Child behaviors are those that announce the presence of the disease, and the parents are usually the ones who notice unusual events. In some cases, the baby looks different from birth: do not observe those around them, focus on an object for a long time, is very quiet and cries very often.

Signs that occur in the first year after birth:
• does not react when hearing his mother's voice
• reduced eye contact
• does not point the finger
• does not smile

Signs that occur in the second year after birth:
• does not say a word until 16 months
• does not know how to play with toys
• does not combine two words until the age of 2
• lose his speaking skills
• does not manifest interest when adults point out the object with the finger

Signs that occur in the third year after birth:
• manifests repetitive stereotypical activities (repeated opening and closing doors, rotating around its own axis, waving or looking at hands, etc.).
• avoids touching and eye contact
• repeats words or phrases
• manifest preference to a particular toy or object
• walks on tiptoe
• poor coordination

Other symptoms
Dr. Tim Buie, gastroenterologist at Harvard University and Mass General Hospital in Boston performed endoscopy to over 1,000 children diagnosed with autism. In the first 400 children he found that gastrointestinal problems are more common in children with autism than in typical ones.