About the intrauterine system (IUS)
An IUS is a small flexible plastic device that is inserted into your womb by a specially trained doctor or nurse. It looks like a letter T and when inserted releases a progestogen hormone. An IUS last from three to five years and is estimated to be over 99% effective. It has a very low failure rate of just 1 in 2000 cases making it one of the most effective forms of contraception available in the UK.
There are two different types of IUS. Both work in the same way but last for different periods of time as they release different amounts of the hormone. For more information on the different types, check the Useful Links at the end of this page.
How it works
The IUS releases a progestogen hormone, similar to those naturally released by the ovaries. This:
- Thickens the mucus at the entrance to the womb, making it difficult for sperm to pass and reach an egg
- Thins the lining of the womb to prevent an egg that has joined with a sperm from growing in the womb
- In some women, it also stops the release of an eggs some of the time
How to use it
A doctor or nurse will fit your IUS. This usually takes 10 to 20 minutes. The IUS will be inserted into your vagina and then into your womb. They will explain how to feel for the two threads that hang down so you can check that it is still in place.
If you feel unwell, have pain in your lower stomach with a high temperature or smelly discharge from your vagina, go back to the clinic where it was fitted. You may have an infection.
Who can use it
Most women can use an IUS. This includes young women, women who have never been pregnant, and those who are HIV positive. You may not be able to use an IUS if you have:
- Breast cancer (or have had it in the last five years)
- Cervical cancer
- Liver disease
- Arterial disease or history of serious heart disease or stroke
- An untreated STI or pelvic infection
- Rare problems with your womb (present since or before birth)
There are many advantages to using the IUS:
- Lasts from three to five years
- One of the most effective forms of contraception available in the UK
- Periods may become much lighter, shorter, usually less painful and may even stop completely after the first year of use
- Safe to use while breastfeeding
- Not affected by other medicines
- Good for women who can’t take the hormone oestrogen
- Fertility returns to normal when the IUS is removed
It’s also worth bearing in mind that with the IUS:
- The procedure can cause some discomfort but painkillers can help
- In very rare cases, some women experience acne, mood swings, headaches and breast tenderness
- Some women may experience irregular vaginal bleeding and spotting in the first six months
- It doesn’t protect against STIs. You may have to use condoms as well
There is also a small increased risk of:
- Infection after IUS is first fitted if an infection is present at the time of fitting
- The IUS making a hole in the womb or neck of the womb. This is a very low risk if fitted by an experienced clinician (1 in 1000 cases)
- The IUS coming out. There is a very small risk of this and your doctor or nurse will teach you how to check it is in place
- Developing small cysts filled with fluid on the ovaries – these usually disappear without treatment
- In the very rare event of a pregnancy, there is an increased risk of an ectopic pregnancy.
Where to get it
Most types of contraception are free in the UK. Contraception is free to all women and men through the NHS. You can get an IUS fitted in contraception or sexual health clinics and some GP surgeries. Not all doctors or nurses will fit an IUS so make sure you mention you would like to discuss an IUS when making the appointment.
An IUS is best fitted at the beginning of your monthly cycle when you are on your period. This will rule out pregnancy.