Intrauterine Device (IUD) and Intrauterine System (IUS) are a type of long-acting reversible contraceptive (LARC). This form of contraception involves placing a small flexible plastic or copper device in the uterus to prevent the sperm and egg from meeting and resulting in a pregnancy. IUD/ IUS are 99% effective in preventing a pregnancy. These devices must be placed and removed only by a trained doctor.