The clinical term for dysmenorrhea is pain in the lower abdomen that occurs before and after menstruation and during menstruation, and is called dysmenorrhea. Pain in the stomach before menstruation is also a manifestation of dysmenorrhea and is included in the range of dysmenorrhea. Dysmenorrhea is often caused by the following: first, primary dysmenorrhea, such as pain caused by contractions of the uterus during menstruation due to sensitivity to prostaglandins. The second is secondary dysmenorrhea, which is often caused by a disease, such as endometriosis, and can get progressively worse. Third, inflammatory diseases of the pelvis can also cause dysmenorrhea, such as chronic inflammation of the pelvis, which can lead to dysmenorrhea and the usual lower abdominal pain. Fourth, due to malformation of the uterus, such as longitudinal uterus or unicornuate uterus, there may also be pain in the stomach before menstruation. Therefore, it is recommended to check, identify the cause and give treatment if necessary.