Autism is caused by autistics. Why? Because that's how autism spreads. See, some autistics have problems with eye contact. That's because their eyes emit a radiation called "autism rays" so that whenever they make eye contact, the invisible autism rays will come from their eyes and hit the others', thus causing the other to change until they have autism as well. The new autistic then starts to emit the same autism rays from their eyes and the cycle continues.
When this happens to a pregnant mother, the baby also gets it.