What advice should I give a parent of a 12‑month‑old infant who is concerned about autism because a family member has autism?

Screening for Autism Should Begin at 18-24 Months, Not at 12 Months

The correct advice is Option A: Screening for autism starts at 18-24 months. At 12 months of age, formal autism-specific screening is premature, but this child warrants intensified developmental surveillance given the family history.

Why 18-24 Months is the Standard Screening Age

• Population screening at 18-24 months is the evidence-based recommendation from the American Academy of Pediatrics for all children, with tools like the M-CHAT demonstrating optimal performance in this age range 1, 2.

• Screening before 18 months has significant limitations: Studies show that screening at 14-15 months yields very low case detection rates (<1 in 1000) and poor positive predictive value (only 0.25), meaning most children flagged would not have autism 1.

• Autism symptoms emerge gradually across the first 24 months of life, making earlier screening less sensitive due to higher false-negative rates 1.

• Most children with ASD show clear signs by 18-24 months, though parents often report concerns earlier 3.

This Child Requires Intensified Surveillance Due to Family History

Because this child has a relative with autism, they are at elevated risk and need more than routine care:

• Siblings of children with ASD have a recurrence risk of 7-18%, vastly exceeding the general population risk of approximately 1.7% 1, 2, 4.

• High-risk siblings demonstrate significant deficits in social communication, cognitive functioning, and elevated ASD symptoms compared to low-risk children 1.

• At minimum, this child should receive continuous developmental surveillance at every well-child visit and be screened for ASD at both 18 and 24 months 1.

What to Do Now at 12 Months

While formal autism screening is not yet indicated, you should:

• Conduct enhanced developmental surveillance at this visit and all subsequent visits, specifically monitoring for early red flags 1, 2.

• Educate the parent about early warning signs to watch for, including:

  • Reduced eye contact and diminished response to name 3
  • Limited or absent joint attention behaviors (inability to share focus about objects) 3
  • Decreased use of gestures like pointing or waving 3
  • Repetitive actions or unusual sensory interests 3

• Take parent concerns seriously: By 12 months, parents of high-risk children who later develop autism report significantly more concerns in ASD-related areas, and these concerns predict diagnostic outcomes 5, 6.

• Concerns about sensory behavior and motor development can predict ASD as early as 6 months in high-risk children, while social communication concerns typically emerge after 12 months 6.

Common Pitfalls to Avoid

• Do not simply reassure and dismiss the concern without establishing a surveillance plan—this child's family history mandates closer monitoring 1.

• Do not wait for language delay as the primary indicator, as social communication differences often appear earlier 3.

• Do not delay evaluation with "wait and see" if concerning signs emerge before 18 months—early identification enables timely intervention with significantly improved outcomes 7, 2.

• If the parent reports specific developmental concerns today (beyond general worry about family history), consider broadband developmental screening tools now, as autism can sometimes be detected by the first birthday using tools like the CSBS DP Infant/Toddler Checklist 1.

The Bottom Line

Schedule formal autism-specific screening at 18 and 24 months 1, 2, but implement intensified developmental surveillance starting now given the elevated familial risk. Document the family history prominently and ensure close follow-up at every well-child visit.