Autism is genetic. My DD is autistic and autistic traits can be easily traced through my immediate and extended family through every generation in living memory.
My DD is not damaged she is literally a genius and the most fabulous teenager who doesn't follow the crowd and we have the most interesting discussion. How her brain works regularly has me awe struck and has been commented on positively by every teacher she's ever had. No, she doesn't like loud noises or certain textures, yes, we have to plan our time carefully to ensure she doesn't get overwhelmed.
No she doesn't have additional learning needs, challenging behaviour or high support needs that can make parenting children with autism and other conditions very difficult
Yes, I did have additional fortnightly scans, for her head growth pattern - a pattern that is in early research stages but has been identified as an early biomarker.
Stop panicking your child is fine whether autistic or not, if they are autistic it has nothing to do with the ultrasounds and everything to do with you and his father's DNA.