Is there any known correlation between the presence of a choroid plexus cyst at mid-pregnancy and autism?

My son had a choroid plexus cyst at 18 weeks of gestation. I had an amniocentesis done to check if he had trisomy 18, but the result turned out to be negative. However, he's now 3 years old and was recently diagnosed with mild high functioning autism.

Also, my baby girl who's now 15 months old had a choroid plexus cyst at 18 weeks of gestation too. She's actually hitting all of her milestones on time, BUT when she was 3 or 4 months old, she had occasionally this really weird behavior of turning her head back and forth as if she was saying "no!" for sometimes 30 seconds at a time. She stopped doing that now, but she sometimes flaps her hands. She sees her brother do that too, so I'm thinking maybe she thinks that this is something cool to do. Is there any reason to worry and have her checked, though? (considering also the fact that she had a choroid plexus cyst at 18 weeks of gestation as well)

I don't think there is any (not proven) connection between a choroid plexus cyst and autism. At the moment the research suggests that autism is more due to hereditary factors than any thing else. Does any one else in your family suffer from autism?

At this point there's no known connection to much of anything. There are family histories of autism, and there have been a few studies that show a possible link between things like caffiene use or other environmental effects and pregnancy, but nothing has really been proven to cause autism. Sorry.