what causes bad period cramps

Bad period cramps are primarily caused by high levels of prostaglandins, hormone-like substances that trigger the uterus to contract strongly to shed its lining during menstruation. These strong contractions cause the cramping and pain felt during periods. Conditions such as endometriosis (where uterine- like tissue grows outside the uterus), adenomyosis (where uterine lining grows into the uterine muscle), fibroids, pelvic inflammatory disease, and uterine defects can also cause more severe or prolonged cramps. Use of intrauterine devices (IUDs) may sometimes cause or worsen cramps as well. Inflammation plays a key role in painful periods, and higher prostaglandin levels correlate with more severe pain.