Intrauterine System (IUS)
An IUS is a small, T-shaped plastic device that's put into your womb (uterus) by a doctor or nurse.
It releases the hormone progestogen to stop you getting pregnant and lasts for 3 to 5 years.
Two brands of IUS are used in the UK: Mirena and Jaydess.
At a glance: facts about the IUS
- When inserted correctly, it's more than 99% effective.
- It can be taken out at any time by a specially trained doctor or nurse. It's possible to get pregnant straight after it's removed.
- It can make your periods lighter, shorter or stop altogether, so it may help women who have heavy or painful periods.
- It can be used by women who can't use combined contraception (such as the combined pill) – for example, those who have migraines.
- Once the IUS is in place, you don't have to think about it.
- Some women may experience side effects, such as mood swings, skin problems or breast tenderness.
- There's a small risk of getting an infection after it's been fitted.
- It can be uncomfortable when the IUS is put in, but painkillers can help.
- The IUS can be fitted at any time during your monthly menstrual cycle, as long as you're not pregnant.
- The IUS doesn't protect against sexually transmitted infections (STIs), so you may need to use condoms as well.
How it works
The IUS is similar to the intrauterine device (IUD), but instead of releasing copper like the IUD, it releases the hormone progestogen into the womb.
It thickens the cervical mucus, which makes it more difficult for sperm to move through the cervix, and thins the lining of the womb so an egg is less likely to be able to implant itself.
For some women, it can also prevent the release of an egg each month (ovulation), but most women continue to ovulate.
If you're 45 or older when you have the IUS fitted, it can be left in until you reach the menopause or no longer need contraception.
Having an IUS fitted
An IUS can be fitted any time in your menstrual cycle, as long as you're not pregnant.
If it's fitted in the first 7 days of your cycle, you'll be protected against pregnancy straight away.
If it's fitted at any other time, use additional contraception, such as condoms, for 7 days afterwards.
Before your IUS is fitted, a GP or nurse will check inside your vagina to check the position and size of your womb.
You may be tested for any existing infections, such as STIs, and be given antibiotics.
The appointment takes about 15 to 20 minutes, and fitting the IUS should take no long than 5 minutes:
- the vagina is held open, like it is during a smear test (cervical screening)
- the IUS is inserted through the cervix and into the womb
Having an IUS fitted can be uncomfortable, but you can have a local anaesthetic to help. Discuss this with a GP or nurse beforehand.
You may also get period-type cramps afterwards, but painkillers can ease the cramps.
Once an IUS is fitted, it'll need to be checked by a GP after 3 to 6 weeks to make sure everything is fine.
Tell the GP if you have any problems after this initial check or you want to have it removed.
See a GP if you or your partner are at risk of getting an STI, as this can lead to infection in the pelvis.
You may have an infection if you have:
- pain in your lower abdomen
- a high temperature
- smelly discharge
How to tell if it's still in place
An IUS has 2 thin threads that hang down a little way from your womb into the top of your vagina.
The GP or nurse that fits your IUS will teach you how to feel for these threads and check that the IUS is still in place.
Check your IUS is in place a few times in the first month and then after each period, at regular intervals.
It's very unlikely that your IUS will come out, but if you can't feel the threads or think it's moved, you may not be protected against pregnancy.
See a GP or nurse straight away and use additional contraception, such as condoms, until your IUS has been checked.
If you've had sex recently, you may need emergency contraception.
Your partner shouldn't be able to feel your IUS during sex. If they can, see a GP or nurse for a check-up.
Removing an IUS
Your IUS can be removed at any time by a trained doctor or nurse.
If you're not having another IUS put in and don't want to become pregnant, use additional contraception, such as condoms, for 7 days before you have it removed.
It's possible to get pregnant as soon as the IUS has been taken out.
Who can use an IUS?
Most women can use an IUS, including those who are HIV positive. A GP or nurse will ask about your medical history to check if an IUS is suitable contraception for you.
The IUS may not be suitable if you have:
- breast cancer, or have had it in the past 5 years
- cervical cancer or womb (uterus) cancer
- liver disease
- unexplained bleeding between periods or after sex
- arterial disease or a history of serious heart disease or stroke
- an untreated sexually transmitted infection (STI) or pelvic infection
- problems with your womb or cervix
Using an IUS after giving birth
An IUS can usually be fitted 4 to 6 weeks after giving birth (vaginal or caesarean). You'll need to use alternative contraception from 3 weeks (21 days) after the birth until the IUS is put in.
In some cases, an IUS can be fitted within 48 hours of giving birth. It's safe to use an IUS when you're breastfeeding, and it won't affect your milk supply.
Using an IUS after a miscarriage or abortion
An IUS can be fitted by an experienced GP or nurse straight after an abortion or miscarriage. You'll be protected against pregnancy immediately.
Advantages and disadvantages of the IUS
- It works for 5 years (Mirena) or 3 years (Jaydess).
- It's one of the most effective forms of contraception available in the UK.
- It doesn't interrupt sex.
- Your periods can become lighter, shorter and less painful – they may stop completely after the first year of use.
- It's safe to use an IUS if you're breastfeeding.
- It's not affected by other medicines.
- It may be a good option if you can't take the hormone oestrogen, which is used in the combined contraceptive pill.
- It's possible to get pregnant as soon as the IUS is removed.
- There's no evidence that an IUS will affect your weight or increase the risk of cervical cancer, cancer of the uterus or ovarian cancer.
- Your periods may become irregular or stop completely, which may not be suitable for some women.
- Some women experience headaches, acne and breast tenderness after having the IUS fitted.
- Some women experience changes in mood and libido, but these changes are very small.
- An uncommon side effect of the IUS is that some women can develop small fluid-filled cysts on the ovaries – these usually disappear without treatment.
- An IUS doesn't protect you against STIs, so you may need to use condoms as well.
- If you get an infection when you have an IUS fitted, it could lead to a pelvic infection if it's not treated.
- Most women who stop using an IUS do so because of vaginal bleeding and pain, although this is less common.
Risks of the IUS
There's a very small chance of getting a pelvic infection in the first 20 days after the IUS has been inserted.
You may be advised to have a check for any existing infections before an IUS is fitted.
It's not common, but the IUS can be rejected (expelled) by the womb or it can move (displacement).
If this happens, it's usually soon after it's been fitted. You'll be taught how to check that your IUS is in place.
Damage to the womb
In rare cases, an IUS can make a hole in the womb when it's put in. This may be painful, but often there are no symptoms.
If the GP or nurse fitting your IUS is experienced, the risk is extremely low. See a GP straight away if you're feeling pain, as you may need surgery to remove the IUS.
If the IUS fails and you become pregnant, there's also a small increased risk of ectopic pregnancy.
Where to get the IUS
You can get the IUS for free, even if you're under 16, from:
- contraception clinics
- sexual health or genitourinary medicine (GUM) clinics
- GP surgeries
- some young people's services
If you're under 16 years old
Contraception services are free and confidential, including for people under the age of 16.
If you're under 16 and want contraception, the doctor, nurse or pharmacist won't tell your parents or carer as long as they believe you fully understand the information you're given and the decisions you're making.
Doctors and nurses work under strict guidelines when dealing with people under 16. They'll encourage you to consider telling your parents, but they won't make you.
The only time a professional might want to tell someone else is if they believe you're at risk of harm, such as abuse. The risk would need to be serious, and they would usually discuss this with you first.