Pre-pregnancy, summer may have meant soaking up the sun (at least in moderation). But now you should thoroughly protect yourself from UV rays since sun exposure can cause temporary skin discolorations, called melasma -- a.k.a. the "mask of pregnancy." And not just on your face: "If you sunbathe during pregnancy, the ‘racing stripe,’ or linea nigrea, on your belly will get much darker," Dr. Harms says. "The protection offered by sunblock will minimize discoloration."