Copper-T is an intrauterine device (IUD) used by women as a birth control. An IUD is a small device which is placed inside the uterus. The vertical and horizontal arms of the Copper - T contain copper which is slowly released into the uterine cavity. Copper stops sperm from making their way up through the uterus into the tubes, and it reduces the ability of sperm to fertilize the egg. It also prevents a fertilized egg (blastocyst) from successfully implanting in the lining of the uterus if fertilization has occurred.