According to Mayo Clinic, cramps develop during a woman's menstrual period when the uterus contracts to shed its lining. Hormone-like substances called prostaglandins trigger these contractions, and women with higher levels of prostaglandins tend to have stronger menstrual cramps. Menstrual cramps can also develop due to multiple health conditions, including endometriosis, uterine fibroids, pelvic inflammatory disease, cervical stenosis or adenomyosis.
Each month, the inner lining of a female's uterus builds up as it prepares for a possible pregnancy. If a pregnancy does not occur, the uterus lining is not needed, and it begins to shed. According to MedicineNet, as the unneeded uterine lining starts to break down, the muscles in the uterus contract, which restricts blood flow to the uterine lining. This lack of oxygen causes the tissues of the lining to completely break down and die, and these dead tissues pass through the cervix and are expelled out of the body through the vagina. Chemicals called leukotrienes play a role, as they elevate during this process and may be related to the development of menstrual cramps, notes MedicineNet.
According to Healthline, some pain during menstruation is normal, but a doctor should be notified if the menstrual pain interferes with a woman's ability to perform routine tasks each month.