Suppression of ovulation, which would otherwise cause damage to the ovarian epithelium and, consequently, inflammation, is generally protective. This effect can be achieved by having children, taking combined oral contraceptives, and breast feeding, all of which are protective factors. A longer period of breastfeeding correlates with a larger decrease in the risk of ovarian cancer. Each birth decreases risk of ovarian cancer more, and this effect is seen with up to five births. Combined oral contraceptives reduce the risk of ovarian cancer by up to 50%, and the protective effect of combined oral contraceptives can last 25–30 years after they are discontinued. Regular use of aspirin or acetaminophen (paracetamol) may be associated with a lower risk of ovarian cancer; other NSAIDs do not seem to have a similar protective effect.