An IUD is a small device shaped like the letter T that is placed by a healthcare professional into the uterus to prevent pregnancy. There are various types of IUDs. Some are progesterone-only IUDs and may be used for patients who have not had any children or who have a smaller uterus. There are slightly larger IUDs for women who have had children and may have a larger uterus. There are even IUDs that have no hormones at all like the ParaGard that lasts for 10 years.