I am getting a heap of work done on my teeth and now that we are pregnant I am worried about the whitening part?

The dentist said that he is quite confident I can use to no affects? I am only about 7 weeks and will be using it for the next 2?

I read the instructions and it says not to use while BF and PG? I am really confused? I have already paid for it all and need to start as the old capping on my teeth is falling off!

Have you used Dentist grade whitening when pregnant? What should I do?