And does a normal child, who reacts at the age of six months, laughs, has very meaningful eye-contact, plays and is full of energy, get autism and lose all of that?
The answer a dr will give you is around age 2. there are milestones to look for and things that may raise a red flag, here are some: if your baby doesn't like being around people, plays alone and prefers to be alone rather than with people including family, if he doesn't smile or laugh if he doesnt reach for you when you go to pick him up, if he doesn't respond to his name when called not babbling or speaking more than a word a 18months At 6 months he should be rolling over or tyring to and attempting to crawl or beginnning to..not all mean autistic if he doesnt . Keep in mind there are mild cases of Autism and highly functioning kids with Autism known as Aspbergers syndrom. At 6 months its probably too early to detect but some signs may begin to be visable, I wouldn' t worry until the doctor is worried.
The symptoms of autism are always present. most people do not recognize the early symptoms, as young babies are not doing as much as toddlers. most people begin to notice there may be an issue with their child's development around 18 months. This is when children begin to speak words, are typically walking, have brief "play" encounters with other children, etc. Missing milestones is more apparent at this age, and as the child grows, than at 6 months, 9 months, etc.
I have a cousin with autism. I remember him always being a bit different from other babies. He would laugh, give eye contact, etc. I specifically remember an instance of pushing him on a swing when he was around 9 mo, he was laughing however, he did not develop cognitively/physically as other children the same age. He hit most of his milestones(sitting up, crawling) later than average.
The best thing to do is to let your the doctor know that you are concerned and he or she will explain to you symptoms of autism. they can tell right away. I have a nephew and a niece (brother and sister), and they are both have autism. I was also concerned for my 2 year old and I asked her pediatric if that was something I should worry about. Her pediatric right away told me that she is not. but I still asked the her vaccines be separated. Instead of giving her 6 shots at one time, my daughter was given 2 to 3 shots at a time, then do the rest the following month. just to be in the safe side.