You may gradually begin to notice the area around your nipples (the areolas) darkening and even possibly getting bigger around in diameter. Besides pregnancy, darkening of the areolas can be caused from tanning, as well as a hormonal imbalance. Sometimes early in pregnancy, women experience their Montgomery’s tubercles (glands or little bumps surrounding the nipples) begin to elevate and enlarge, becoming more prominent throughout pregnancy. This can happen around the time you would normally expect your period to begin, although some women don’t notice any difference, or sometimes not until later in pregnancy.