An intrauterine device (IUD) is a small T-shaped plastic and copper device that's inserted into your womb by a specially trained health professional. There are various types and sizes available. Depending on the type, an IUD can last from three to ten years. It used to be called a coil.

An intrauterine system (IUS) is a small, T-shaped plastic device that contains a progestogen hormone. It's inserted into your womb by a specially trained health professional. Once it's in place, it works for five years.


Both mean you don't have to think about contraception every day or each time you have sex.

How does it work?

The IUD works by preventing sperm from surviving in the cervix, womb or fallopian tubes. It may also prevent a fertilised egg from implanting in the womb.

The IUS also releases a progestogen hormone into the womb, which:

  • Thins the womb lining so that it's less likely to accept a fertilised egg,
  • Thickens the mucus from your cervix, so it's more difficult for sperm to move through and reach an egg.
  • Stops ovulation in some women.

How effective is it?

The IUD and IUS are more than 99% effective. This means that less than one in every 100 women who use one of the new IUD or IUS will become pregnant in one year.

Added benefits?

  • The IUD and IUS are effective as soon as they are put in.
  • Both can be removed at any time by a specially trained health professional. You'll quickly return to normal levels of fertility.
  • Once in place you don't have to think about contraception for up to 10 years depending on the type.
  • Both can be used by women who can't use combined contraception (such as the combined pill), e.g. women who suffer from migraines.
  • The IUS can make your periods lighter, shorter or stop altogether, so it may help women who have heavy or painful periods.

What else should I know?

  • Having the device put in can be uncomfortable. You may want to use pain-relieving drugs or a local anaesthetic. Ask the doctor or nurse about this.
  • There is a small chance of infection when it is initially inserted and may not be suitable if you have had previous pelvic infections.
  • There is a risk that your body may spontaneously expel it.
  • Changes to your periods are common in the first three to six months after being fitted with an IUD, but they're likely to normalise. It can make your periods heavier, longer or more painful, and you might get spotting or bleeding between periods. Heavy bleeding can be treated, so talk to your doctor or nurse about this.
  • Some women may experience mood swings, skin problems or breast tenderness after having the IUS fitted.
  • If you do get pregnant, there's an increased risk of having an ectopic pregnancy (when the egg implants outside the womb, for example in the fallopian tube). But because pregnancy is very unlikely, the overall risk of ectopic pregnancy is lower than in women who don't use contraception.
  • The device must be removed by a trained health professional.

By using condoms as well as other contraception, you'll help to protect yourself against sexually transmitted infections (STIs).