicate ASD
all agesavoids or does not maintain eye contact
by 9 monthsdoes not respond to name
by 12 monthsuses few or no gestures
by 18 monthsdoes not point to show something interesting
by 2 yearsdoes not notice when others are hurt or upset
by 3 yearsdoes not notice other children or join them in play
by 5 yearsdoes not sing, dance, or act for a caregiver

Restricted or repetitive behaviors or interests

People with ASD may have behaviors or interests that seem unusual to those without ASD. These can be a bigger indicator of ASD than differences in social communication and interaction alone. Examples include:

  • lining up toys and other objects and becoming upset when they are not in order
  • playing with toys the same way every time
  • becoming upset by minor changes
  • developing obsessive interests
  • repeating words or phrases over and over
  • repetitive movements, such as:
    • flapping their hands
    • rocking their body
    • spinning in circles

Other characteristics

Other characteristics that are common among people with ASD include:

  • showing hyperactive, impulsive, or inattentive behavior
  • having unusual eating and sleeping habits
  • having unusual mood or emotional reactions
  • experiencing anxiety, stress, or excessive worry
  • being overly fearful or less fearful than expected

Certain medical conditions, such as seizure disorders and gastrointestinal issues, may also occur among people with ASD.

Parents or caregivers who notice developmental delays in a child should speak with a doctor or pediatrician, who can determine the cause.

Diagnosing ASD can be difficult because there is no standard test. Instead, doctors will rely on the child’s developmental history and behavior. They may wait until a child is 2 years old to make a more reliable diagnosis.

Some children may not receive a formal diagnosis until they are much older, which can prevent them from accessing early assistance that they may need to reach their full potential.

Below are some tools doctors may use to help diagnose ASD in children.

Developmental monitoring

Developmental monitoring involves observing and interacting with a child to find out whether they are meeting developmental milestones. Any caregiver can do this.

The CDC provides a milestone tracker app to help caregivers work together to monitor a child’s development.

Developmental screening

Developmental screening is a more formal process that uses research-led questionnaires and checklists to compare a child’s development with that of other children of the same age.

The American Academy of Pediatrics recommends routine developmental screening at 9, 18, and 30 months of age and specific screening for ASD at 18 and 24 months.

Children at high risk of ASD, such as those who have a family member with ASD, may need additional screening.

Developmental evaluation

A formal evaluation is necessary to diagnose ASD and may involve the following:

  • observing the child
  • having the child complete a structured test
  • having caregivers fill out questionnaires

The results can highlight the child’s strengths and challenges. They can also help healthcare professionals decide whether a child meets the criteria for a diagnosis or needs early intervention services.

Can doctors misdiagnose autism as a developmental delay?

Identifying ASD can be challenging because there is no single diagnostic tool.

Doctors base a diagnosis on observations of the child’s behavior and reports of the child’s cognitive functioning. They match these to criteria in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders.

ASD symptoms and their severity can vary from person to person and throughout a person’s life, and this can further complicate the diagnostic process.

Additionally, ASD may occur alongside other medical conditions that can contribute to developmental delays.

With this in mind, it is possible for doctors to misdiagnose ASD as a developmental delay.

Below are some things you can do to support a child with developmental delays or ASD.

Supporting a child with developmental delay

The CDC lists resources that can help promote your child’s development, including:

  • Talking is teaching: Talk, read, sing: a public awareness and action campaign that outlines simple activities you can use to help boost your child’s early cognitive and vocabulary skills
  • Vroom: a global program offering science-based tips and tools to help support your child’s early development
  • Zero to three: a non-profit organization that provides science-based information and tools to help you support your child’s development up to the age of 3 years

Supporting a child with autism

The United Kingdom’s National Health Service provides the following tips that may help you support your child day to day:

  • Use your child’s name to get their attention.
  • Use simple language.
  • Speak slowly and clearly.
  • Use communication aids to help convey what you are saying, such as:
    • eye contact
    • gestures
    • pictures or symbols
  • Allow extra time for your child to understand what you say to them.
  • Try other communication tools, such as:
  • Seek additional help from a speech and language therapist.

A caregiver should speak with a doctor if their child seems to be experiencing a developmental delay at any age. A doctor can conduct an evaluation to identify any underlying causes and recommend supportive services if necessary.

Early intervention for developmental delay can help a child reach their full potential.

Developmental delays happen when a child does not reach certain milestones, which are markers of typical development among children of the same age. Sometimes, these delays can indicate autism.

Hearing or vision problems and other underlying medical conditions can also cause or contribute to developmental delays.

Anyone who is concerned that their child is not meeting developmental milestones can talk with a healthcare professional, who can determine the cause and arrange for additional support if necessary.