An IUS is a small T-shaped plastic device that is put into your uterus (womb). It releases a progestogen hormone. This is similar to the natural progesterone that women produce in their ovaries.
The IUS has two threads at one end which hang through the opening at the entrance of your uterus into the top of your vagina.
It works for up to five years. If you are aged 45 or older when the IUS is fitted, it can be left in until the menopause.