The What, the Why, the Where, the When, and the How-to: An IUD (intrauterine device) -- sometimes also called an IUS or IUC -- is a small device which is inserted into the uterus, through the vagina and cervix by a sexual healthcare provider, and which remains in the uterus until removed. Believe it or not, it's still a bit of a mystery as to how and why IUDs work, but we know for a fact and through a lot of study and use that they DO work, and are incredibly effective. But basically, an IUD give sperm the message that there's no vacancy in the uterus, so there's no sense in them trying to find an egg to shack up with in there: IUDs interfere with sperm mobility and egg fertilization. The copper in the Copper-T IUD is also believed to act as a sort of natural spermicide, and the hormone in the Mirena IUD also thins the lining of the uterus, and thickens cervical mucus, both adding a backup means of protection.


http://www.scarleteen.com/birth_control_bingo_intrauterine_devices_iud


looks like they are ready to give it to teens if they want it.