Final answer:
An intrauterine device (IUD) is a T-shaped or coiled plastic structure that is inserted into the uterus and is highly effective in preventing pregnancy.
Step-by-step explanation:
An intrauterine device (IUD) is a T-shaped or coiled plastic structure that is inserted into the uterus via the vagina and cervix that contains either copper or a hormone. It is inserted by a physician and may be left in place for months or even years.
The copper in copper IUDs prevents pregnancy by interfering with the movement of sperm so they cannot reach and fertilize an egg. Almost no one gets pregnant who uses this method.