Is teeth whitening safe during pregnancy?

While it is likely safe, there are no studies or proof that it is safe to use during pregnancy.  If you whiten, you are using the product "off label" and risking the health of your unborn child.
You only have a few months to wait before there is zero risk, so most doctors would encourage waiting.

Although there is no evidence that whitening teeth while pregnant will affect the developing baby, it is best to postpone the whitening procedure until a woman is no longer pregnant and not breastfeeding.   Healthy babies are very important, and until we know more, we recommend choosing the safest option: waiting.  

In the meantime, it is critical to keep your gums and teeth very healthy.  Pregnancy gingivitis and periodontal disease can actually be a risk to the developing baby, so make sure to see your dentist!

There are no studies related to pregnant women and teeth whitening.  I would not recommend whitening your teeth while pregnant.  Keep risks to a minimum while pregnant.  It is not a necessity to have white teeth!  A healthy baby is what is important.