I have noticed that my some of the women I know who got pregnant have discoloration on their necks and underarms.

This change on a pregnant woman's body makes me a little uncomfortable because I'm not sure how long will the discoloration last.

Is it safe to use whitening creams and toners to remedy the discoloration especially if you're still breastfeeding?

I hope you can help me understand this change so I can feel better about these "changes" in a woman's body.