Contraception: Intrauterine Devices (IUDs)

An Intrauterine Device (IUD) is a small device (usually T-shaped) made from plastic and copper that is designed for insertion into the uterus (womb). IUDs can remain in place for between five and 10 years depending on the type used. They are 98 to 99 per cent effective as contraceptive devices and once inserted need no further maintenance beyond checking that they are still in place. They used to be known as "coils".

How do they work?

Although the mechanism is not fully understood it is thought that IUDs work in a number of ways to interfere with the possible implantation of an egg. They stop sperm from reaching the egg and alter the chemical balance of the environment within the womb so that an egg will not implant.

What are the advantages of an IUD?

  • IUDs continue to be effective for five to 10 years (depending on the device used) and can be removed at any time.
  • An IUD is a good method of contraception for women who are spacing their pregnancies and are over 25.

What are the disadvantages of IUDs?

  • An IUD has to be fitted into position. This may be a little uncomfortable and a painkiller may be given prior to insertion.
  • At first periods may be heavier, longer or more painful than before insertion of the device. IUDs are, therefore, not suitable for women who already have painful, heavy periods.
  • IUDs provide no protection against sexually transmitted diseases, including HIV.

Are any regular checks necessary?

Each IUD has two threads attached to it, which come through the cervix into the womb. The doctor or nurse will show you how to feel the threads - they need to be checked regularly each month to ensure that the device is still in the correct position.

The IUD will usually be checked by a doctor or nurse within six to eight weeks of insertion and then once a year unless there is a problem.

What types of IUD are available?

There are several different types and sizes of IUDs available. The doctor fitting the device will decide on the most suitable type for you.

Further information available from:

FPA (Sexual Health Charity)
23-28 Penn Street
London N1 5DL
Tel: 020 7608 5240

Fact sheet provided by MIMS

Date last reviewed: September 2016

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