IUD IUD stands for intrauterine device, a T-shaped piece of plastic that is placed inside the uterus by a doctor. The copper IUD, ParaGard, works for as long as 12 years. The hormonal IUD, Mirena, must be replaced after 5 years. Both types make it more difficult for sperm to fertilize the egg. Fewer than eight in 1,000 women get pregnant. Pros: Long-lasting, low-maintenance. Cons: Irregular or heavier periods. More expensive upfront, may slip out, may cause side effects.