The IUS (intrauterine system or Mirena) is similar to the IUD, as it is a small plastic device which is placed in the womb. You do not need to have had a baby first to have an IUS fitted. It is suitable for women of all ages.
It is a plastic T-shaped device which contains the hormone progestogen. The IUS is a long-term contraceptive which can be left in place for between five to seven years depending how old you were when it was fitted.
You do not have to have had a baby first to have an IUS and women of any age can usually use this.
How does it work?
The progestogen released by the IUS works in several ways to prevent a woman from getting pregnant. It:
- thickens cervical mucus to prevent sperm from entering the canal to the womb and being able to reach an egg
- thins the lining of the womb so that if an egg was fertilised it would not be able to implant
- may on occasion stop eggs from being released (ovulation)
- as the IUS is T-shaped, its arms physically prevent any fertilised eggs from implanting in the womb and developing into a foetus
How effective is it?
The IUS is over 99% effective at preventing pregnancy.
Advantages of the IUS:
- it can be fitted at any time if it is certain that you are not already pregnant
- it is available at a range of sites, including CASH, GUM and other sexual health clinics, GPs and abortion services
- you don’t have to remember to take anything
- it does not interrupt sex
Your periods will probably be shorter and lighter, and for some women may stop completely.
Your periods and fertility will return quickly if the IUS is removed
Disadvantages of the IUS:
- to have an IUS fitted, you usually need two appointments, one for your initial chat and check up, and one for your actual fitting of the IUS
- the fitting can be uncomfortable/painful, however local anaesthetic is usually used
- it needs to be fitted by a specially trained doctor or nurse
- if you have a sexually transmitted infection from unprotected sex and have an IUS fitted you could get a pelvic infection.
When you have the IUS fitted you may initially experience side effects, such as:
- breast tenderness
- spotty skin
- irregular periods, which some women find annoying or worrying (however, for most women this settles within the first 6 to 12 months after fitting)
- there is a small chance that you could develop an infection after having the IUS fitted. Very rarely, having the IUS fitted may perforate (make a small hole in) your womb. This is not likely if the doctor or nurse fitting your IUS has lots of experience.
Things to bear in mind:
The IUS does not provide any protection against sexually transmitted infections, including HIV, like a condom does.
Where can I get it from and how much does it cost?
The IUS is available free on the NHS. You can only get it on prescription and cannot buy it at a pharmacy. The IUS can be obtained from your GP, a sexual health clinic, a practice nurse or a young person's clinic.