One in 175 children is autistic, according to a new national survey. And though most kids aren't diagnosed until they're 2 or older, studies show that some exhibit symptoms much earlier. Concerned for your own baby? Keep an eye on his behavior.

Warning signs: Your 6-month-old doesn't smile back at you or seem to enjoy interacting. He also doesn't express himself in the usual baby ways  -- by cooing when he's happy or crying when he isn't.

Your 1-year-old may show these same symptoms and also may not respond to his name, clap when you do, or point at what interests him.

If this sounds familiar, talk to your pediatrician  -- but know that these delays don't always mean autism, says Sally Ozonoff, Ph.D., professor of psychiatry at the University of California, Davis's M.I.N.D. Institute. "They may signal a less serious condition  -- a speech problem or delays that resolve themselves in time," she says.

And if it does signal autism, the good news is that kids who are diagnosed and get help very young tend to do best later on in learning to communicate, socialize, and function in mainstream classrooms.