First the Facts

  • An intrauterine system (IUS) is a small, plastic, T-shaped device that sits inside the womb
  • Also known as the ‘hormonal coil’
  • Over 99% effective
  • Prevents pregnancy by releasing a hormone
  • Lasts 3–5 years depending on the brand
  • Fitted and removed by a specialist doctor or nurse
  • Does not protect against sexually transmitted infections (STIs)

How Does It Work?

  • An IUS contains a hormone called progestogen
  • Progestogen thins the lining of the womb so that a pregnancy cannot develop
  • It also thickens the mucus in the cervix (neck of the womb), preventing sperm from entering the womb
  • There are several types of IUS available
  • In the UK we use Mirena®, Levosert®, Jaydess® and Kyleena®
  • Over 99% effective: less than 1 person per 100 users will fall pregnant within a year

Does It Work Straight Away?

An IUS does not always work straight away, it depends when it is fitted:

  • If an IUS is fitted within the first 7 days of your period, it will work straight away
  • If an IUS is fitted after day 7 of your period, you must use another contraceptive (e.g. condoms) for 7 days. This is because it will take 7 days for the IUS to start working
  • An IUS can be fitted 4 weeks after childbirth or within the first 48 hours of delivery. You cannot get pregnant within 21 days of childbirth, but you must use additional contraception after this time. If an IUS is fitted more than 21 days after childbirth, you should use condoms for 7 days
  • It works straight away if fitted within 5 days of complete miscarriage or abortion. If it is fitted after this, you must use condoms for 7 days

Are There Any Side Effects?

  • Irregular bleeding can occur, especially in the first few months. This is a process and not a genuine side effect. It represents the lining of the womb thinning and usually settles with time
  • Periods often get lighter and may stop altogether. This is safe and nothing to worry about
  • Acne, breast tenderness and mood changes can sometimes occur
  • Future fertility is not affected by an IUS; you can become pregnant as soon as it is removed
  • There is a small risk of infection and/or damage to the womb when it is fitted
  • Rarely, an IUS can get stuck in the womb or fall out
  • Although the IUS is very effective, if a pregnancy did occur, there is increased risk this would be an ectopic pregnancy. This is when a pregnancy develops outside the womb, such as in the fallopian tube

How Is It Fitted?

  • A specialist nurse or doctor will fit the IUS for you
  • You will be examined to assess the size and position of your womb
  • A speculum is used to open the vagina and visualise the cervix (neck of the womb)
  • The IUS is gently inserted through the cervix and into the womb
  • A local anaesthetic can be used to reduce any pain
  • The procedure is very quick and will only take a few minutes
  • You may experience some cramping and bleeding afterwards, but this will settle down in a few days
  • Rarely, the IUS can damage the wall of the womb. This is called perforation

How Do I Know It Is in the Correct Place?

  • The IUS contains two soft threads attached to the bottom of the device
  • These threads pass through the cervix and sit at the top of the vagina
  • Your partner will not be able to feel the threads during sexual intercourse
  • You can check the IUS is still in place by inserting a finger into the top of the vagina and feeling for the threads
  • It is important to regularly check your threads so that you know the IUS is still in place
  • If you can no longer feel the threads, speak to your doctor and use another method of contraception until it can be identified. This is because the IUS might have fallen out

When Is It Removed?

  • The IUS provides contraception for 3–5 years depending on the type you have:
    • Mirena®, Levosert® and Kyleena® can remain in place for 5 years
    • Jaydess® can remain in place for 3 years
  • You will be provided with written information advising you when your IUS needs to be changed
  • A specialist nurse or doctor can remove the IUS for you at any time
  • A speculum is used to find the threads of the IUS. It is removed by gently pulling on the threads

Where Can I Get an IUS Fitted/Removed?

You can get an IUS fitted free of charge at:

  • A sexual health, genitourinary medicine or contraception clinic
  • Some young person’s clinics
  • Some GP surgeries

Is It Right for Me?

An IUS is safe to use in the majority of users; however, there are some circumstances where it may not be appropriate.

Always discuss with the doctor or nurse if:

  • There is a chance you are already pregnant
  • You have symptoms of infection or have been recently diagnosed with an STI such as chlamydia or gonorrhoea
  • Your womb is an abnormal shape
  • You have a history of breast, cervical or womb cancer or severe liver disease
  • You have bleeding in between your periods or after sex which has not been investigated


Written by: Dr David Rook and Dr Paula Briggs
Last updated: January 2021

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