Being a pasty skinned Irish girl I read a bit about this last time I was pregnant.
One of the things to watch out for is streaking. Just because a product worked no problem for you pre-pregnancy doesn't mean it will be good now. Pregnant skin reacts differently than before. You could find that you have patches that are paler/darker than the rest.
Its a bit like if you do go out in the sun and get a tan - the pigment reacts differently to the sun now and you could end up with uneven tan. This is why people are advised to keep out of the sun (or use sun screen)during pregnancy, more so than other times. This can cause "pregnancy mask".