We don't have any evidence that bleaching or whitening your teeth during pregnancy poses any risks to you or your baby.
However, since there isn't enough data to tell us for sure whether it's safe, health care providers recommend that you wait until after pregnancy and breastfeeding to have your teeth bleached by the dentist or to use over-the-counter teeth bleaching or whitening products.
The carbamide peroxide in these products reacts with water to become hydrogen peroxide. This oxidation process can be harmful to tissues and cells, especially during pregnancy when your gums are more sensitive than usual. We don't know whether this is a risk to you or your baby, so it's best to hold off on using these products.
There's another whitening process you can do at home, called microabrasion, which uses acidic components to remove stains. There's even less pregnancy data on these products.
It's fine to use whitening toothpastes during pregnancy. These products contain a much lower level of bleaching agent and are not thought to be any risk during pregnancy or while breastfeeding. You can also avoid staining your teeth by not drinking coffee, tea, and dark fruit juices such as grape juice.