An intrauterine device is a contraception method. It consists of a T-shaped device, generally made of plastic, which is placed in the uterus by a GP or gynecologist. There are several different types of intrauterine device, such as non hormonal devices, and hormonal devices containing 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. As it does not specifically prevent fertilization, it is more correctly defined as an abortifacient. Devices containing copper have an added toxic effect on spermatozoa. The device is implanted during the patient's periods and is effective for 5 years. Not all women, however, are able to use this type of contraception, as there are some contra-indications.