The IUD is a T-shaped plastic object inserted into the uterus to provide birth control. Mirena, Skyla, Liletta, and Kyleena are IUDs that use the hormone progestin. Paragard does not release progestin, rather, a copper wire coiled around the device produces an inflammatory reaction that is toxic to sperm and eggs (ova). If conception or implantation occurs with a copper IUD, it can cause a miscarriage. All IUDs work to thicken cervical mucus to decrease the chance of sperm entering the uterus to fertilize an egg. If conception occurs with the hormone IUD, progestin thins the lining of the uterus, making it more difficult for an embryo to implant into the uterus.
