Copper IUDs: These non-hormonal devices release copper ions, which are toxic to sperm. They can prevent pregnancy for up to 10 years and are highly effective. Hormonal IUDs: These devices release a small amount of progestin, which thickens cervical mucus and thins the uterine lining to prevent sperm from reaching an egg. They can be effective for 3 to 7 years, depending on the brand.
