A new study out of Perth, Australia claims that there is a link between sun exposure and autism. Researchers from the Telethon Kids Institute claim to have found that pregnant rats deprived of Vitamin D showed indications of autistic behavior.
So essentially, pregnant humans have never been studied for such claims.
Even if it were true, the modern world views the sun as a big evil orange bulb that kills and mames. Chemical sunblocks are more prevelant than sandles during the warmer months.