What causes menstral pain?

Cramps: Cramping usually causes menstrual pain (dysmenorrhea). If severe, chronic may wish to be medically evaluated to check for causes like dysmenorrhea can be caused by polyps, fibroids & adenomyosis.

Menstrual pain: Release of prostaglandins in the uterus during menstruation cause the uterus muscles to contract, causing blood supply to the endometrium to constrict, which in turn break down & die, then be expelled as menses. These contractions & the resultant temporary oxygen deprivation to tissues, cause the cramps.