What are menstrual cramps and why do they happen?

Menstrual cramps (dysmenorrhea) are a fact of life for many women. They occur just before or on the first few days of menstruation. The pain can be severe and normally subsides after two days. 

Troublesome menstrual cramps should be assessed by a physician. They are not usually associated with underlying medical problems. Primary dysmenorrhea (not associated with a medical problem) is thought to result from increased levels of prostaglandins, which in turn may cause contractions of the uterus and result in pain. In about 10% of women, such pain is accompanied by nausea, vomiting and backaches.

Can menstrual pain be caused by medical problems?