To Dye or Not to Dye??

I've been highlighting my hair for a few years now, but I'm wondering is it safe to continue doing while pregnant? I asked my doctor. She says she does not recommend doing it until at least 20 weeks. In 20 weeks my roots will be down to my ears!!! Everything I read in the pregnancy books and on the Internet says there is no proven risk to dying your hair while pregnant, especially if you use foils like I do because little to none of the product even touch the scalp. I mean, hairdressers get pregnant and are around the chemicals their whole pregnancy. I hate to take any unnecessary risks at all when it comes to the heath of my baby, but I wish I could just get a clear answer on how safe or unsafe it really is. For now, I guess I'll try the lemon juice recipe I used to use in high school!