intrauterine device

intrauterine device (IUD), small, T-shaped device inserted into the uterus to provide long-acting, reversible contraception (LARC). Intrauterine devices (IUDs) are reliable and remove risks of user error, such as forgetting to take a daily pill. They are one of the most effective forms of birth control available, preventing pregnancy in 99 percent of instances.

There are two main types of IUDs, hormonal and copper, both of which prevent fertilization of the egg. Hormonal IUDs do so by continuously releasing a synthetic hormone (progestin) that thickens cervical mucus to prevent sperm from reaching the egg and thins the uterine lining; some hormonal IUDs suppress ovulation. Copper IUDs work through the release of copper ions, which impair the viability of sperm. Protection begins immediately after insertion for copper IUDs and within about a week for most hormonal IUDs; some hormonal IUDs inserted within seven days of menstruation may provide immediate protection. Depending on the specific product, a hormonal IUD can provide protection for three to eight years, while some copper IUDs can last as long as 10 years. They can be removed at any time, after which fertility usually returns quickly.

IUDs are associated with various side effects. For example, hormonal IUDs typically result in lighter, less painful periods, or even no period at all, and for this reason they are sometimes used to help manage such conditions as heavy and painful periods, endometriosis, polycystic ovarian syndrome (PCOS), and symptoms related to perimenopause. Copper IUDs may cause heavier and longer periods with more cramping, especially in the first few months after insertion. Some individuals experience hypersensitivity reactions to progestins released by hormonal IUDs or copper ions released by copper IUDs, and in some cases, other inflammatory and immune responses occur, which may be severe enough to prompt device removal. For both types of IUDs there is a risk of expulsion, in which the IUD slips out, as well as a risk of infection shortly after insertion. In rare cases uterine perforation, in which a tear forms in the wall of the uterus, occurs.