Breast pain before menstruation is not very different from breast pain of pregnancy. The nature of the pain is basically similar, but the timing of the pain is slightly different. Generally, if breast pain is caused by increased levels of progesterone before menstruation, it occurs mostly 1 week before menstruation. Because this is the time when progesterone levels are at their highest, progesterone stimulates the breast glands and a physiological enlargement of the breast occurs, resulting in breast pain. Most of the breast pain lasts for 1 week, and after 1 week the patient will have her period. After her period, the patient’s breast pain will disappear because the estrogen and progesterone levels will decrease. If the breast pain persists after menstruation, the pain is not simply caused by a period, but by a breast lesion. In general breast pain caused after pregnancy occurs mostly 3-5 days after the fertilized egg is laid, so it is related to the time when the fertilized egg is laid. In most cases, breast pain occurs at the beginning of the next upcoming period, so the timing of the pain varies. Moreover, breast pain after pregnancy is mostly accompanied by delayed menstruation, which occurs throughout the period of delayed menstruation.