[Menstrual status as risk factors of endometriosis: a case-control study].

A case-control study, involving 203 cases of pelvic endometriosis and 406 randomly selected and age-matched community controls, was conducted. The results showed that women characterized by earlier menarche (< or = 12 years) and longer period (> 7 days) were associated with an elevated risk. Longer cycle (> 35 days) seemed to have a protective effect. There are a tendency to increasing risk for endometriosis associated with primary dysmenorrhea and energetic physical activities during menstruation. The results indicate that intensive treatment of primary dysmenorrhea and avoidance of strenuous exercise during menstruation may prevent pelvic endometriosis.