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Intrauterine system (IUS)

INTRAUTERINE

SYSTEM (IUS)

Other names: the hormonal IUD; the hormonal coil

WHAT IS THE IUS?

A small plastic, T-shaped device which sits inside the uterus (womb) and releases a small amount of hormone to stop you getting pregnant.

It is one of the most effective types of contraception and will keep you protected from pregnancy for up to 3 to 8 years, depending on the IUS you choose.

T-shaped device

OVERVIEW

EFFICACY

EFFICACY

99%+

FREQUENCY

FREQUENCY

EVERY 3–8 YEARS

EFFECT ON FERTILITY

EFFECT ON FERTILITY

UPON DISCONTINUATION OF USE, FERTILITY SHOULD RETURN TO NORMAL

BLOOD CLOT RISK

BLOOD CLOT RISK

NOT KNOWN TO INCREASE RISK

HOW DOES THE IUS WORK?

The IUS works locally in your uterus (womb). It slowly releases a small amount of hormone, a progestogen called levonorgestrel into your uterus.

This prevents pregnancy by:

Thickening-the-mucus

Thickening the mucus of your cervix, preventing sperm from entering the uterus.

Inhibiting sperm

Inhibiting sperm movement so it’s more difficult to reach and fertilize an egg.

Thickening-the-mucus

Thinning the lining of your uterus, making it less likely for an egg to attach to the uterus. This also causes lighter periods or no periods for some women.

HOW EFFECTIVE IS THE IUS AT PREVENTING PREGNANCY?

The IUS is over 99% effective at preventing pregnancy with both perfect use and typical use, meaning that less than 1 in 100 women will get pregnant every year if they have an IUS.

PERFECT USE*

99
%
+

Effective

Approximately

1 out of every 100 women
in a year will experience an unintended pregnancy.

 

* Perfect use of a contraceptive method is when it is used correctly all the time.

TYPICAL USE*

99
%
+

Effective

Approximately

1 out of every 100 women
in a year will experience an unintended pregnancy.

 

* Typical use is what generally happens in real life. It takes into account human error e.g. forgetting to take your pill. The typical and perfect use for the IUS are the same.

Without contraception 85 in 100 women will get pregnant in a year.

WHAT’S IT MADE OF?

The IUS is made up of three parts:

ius

    Made of soft plastic. The arms are flexible and fold down inside the insertion tube whilst the IUS is being fitted. The arms unfold when it is in the uterus.

    Contains the hormone Levonorgestrel and is covered in a release rate controlling silicone membrane. This membrane allows the slow, continuous release of a very small amount of hormone into the uterus.

    Two soft threads attached to the end of the t-frame. These threads hang through the cervix into the top of the vagina. This make it possible to remove it easily, if needed. Usually, your partner won't be able to feel the threads during sex but if they can it shouldn’t cause any pain.

    DOES THE IUS CONTAIN HORMONE?expand_less

    Yes. It contains a progestogen hormone (called Levonorgestrel) which is similar to the hormone progesterone made naturally in your body by your ovaries.

    The IUS does not contain oestrogen.

    The IUS is not suitable for everyone. To find out whether the IUS is right for you, talk to a GP, nurse or pharmacist.

    The IUS may not be suitable if you:

    • Know or suspect you might be pregnant.
    • Have or have had certain types of cancer.
    • Have liver disease.
    • Have unexplained bleeding between periods or after sex.
    • Have arterial disease or a history of serious heart disease or stroke.
    • Have current or recurrent pelvic inflammatory disease.
    • Have an untreated sexually transmitted infection (STI) or genital infection.
    • Have problems with your womb or cervix e.g. fibroids.
    • Have or have had an abnormal smear test (changes in the cervix).
    • Had an inflamed or infected womb after delivery or abortion, during the past 3 months.
    • Have a condition associated with increased susceptibility to infections.

PP-UN-WHC-GB-0316 July 2025