The intrauterine device is a contraception method. It consists of a T-shaped device, generally in plastic, which is place in the uterus by a GP or gynecologist. There are several different types of intrauterine device, such as non-hormonal devices, and hormonal devices that contain copper. Intrauterine devices all share the same role of preventing the ovum from implanting in the endometrium, the uterine lining, which therefore prevents its initial development into a fetus. The device is implanted during the patient's periods and is effective for 5 years. The uterus can sometimes be measured using what is called a sound, then the intrauterine device is inserted through the cervix via a thin tube called an inserter that is then removed. Not all women, however, are able to use this type of contraception, as there are some contra-indications.