It normally occurs at the approximate monthly intervals of menstruation. Two main types are recognized. Primary dysmenorrhea is a natural process that is a normal part of menstruation.
Secondary dysmenorrhea has an additional underlying cause due to disease or other malfunction.
Cause The exact cause of menstrual pain remains unknown. The primary type is thought to result mainly from contractions of the uterus similar to but weaker than those that occur during childbirth. Such contractions are triggered by a hormonelike chemical, prostaglandin, that is produced with menstruation. Secondary dysmenorrhea appears during the menstrual cycle but is caused in most cases by infection, inflammation , or other disorder of the woman's reproductive organs. Only women develop the menstrual pain of primary dysmenorrhea .