Intrauterine devices  :

The current intrauterine devices (IUD) are small devices, often 'T'-shaped, often containing either copper or levonorgestrel, which are inserted into the uterus. They are one form of long-acting reversible contraception which are the most effective types of reversible birth control. Failure rates with the copper IUD is about 0.8% while the levonorgestrel IUD has a failure rates of 0.2% in the first year of use. Among types of birth control, they along with birth control implants result in the greatest satisfaction among users. As of 2007, IUDs are the most widely used form of reversible contraception, with more than 180 million users worldwide.
While copper IUDs may increase menstrual bleeding and result in more painful cramps hormonal IUDs may reduce menstrual bleeding or stop menstruation altogether. Cramping can be treated with NSAIDs. Other potential complications include expulsion (2–5%) and rarely perforation of the uterus (less than 0.7%).A previous model of the intrauterine device (the Dalkon shield) was associated with an increased risk of pelvic inflammatory disease, however the risk is not affected with current models in those without sexually transmitted infections around the time of insertion.
Evidence supports effectiveness and safety in adolescents and those who have and have not previously had children. IUDs do not affect breastfeeding and can be inserted immediately after delivery.  They may also be used immediately after an abortion. Once removed, even after long term use, fertility returns to normal immediately.

What are IUDs (intrauterine devices)?

The intrauterine device (IUD) is a method of birth control designed for insertion into a woman's uterus so that changes occur in the uterus that make it difficult for fertilization of an egg and implantation of a pregnancy. IUDs also have been referred to as "intrauterine contraception (IUC). IUDs approved for use in the U.S. contain medications that are released over time to facilitate the contraceptive effect . They may also be used immediately after an abortion. Once removed, even after long term use, fertility returns to normal immediately.

The IUD is a small "T"-shaped device with a monofilament tail that is inserted into the uterus by a health care practitioner in the office setting. When inserted into the uterus, the arms of the "T" are folded down, but they then open out to form the top of the "T". The device rests inside the uterus with the base of the T just above the cervix and the arms of the T extending horizontally across the uterus. A short piece of monofilament string attached to the IUD extends through the cervix into the vagina. This string makes it possible to be sure that the IUD is still in the uterus.