IUS (Intra Uterine System)

IUS (Intra Uterine System)

The IUS is sometimes called Mirena

How do they work?

  • By making the lining of the womb thinner, so it’s less likely to accept a fertilised egg.
  • By thickening the mucus in the cervix, making it more difficult for sperm to reach an egg.

How long do they last?

  • It works for five years.

How effective is it?

  • The IUS is more than 99 per cent effective as long as it’s in place.
  • The IUS has two soft threads at one end, which hang through the cervix into the top of the vagina. These are so you can check the IUS is in position. If you want to reassure yourself that it’s still in place you may want to gently feel for the threads.
  • As long as it’s in place, on average fewer than one woman in 100 will get pregnant in a year.

How is it fitted?

  • A trained doctor or nurse will fit the IUS by inserting it into your womb via an internal examination. It usually takes about 20 minutes. It can be uncomfortable at the time but you can have a local anaesthetic or painkillers to help with this. You may have some discomfort and light bleeding for a few days afterwards. The person who fits your IUS will advise you.

How is it removed?

  • A trained doctor or nurse will remove the IUS by pulling gently on the small threads attached to it so that it comes out through the cervix and out of your body.


  • Your periods usually become much lighter, shorter and less painful, and they may stop completely after the first year of use, so the IUS is helpful if you have heavy, painful periods.
  • Your normal fertility returns as soon as the IUS is removed.
  • It's easy to remove
  • It's not affected by other medicine

Possible drawbacks

  • You may experience some irregular bleeding or ‘spotting’ at first, but this should settle
  • Some women report having headaches, acne, mood changes and breast tenderness in the first few months following insertion. This usually settles as you get used to the small amount of hormone in the IUS.
  • Insertion must be done carefully by an experienced doctor or nurse as there can be some very rare complications - the clinic will discuss these when you attend.


Image of the female reproductive system with an IUS in place

The IUS is a small T-shaped plastic device that is placed in the uterus and slowly releases the hormone progestogen


Listen to an experience of having an IUS:

> Contraception: Which LARC?

LARCs prevent pregnancy.
Condom use is essential to prevent Sexually Transmitted Infections (STIs).



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