An Intrauterine device (intra meaning within, and uterine meaning of the uterus), is a birth control device also known as an IUD or a coil. It is a flexible T-shaped plastic device placed in the uterus and is the world's most widely used and inexpensive method of reversible birth control.
The device has to be fitted inside the uterus (and removed) by a doctor or qualified medical practitioner. As such it is inside the woman all of the time.
One type of device continuously releases small amounts of progestin and has to be exchanged every year. Another type contains copper and can remain in place for 10 years. The device affects the lining of the uterus (the endometrium), but the exact mechanism is not known.
The device is more reliable than birth control pills but less reliable than Norplant. As it is not a barrier method, cannot prevent the transfer of sexually transmitted diseases.
The device may be uncomfortable to wear, and can make the woman more vulnerable to infections of the uterus.
A study of women found that those using an IUD had up to twice the normal levels of copper in their blood-stream. This had leached directly from the device into their circulatory systems. Although not at levels known to be acutely poisonous, and thus immediately damaging to health, the effects of long-term exposure to elevated levels of copper are unknown.
Some early IUDs, notably the "Copper-7" injured many of the women fitted with them, with a large number rendered permanently infertile.