The characteristic behaviors of autism spectrum disorders may or may not be apparent in infancy (18 to 24 months), but usually become obvious during early childhood (24 months to 6 years).
As part of a well-baby/well-child visit, your child's doctor should do a "developmental screening," asking specific questions about your baby's progress. The National Institute of Child Health and Human Development (NICHD) lists five behaviors that signal further evaluation is warranted:
Does not babble or coo by 12 months
Does not gesture (point, wave, grasp) by 12 months
Does not say single words by 16 months
Does not say two-word phrases on his or her own by 24 months
Has any loss of any language or social skill at any age
Having any of these five "red flags" does not mean your child has autism. But because the characteristics of the disorder vary so much, a child showing these behaviors should have further evaluations by a multidisciplinary team. This team may include a neurologist, psychologist, developmental pediatrician, speech/language therapist, learning consultant, or other professionals knowledgeable about autism.