Are perms bad for you?

I was just wondering because I was thinking about getting a perm soon, and I was wondering if the chemicals in the perm effect your health. I mean I understand that any chemical is going to have at least a little harm on your body but I was just wondering if I would be prone to any diseases or anything like medical conditions that you can get. I'm a worrywart and I just really want to know. And why is it not advised for pregnant ladies to get perms? Thank you.