Personally, I was not willing to risk a possible negative outcome for my baby, so I lived with a god-awful two-tone look for over a year until I was finally able to cut it all out and go natural. I don't love my natural color, and would like to color it again, but our little people are already exposed to so much toxicity from the environment, that I would hate for this one act to tip the scales in the wrong direction. That's just my 2 cents. You can look up the ingredients of the hair colorant you are considering on this website:
www.cosmeticsinfo.org
You might find that even the less toxic products are still fairly toxic. Anything that touches your skin can and will be partially absorbed -- that goes for make-up, shampoo, conditioner, lotion, sunscreen, etc. When you color your hair, you get a double-whammy, because you also inhale the product. Proceed with caution.
If you do go a ahead with it, don't fret, just enjoy the heck out of it. Look fabulous!