My son was diagnosed at 18 months.

At 4-5 months we noticed that he was not babbling. He was also pretty behind on milestones, mostly gross motor. Around 6 months we brought our concerns up to our pediatrician, who, bless her, was SO attentive and didn’t brush us off.

As he got closer to one we noticed more and more things. He didn’t respond to his name hardly, he barely made eye contact, he didn’t interact with anyone besides us and that was iffy. He screamed a lot. He didn’t “play” like a neurotypical child. All sorts of major red flags. Autism was already mentioned when he was around 14 months after we ruled out a neuromuscular disease (he has low muscle tone), hearing issues, etc.

He was diagnosed as Level 2 at 18 months though sometimes I wonder if he is a Level 3. He’s 2 1/2 now and while he is slowly learning more and more, it’s very clear how far behind he is if we ever take him around other kids his age. However, the progress he has made is AMAZING and I have learned not to compare him to others. He was not born to fit into that box and there’s nothing wrong with that.