Primary dysmenorrhea occurs for no apparent cause.
Secondary dysmenorrhea, usually happening later in life, has an underlying cause. The pain begins just before or at the onset of menstruation and is centered in the lower abdomen. It may be cramp-like, and it lasts for the first day or two of the menstrual period. The abdominal pain may be accompanied by backache, nausea, vomiting, headache, frequent urination or bowel movements, and occasionally by dizziness and fainting. The pain is thought to be a result of uterine contractions.