The phenomenon of severe stomach pain during menstruation and natural disappearance after menstruation is called dysmenorrhea. Dysmenorrhea mostly occurs during menstruation, and some people occur a few days before menstruation. Abdominal pain is aggravated after menstrual cramps, and everything is normal after menstruation. The characteristics of abdominal pain are closely related to menstruation, and there will be no abdominal pain without menstruation. So abdominal pain unrelated to menstruation is not dysmenorrhea. Dysmenorrhea can be divided into primary dysmenorrhea and secondary dysmenorrhea. Primary dysmenorrhea refers to abdominal pain at the beginning of menstruation, while secondary dysmenorrhea refers to menstrual abdominal pain after several years or more. The causes of the two kinds of dysmenorrhea are different. The causes of primary dysmenorrhea are uterine stenosis, uterine dysplasia or large endometrium in menstrual blood. The latter condition is called membranous dysmenorrhea.