Dysmenorrhea is the medical term for the painful cramps that may occur immediately before or during the menstrual period. There are two types of dysmenorrhea: primary dysmenorrhea and secondary dysmenorrhea.
Primary dysmenorrhea is another name for common menstrual cramps. Cramps usually begin one to two years after a woman starts getting her period. Pain usually is felt in the lower abdomen or back. They can be mild to severe. Common menstrual cramps often start shortly before or at the onset of the period and continue one to three days. They usually become less painful as a woman ages and may stop entirely after the woman has her first baby.
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. 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. Pain results when part of a muscle briefly loses its supply of oxygen.