Babies develop at their own pace, and many don't follow exact timelines found in some parenting books. But children with autism spectrum disorder usually show some signs of delayed development before age 2 years.

If you're concerned about your child's development or you suspect that your child may have autism spectrum disorder, discuss your concerns with your doctor. The symptoms associated with the disorder can also be linked with other developmental disorders.

Signs of autism spectrum disorder often appear early in development when there are obvious delays in language skills and social interactions. Your doctor may recommend developmental tests to identify if your child has delays in cognitive, language and social skills, if your child:

• Doesn't respond with a smile or happy expression by 6 months
• Doesn't mimic sounds or facial expressions by 9 months
• Doesn't babble or coo by 12 months
• Doesn't gesture — such as point or wave — by 14 months
• Doesn't say single words by 16 months
• Doesn't play "make-believe" or pretend by 18 months
• Doesn't say two-word phrases by 24 months
• Loses language skills or social skills at any age