This is a personal decision that only you can make. Realistically, it is best to avoid hair dye as much as possible. In a perfect world, it's best to reduce all unnecessary chemical exposures during pregnancy and breastfeeding (for your health and the health of your baby). However, oftentimes this is unrealistic. If you choose to dye your hair while pregnant, it's recommended to wait until after the first trimester (when the fetus undergoes the most rapid development) and to opt for natural henna.