While copper IUDs may increase menstrual bleeding and result in more painful cramps,[68] hormonal IUDs may reduce menstrual bleeding or stop menstruation altogether.[2] Cramping can be treated with painkillers like non-steroidal anti-inflammatory drugs.[69] Other potential complications include expulsion (2–5%) and rarely perforation of the uterus (less than 0.7%).[65][69] A previous model of the intrauterine device (the Dalkon shield) was associated with an increased risk of pelvic inflammatory disease, however the risk is not affected with current models in those without sexually transmitted infections around the time of insertion.[70] IUDs appear to decrease the risk of ovarian cancer.[71]