I've done some research and there is nothing definitive out there, either way. In the packet of info my OB sent me, they said it's safe as long as it's done in a well-ventilated area.
My aunt, who has been a stylist for 20+ years, said she colors hair for pregnant clients all the time. She also colored her own hair throughout all 3 of her pregnancies.
I still don't know how I feel about it. I think I feel more comfortable about doing highlights as opposed to all over color.
What's your opinion?