The concern about hair coloring or permanents during pregnancy is that the chemical solutions used can be absorbed through the scalp into the bloodstream. Although the research that has been done to date has not shown a relationship between these chemical substances and birth defects, the effects of these chemicals during pregnancy is not known. Even if only highlighting is done, it would be tricky for the hairdresser to not allow any of the dye to touch the scalp. And although the risk to a developing baby is the greatest in the first trimester of embryonic development, we do not know what other effects chemical substances may have during the second or third trimester. I would suggest that you ask your hairdresser about natural vegetable hair-coloring products, or enjoy your own natural color for the months of your pregnancy. A special trip to the salon for hair color and styling can be your treat to yourself after the baby is born!