Displaced IUD contraceptive. Endoscope view of the thread (centre) of an intrauterine contraceptive device (IUD) penetrating through a perforation in the uterus (womb) into the abdomen. An IUD is a T- shaped piece of metal or plastic that is inserted into the uterus, through the cervix, to prevent pregnancy. It is thought to work by inhibiting the implantation of a fertilised egg. In cases where any part of the IUD has penetrated the uterine wall, the IUD is surgically removed.