A contraceptive intrauterine device having a support structure configured for transcervical implantation in a uterus, an active element coupled to the support structure, the active element having a core including copper that is at least partially coated with an outer layer including gold or gold alloy. A contraceptive intrauterine device having a support structure configured for transcervical implantation in a uterus, an active element coupled to the support structure, the active element including a copper core that is at least partially plated or coated with an outer layer including gold or gold alloy, wherein the copper core is configured to release copper ions after the device is implanted in a uterus, and wherein the gold or gold alloy outer layer is configured to control the release rate of copper ions release by the core. Methods for preventing conception by implanting said contraceptive intrauterine devices.