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.
OVERVIEW
EFFICACY
99%+
FREQUENCY
EVERY 3–8 YEARS
EFFECT ON FERTILITY
UPON DISCONTINUATION OF USE, FERTILITY SHOULD RETURN TO NORMAL
BLOOD CLOT RISK
NOT KNOWN TO INCREASE RISK
IUS IS A TYPE OF LONG-ACTING CONTRACEPTION
The IUS belongs to a category of contraceptives called LARCs (long-acting reversible contraceptives). The IUS provides contraception for a long period of time - up to 3 or up to 8 years (long acting). It can also be removed at any point if your plans change and you will return to your normal level of fertility once it is removed (reversible).
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 of your cervix, preventing sperm from entering the uterus.
Inhibiting sperm movement so it’s more difficult to reach and fertilize an egg.
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.
WHY IS IT SO EFFECTIVE?
It’s a very effective option because once fitted by a healthcare professional, the IUS doesn’t rely on you having to remember to take it for it to work.
WHAT’S IT MADE OF?
The IUS is made up of three parts:
PREPARING FOR YOUR GP APPOINTMENT
TALKING TO YOUR DOCTOR
Get the information you need for an informed discussion with your doctor.
PP-UN-WHC-GB-0316 July 2025