Uterine bleeding of unknown etiology was not associated with cigarette smoking (RR = 1.01, 95 percent CI 0.94-1.08), except for a small increase in risk among the heaviest smokers (RR = 1.29, 95 percent CI 1.04-1.65) (table 5). Once again, no dose-response pattern between number of cigarettes smoked per day and the risk of bleeding was apparent. Alcohol was not found to be associated with bleeding.