i found this info on the net
THE REASON WHY YOU SHOULD AVOID HAIR DYING DURING PREGNANCY IS because of all the hormones the condition of your hair often changes (for good or bad depending on the individual) and the end result may not be the colour you were after, dying your hair has not shown any harm to unborn babies.
I'm half way through my hairdressing qualification. You can have your hair coloured during your pregnancy, most good hairdressers will insist on a skin test 24 -48 hours before you have the colour to check you don't have a reaction (this is because your hormones in your skin and hair change during pregnancy), some hairdressers will not do this test but I would highly recommend it and if you have a reaction don't have it done. Most good hairdressers will also do a strand test (they take a few strands of hair and place it in the colour they'll be using this is to check for any side effects and to see if the colour takes correctly) Some hairdressers will also not do it at all just because of the possible risks. No one knows for sure if it's safe to have your hair coloured but that also means that it's not been proven to harm the baby.
I'll be working with hair colour every day when I go back to college in September and I'm 26 weeks pregnant.
If you were just having foil highlights as they aren't going directly onto your scalp then you should be fine just make sure the room is well ventilated if you do go ahead
If you do decide to do your hair at home I use nice and easy, which is nice, just look for a colour with a low strength peroxide.
all seems ok!