My 18mo has quite a large birthmark at the bottom of his spine. It is usually quite pale in colour, but recently I've noticed that it goes bright red sometimes? This evening half of it is really red and looks a bit like a it might have changed shape. I think I will take him to the doctor just to be on the safe side, but in the meantime (because I am a worrier and am now a bit panicked about it!), does this sound normal? Is it something which happens to birthmarks? I don't have any so I've never paid any attention to them before DS!