Stepping out of response order to say to bumblebeebuzzy
You can't prevent autism in pregnancy, but I guess you reduce your chances of having an autistic child if you are NT, your partner is NT, and everyone in your family is NT. Plus if you don't have a prem baby, a baby with a genetic condition, learning disabilities etc. But that is largely beyond our control, thank heavens.
There have been studies looking into attempting to reduce likelihood of autism. Autism Speaks in America used to fund a lot of research, and in the UK we had the PACT research about 10 years ago which attempted to reduce "severity of symptoms" initially but has morphed into a way of (benignly) increasing communication attunement between parents and autistic children.
There have always been programmes such as ABA and son-rise (now renamed but I can't recall new name) that have made claims about reducing autism "symptoms".
However, nowadays, there are more people - particularly autistic people - saying that such approaches as ABA are dehumanising at worst, and just encourage better masking at best, and that it's ok to be autistic. My view is that some small aspects of ABA, such as PECS, used kindly and with clear purpose, can be a way to help autistic children who otherwise have no way of being predictably understood to have a way to express their needs; but I am not in favour generally of extinguishing behaviours etc unless these are harmful to the youngster or dangerous.
I appreciate that autism is a vast spectrum and that caring for youngsters who will need life long 24 hour care is not something that most people who embark on parenthood would have in their vision and expectation list. But just like everyone else, autistic people vary enormously in their talents, passions, roles, and lives. Imagine if we had stamped out autism hundreds of years ago - no Mozart, no Newton, no Emily Dickinson, no Einstein, no Tesla, no Bill Gates, no Pokémon.....
I would not change my autistic children (though I might make my son magically less avoidant of showering!). They deserve life, they are valid and wonderful and loved.