I'm thinking I'll go in at 27 weeks for coloring. Personally I would wait until all the vital organs and growth has occurred, maybe sometime mid 2nd trimester? Anything to keep the solution from siting on the scalp seems logical so there isn't much chance for absorption (like foils). I normally regularly color, but after reading so much controversial info I choice to wait. What color is your hair? You might temporarily try henna or henna plus indigo (completely safe). I did this twice so far just to touch up--but it's messy. PM me if you need product info.
if you would like to colour your hair you should use one with out amonia. have fun with your new colour. but you should wait until your 2nd stage it's just better.
Ok, I am a hairstylist and I work with the hair coloring, bleach, you name it. I have had two healthy little boys and I worked while pregnant breathing in the fumes. The hair color is fine, if your body was absorbing it you would be getting sick! Your scalp does not absorb the color, the only thing is the fumes may make you nausous just like everything else in the world can.. Just don't put the bowl over your face and breathe in...HAHAAHAHAH. But really it's fine.
I didn't get my hair colored all throughout my pregnancies however i would think that pulling your hair through a cap or putting foils on would be better because the dye doesn't sit on your head. It's probabley not that great to inhale the smell either( I know that's not what you wanted to hear but I'm sure you're glowing skin will make up for the roots!!)
When I was in my 1st trimester, I held off getting my hair colored but when I entered my 2nd one, the dr gave the okay to have it done. I started off just doing my roots since I still had highlights. I recently had my highlights redone w/my dr's permission. I don't know what the difference between the dye in a salon and dye in a store bought kit however. Good luck!