There's no known cause of Autism. Research suggests that Autism develops from a combination of genetic and non-genetic, or environmental, influences. These influences appear to increase the risk that a child will develop Autism.
A diagnosis of ASD is ultimately made based on your description of your child's development, plus careful observation of certain behaviours by your pediatrician, autism experts, medical tests, and your child's history.
Start by being patient and kind with yourself, your spouse, and your child. Talk to a therapist and start early intervention. Join a support group. Do research and get information on how you can support your child even at home. Find out the best programs and other resources in your area. You aren’t expected to face this challenge alone.