My son has autism. Will his younger siblings have autism, too?
Because younger siblings of children already diagnosed with
autism spectrum disorder (ASD) have a much higher risk for also having ASD, parents and pediatricians are encouraged to carefully watch for developmental concerns, especially delays in social and language skills.
Screening tests should be used at the 18- and 24-month well-child checkups to target skills that are typically deficient in children with autism.
More importantly, parents, caregivers, and pediatricians are encouraged to watch for
early signs of ASD during the first 2 years of life. Parents should report any concerns to their child's pediatrician. In addition to delays in joint attention, gestures, and speech, parents should tell the pediatrician if the younger child has:
No babbling by 12 months
No pointing or other gesturing by 12 months
No single words by 16 months
No 2-word phrases by 24 months
Loss of any language or social skills at any age
There could be many reasons besides ASD for why a child may fail to perform these skills, but talk to you pediatrician. A child with any of these signs should be fully evaluated for autism and other developmental disorders.
Source: Understanding Autism Spectrum Disorders (Copyright © 2015 American Academy of Pediatrics)