Health Library
The intrauterine device (IUD) is a birth control method inserted into the uterus that provides long-term contraception. There are two main types: copper IUDs and hormonal IUDs. The copper IUD prevents fertilization by disrupting sperm movement, while the hormonal IUD (containing levonorgestrel) prevents pregnancy by thickening cervical mucus and thinning the endometrium. IUDs are considered long-acting reversible contraceptives (LARCs) and have very high effectiveness rates.