Babies develop at their own pace, and many don't follow exact timelines found in some parenting books. But children with autism usually show some signs of delayed development by 18 months. If you suspect that your child may have autism, discuss your concerns with your doctor. The earlier treatment begins, the more effective it will be.
Your doctor may recommend further evaluation if your child :
· Doesn't babble or coo by 12 months
· Doesn't gesture such as point or wave by 12 months
· Doesn't say single words by 16 months
· Doesn't say two-word phrases by 24 months
· Loses previously acquired language or social skills at any age
Tests and Diagnosis of Autism
Your child's doctor will look for signs of developmental delays at regular checkups. If your child shows some signs of autism, you may be referred to a specialist in treating children with autism. This specialist, working with a team of professionals, can perform a formal evaluation for the disorder.
Because autism varies widely in severity and manifestations, making a diagnosis may be difficult. There isn't a specific medical test to pinpoint the disorder. Instead, a formal evaluation consists of an expert observing your child and talking to you about how your child's social skills, language skills and behavior have developed and changed over time. To help reach a diagnosis, your child may undergo a number of developmental tests covering speech, language and psychological issues.
Although the signs of autism often appear by 18 months, the diagnosis sometimes isn't made until age 2 or 3, when there may be more obvious delays in language development and social interactions. Early diagnosis is important because early intervention preferably before age 3 seems to be associated with the best chance for significant improvement.
The above information thankfully comes from the Mayo Clinic.com at the following link.