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Diagnosing autism spectrum disorder (ASD) can be difficult because there is no medical test, like a blood test, to diagnose the disorder. Doctors look at the child’s developmental history and behavior to make a diagnosis.

ASD can sometimes be detected at 18 months or younger. By age 2, a diagnosis by an experienced professional can be considered very reliable [1]. However, many children do not receive a final diagnosis until much older. Some people are not diagnosed until they are adolescents or adults. This delay means that children with ASD might not get the early help they need.

Early signs of ASD can include, but are not limited to

• Avoiding eye contact,
• Having little interest in other children or caretakers,
• Limited display of language (for example, having fewer words than peers or difficulty with use of words for communication), or
• Getting upset by minor changes in routine.

CDC’s “Learn the Signs. Act Early.” program provides free resources to help families monitor developmental milestones and recognize signs of developmental concerns, including ASD.

As children with ASD become adolescents and young adults, they might have difficulties developing and maintaining friendships, communicating with peers and adults, or understanding what behaviors are expected in school or on the job. They may also come to the attention of healthcare providers because they have co-occurring conditions such as attention-deficit/hyperactivity disorder, obsessive compulsive disorder, anxiety or depression, or conduct disorder.

Monitoring, screening, evaluating, and diagnosing children with ASD as early as possible is important to make sure children receive the services and supports they need to reach their full potential [2]. There are several steps in this process.

Developmental monitoring observes how your child grows and changes over time and whether your child meets the typical developmental milestones in playing, learning, speaking, behaving, and moving. Parents, grandparents, early childhood providers, and other caregivers can participate in developmental monitoring. You can use a brief checklist of milestones to see how your child is developing. If you notice that your child is not meeting milestones, talk with your doctor or nurse about your concerns.

When you take your child to a well visit, your doctor or nurse will also do developmental monitoring. The doctor or nurse might ask you questions about your child’s development or will talk and play with your child to see if he or she is developing and meeting milestones. A missed milestone could be a sign of a problem, so the doctor or another specialist will take a closer look by using a more thorough test or exam.

Your childcare provider can also be a valuable source of information on how your child develops. More information on developmental monitoring for early childhood educators.

Developmental screening takes a closer look at how your child is developing. Your child will get a brief test, or you will complete a questionnaire about your child. The tools used for developmental and behavioral screening are formal questionnaires or checklists based on research that ask questions about a child’s development, including language, movement, thinking, behavior, and emotions. Developmental screening can be done by a doctor or nurse, but also by other professionals in healthcare, community, or school settings.

Developmental screening is more formal than developmental monitoring and normally done less often than developmental monitoring. Your child should be screened if you or your doctor have a concern. However, developmental screening is a regular part of some of the well-child visits for all children even if there is not a known concern.

The American Academy of Pediatrics (AAP) recommends developmental and behavioral screening for all children during regular well-child visits at these ages:

• 9 months
• 18 months
• 30 months

In addition, AAP recommends that all children be screened specifically for ASD during regular well-child doctor visits at:

• 18 months
• 24 months
• Additional screening might be needed if a child is at high risk for ASD (e.g., having a sister, brother or other family member with an ASD) or if behaviors sometimes associated with ASD are present.

If your child is at higher risk for developmental problems due to preterm birth, low birthweight, environmental risks like lead exposure, or other factors, your healthcare provider may also discuss additional screening. If a child has an existing long-lasting health problem or a diagnosed condition, the child should have developmental monitoring and screening in all areas of development, just like those without special healthcare needs.

If your child’s healthcare provider does not periodically check your child with a developmental screening test, you can ask that it be done.

A brief test using a screening tool does not provide a diagnosis, but it indicates if a child is on the right development track or if a specialist should take a closer look. If the screening tool identifies an area of concern, a formal developmental evaluation may be needed. This formal evaluation is a more in-depth look at a child’s development, usually done by a trained specialist, such as a developmental pediatrician, child psychologist, speech-language pathologist, occupational therapist, or other specialist. The specialist may observe the child, give the child a structured test, ask the parents or caregivers questions, or ask them to fill out questionnaires. The results of this formal evaluation determines whether a child needs special treatments or early intervention services or both.

View and print a fact sheet on developmental monitoring and screening pdf icon[287 KB, 2 Pages, Print Only]

1. Lord C, Risi S, DiLavore PS, Shulman C, Thurm A, Pickles A. Autism from 2 to 9 years of age. Arch Gen Psychiatry. 2006 Jun;63(6):694-701.
2. Hyman SL, Levey SE, Myers SM, Council on Children with Disabilities, Section on Developmental and Behavioral Pediatrics. Identification, Evaluation, and Management of Children With Autism Spectrum Disorder. Peditarics. 2020 Jan;145(1).

Page last reviewed:  March 13, 2020Content source: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and PreventionhomeASD Homepage

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