IUD
An IUD is a small plastic and copper device that is put into your uterus (womb). It has one or two threads on the end. These thin threads hang through the opening at the entrance of your uterus (cervix) into the top of your vagina.
www.mirena-us.com
http://www.fpa.org.uk/contraception-help/iud-intrauterine-device#DMPRFmDTLLPMJzUZ.99