There is little difference between premenstrual breast pain and pregnancy breast pain, but the timing of the pain makes a difference. 1. Premenstrual chest pain: probably in the week before menstruation progesterone levels rise, which can irritate the mammary glands and cause breast pain. Breast pain is usually for about a week, and the estrogen level will drop when your period comes and the pain will go away. 2. Pregnancy chest pain: chest pain in pregnancy is mainly due to the placenta secretes a large amount of estrogen and progesterone to stimulate the development of the mammary glands, resulting in breast pain during pregnancy. This pain is related to the time of the fertilized egg’s implantation. When breast pain occurs, in addition to menstruation and pregnancy, it may also be caused by other factors, it is recommended to visit the hospital in time for examination, to clarify the cause of the disease, and then follow the doctor’s instructions to deal with the treatment.