A small “T-shaped” firm yet flexible plastic is inserted inside the uterus. Two kinds of IUDs are available and they are copper IUDs and hormonal IUDs. Exactly how IUDs prevent pregnancy is not clear, it seems to affect the atmosphere of the uterus making the egg unable to fertilize. Hormonal IUDs work by releasing small amounts of progestin which makes the sperms inactive and prevent fertilization. This form of contraception is very effective, economical and is also reversible. IUDs can be used as a long-term method of contraception which can last between five to ten years. Expulsion of IUDs from the uterus is possible during menstruation. The wearer should ensure its proper placement by checking within the vagina (near cervix) two plastic strings which are attached to the IUD.