An IUD is a small, T-shaped contraceptive device made from plastic and copper that fits inside the womb (uterus). It used to be called a coil or a loop.

It is a long-lasting and reversible method of contraception but it is not a barrier method. This means that an IUD cannot stop you getting sexually transmitted infections (STIs).

There are different types and sizes of IUD to suit different women. IUDs need to be fitted by a trained doctor or nurse at your GP surgery, local family planning clinic or sexual health clinic.

They can stay in the womb for five to 10 years depending on the type. If you are 40 or over when you have an IUD fitted, it can be left in until you reach the menopause or until you no longer need contraception.

Most women can have an IUD fitted, including women who have never been pregnant or who are HIV positive. An IUD is usually fitted during your menstrual period. From the moment the IUD is fitted until the time it is taken out, you are protected against pregnancy.

How it works

An IUD stops sperm from reaching the egg. It does this by releasing copper into the body, which changes the make-up of the fluids in the womb and fallopian tubes. These changes prevent sperm from fertilising eggs. IUDs may also stop fertilised eggs from travelling along the fallopian tubes and implanting in the womb.

How effective is an IUD?

An IUD is 98–99% effective at preventing pregnancy. Newer models that contain more copper are the most effective (over 99% effective). This means that less than one in every 100 women who use the IUD will get pregnant in a year.

As a long-lasting method of contraception, the IUD is very effective. You do not need to remember to take or use contraception to prevent pregnancy. However, it does not protect you against STIs.

Emergency contraception

The IUD can also be used as a method of emergency contraception up to five days after unprotected sex or up to five days after the earliest time you could have released an egg (ovulation). If you have unprotected sex, make an appointment with your GP or clinic as soon as possible.