Dysmenorrhea, also known as painful periods, or menstrual cramps, is pain during menstruation. Its usual onset occurs around the time that menstruation begins. Symptoms typically last less than three days. The pain is usually in the pelvis or lower abdomen. Other symptoms may include back pain, diarrhea, or nausea. In young women painful periods often occur without an underlying problem. In older women it is more often due to an underlying issues such as uterine fibroids, adenomyosis, or endometriosis. It is more common among those with heavy periods, irregular periods, whose periods started before twelve years of age, or who have a low body weight.