Both the copper and hormonal IUDs are more than 99% effective in preventing pregnancy. Copper IUDs are effective immediately after insertion and last for 12 years (depending on the brand). Hormonal IUDs can also be effective immediately depending on where you are in your cycle; otherwise, they reach full effectiveness after one week post-insertion. Depending on the brand of hormonal IUD used, they typically provide pregnancy prevention for up to three to seven years. During your annual exam, make sure your gynecologist checks your IUD to ensure it's still in the right spot and raise any concerns or questions you have regarding your IUD.