An intrauterine device
(called an IUD for short) is a small, plastic, T-shaped device with a string attached to the end (the string is attached so that you can check so often to make sure the IUD is still in place). The IUD is placed inside the uterus
to prevent pregnancy
. This placement can be done during an office visit. Once in place, the IUD stays in your uterus until your doctor removes it. IUD prevents sperm from joining with an egg. It does this by making the sperm unable to go into the egg and by changing the lining of the uterus.