Most Recent Answer
by Cleveland Clinic
Menstrual cramps are caused by contractions in the uterus (which is a muscle). The uterus, the hollow, pear-shaped organ where a baby grows, contracts throughout a woman's menstrual cycle. During menstruation, the uterus contracts more strongly. If the uterus contracts too strongly, it can press against nearby blood vessels, cutting off the supply of oxygen to the muscle tissue of the uterus. Pai...