Intra Uterine System (IUS)

What is it?

An Intra-Uterine System (IUS) is small, T-shaped plastic device that is inserted into the uterus (womb). The IUS that is available in the UK is called Mirena.

An IUS releases the hormone progestogen and works by:

  • Thickening cervical mucus to prevent sperm reaching an egg
  • Thinning the lining of the uterus to stop eggs from implanting
  • Stops a fertilised egg from implanting in the uterus
  • A nurse or doctor will fit the IUS. There is a brief internal examination, followed by the fitting which takes 15-20 minutes. Once an IUS is fitted, it will need to be checked by a doctor or at your sexual health clinic after 3 to 6 weeks

How effective is it?

An IUS is more than 99% effective at preventing pregnancy. This means that less than 1 out of 100 women who use the IUS will become pregnant in a year.

What are the advantages?

  • Once the IUS is in place, you don't have to think about contraception for five years
  • An IUS is useful if you forget to take a pill at the same time every day
  • Once an IUS is removed your fertility (ability to have children) quickly returns to normal
  • It is not affected by other medicines
  • It is safe to breastfeed after an IUS is fitted
  • It can make your periods lighter, shorter or stop altogether, so it may help women who have heavy or painful periods
  • What else do I need to know?
  • It does not protect you against STIs so always use a condom
  • May not be suitable for some women - a full medical history should be taken

Where can I get an IUS?

Find your nearest services using our services page.


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 Lambeth Teenage Pregnancy and Parenthood Partnership
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