IUS (intrauterine system)

An IUS is a small, T-shaped plastic device that is inserted into your womb (uterus) by a specially trained doctor or nurse.

The IUS releases a progestogen hormone into the womb. This thickens the mucus from your cervix, making it difficult for sperm to move through and reach an egg. It also thins the womb lining so that it's less likely to accept a fertilised egg. It may also stop ovulation (the release of an egg) in some women.

The IUS is a long-acting reversible contraceptive (LARC) method. It works for between 3 and 6 years, depending on the type, so you don't have to think about contraception every day or each time you have sex. Three brands of IUS are used in the UK – Mirena, Levosert and Jaydess. There are several brands of IUS available. For example, Benilexa, Levosert, Jaydess, Kyleena and Mirena. Mirena, Levosert and Benilexa have the same amount of horomone (52mcg) in them. Kyleena has less and Jaydess has the least.

You can use an IUS whether or not you've had children.

At a glance: facts about the IUS

It's more than 99% effective. Less than 1 in every 100 women who use a 52mcg IUS will get pregnant in 5 years, and less than one in 100 who use Jaydess will get pregnant in 3 years.

It can be taken out at any time by a specially trained doctor or nurse and your fertility quickly returns to normal.

The IUS can make your periods lighter, shorter or stop altogether, so it may help women who have heavy periods or painful periods. Jaydess is less likely than a 52mcg IUS to make your periods stop altogether.

It can be used by women who can't use combined contraception (such as the combined pill) – for example, those who have migraines.

Some women may experience mood swings, skin problems or breast tenderness. These usually settle in a few weeks.

There's a small chance of getting an infection in the womb after it's inserted. This shows up within 3 weeks after it goes in.

It can be uncomfortable when the IUS is put in, although painkillers can help with this.

The IUS can be fitted at any time during your monthly menstrual cycle, as long as you're definitely not pregnant. Ideally, it should be fitted within 7 days of the start of your period, because this will protect against pregnancy straight away. You should use condoms for 7 days if the IUS is fitted at any other time.

The IUS does not protect against sexually transmitted infections (STIs). Use condoms as well as the IUS, to protect yourself against STIs.

How an IUS works

The IUS works in a different way to the IUD (intrauterine device). Rather than releasing copper like the IUD, the IUS releases a progestogen hormone. This is like the natural hormone progesterone that's produced in a woman's ovaries.

Progestogen thickens the mucus from the cervix (opening of the womb), making it harder for sperm to move through it and reach an egg. It also causes the womb lining to become thinner and less likely to accept a fertilised egg. In some women, the IUS also stops the ovaries from releasing an egg (ovulation), but most women will continue to ovulate.

If you're 45 or older when you have the IUS fitted, it can be left until you reach menopause or you no longer need contraception.

Having an IUS fitted

An IUS can be fitted at any stage of 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, you need to use another method of contraception (such as condoms) for 7 days after it's fitted.

Before you have an IUS fitted, you'll have an internal examination to determine the size and position of your womb. This is to make sure that the IUS can be positioned in the correct place.

You may also be tested for any existing infections, such as STIs. It's best to do this before an IUS is fitted so that any infections can be treated. You may be given antibiotics at the same time as an IUS is fitted.

It takes about 10 to 20 minutes to insert an IUS.

The fitting process can be uncomfortable or painful for some women, and you may also experience cramps afterwards.

You can ask for a local anaesthetic or painkillers before having the IUS fitted. Discuss this with your GP or nurse beforehand. An anaesthetic injection itself can be painful, so many women have the procedure without one.

It's important that the IUS threads are checked about 6 weeks after it is put in. Most people do this themselves, but you can ask a doctor or nurse to check it for you if you don't want to do it.

Also speak to your GP if you or your partner are at risk of getting an STI, as this can lead to infection in the pelvis.

See your GP or go back to the clinic if you have:

• pain in your lower abdomen
• a high temperature
• smelly discharge

This may mean you have an infection. You should also speak to your GP if you think you're pregnant.

How to tell if an IUS is 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 clinician 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 unlikely that your IUS will come out, but if you can't feel the threads or if you think the IUS has moved, you may not be fully protected against pregnancy. See your doctor or nurse straight away and use extra contraception, such as condoms, until your IUS has been checked. If you've had sex recently, you may need to use emergency contraception.

Your partner shouldn't be able to feel your IUS during sex. If they can feel the threads, get your GP or clinician to check that your IUS is in place. They may be able to cut the threads a little. If you feel any pain during sex, go for a check-up with your GP or clinician.

Removing an IUS

Your IUS can be removed at any time by a doctor or nurse.

If you're not going to have another IUS put in and you don't want to become pregnant, use another contraceptive method (such as condoms) for 7 days before you have the IUS removed. Sperm can live for 7 days in the body and could fertilise an egg once the IUS is removed. As soon as an IUS is taken out, your normal fertility should return.

Who can use an IUS?

Most women can use an IUS, including women who have never been pregnant and those who are HIV positive. Your GP or clinician will ask about your medical history to check if an IUS is the most suitable form of contraception for you.

Your family and medical history will determine whether or not you can use an IUS. For example, this method of contraception may not be suitable for you if you have:

• breast cancer, or have had it in the past 5 years
• cervical cancer
• liver disease
• unexplained vaginal bleeding between periods or after sex
• arterial disease or history of serious heart disease or stroke
• an untreated STI or pelvic infection
• problems with your womb or cervix

An IUS may not be suitable for women who have untreated STIs. A doctor will usually give you a check-up to make sure you don't have any existing infections.

Using an IUS after giving birth

An IUS can be fitted 4 weeks after giving birth or during a caesaraen section. You can discuss this with your midwife during your pregnancy. 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 doctor or nurse straight after miscarriage or abortion. Discuss this with the staff looking after you.

Advantages and disadvantages of an IUS

Advantages of an IUS are that:

• it works for 3 to 6 years
• it's one of the most effective forms of contraception available
• it doesn't interrupt sex
• it may be useful if you have heavy or painful periods because your periods usually become much lighter and shorter, and sometimes less painful – they may stop completely after the first year of use
• it can be used safely 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
• your fertility will return to normal when the IUS is removed

Disadvantages of an IUS are that:

• some women won't be happy with the way that their periods may change – for example, periods may become lighter and more irregular or, in some cases, stop completely; your periods are more likely to stop completely with a 52mcg IUS than with Jaydess
• irregular bleeding and spotting are common in the first 6 months after having an IUS fitted – this is not harmful and usually decreases with time
• some women experience headaches, acne and breast tenderness after having the IUS fitted
• an IUS doesn't protect you against STIs, so you may also have to use condoms when having sex – if you get an STI while you have an IUS fitted, it could lead to 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 uncommon
• hormonal problems can also occur

Risks of an IUS

Complications are rare.

Perforation of the womb

In rare cases an IUS can perforate (make a hole in) the womb or cervix when it's put in. This happens in fewer than 1 in 1,000 insertions. If the doctor or nurse fitting your IUS is experienced, the risk of perforation is extremely low. If perforation occurs, you may need surgery to remove the IUS.

Perforation can cause pain in the lower abdomen but is usually painless. It doesn't usually cause any other symptoms. The first sign is usually that the threads cannot be felt. Although the usual reason for this is that the threads have curled up into the cervix.

Contact your GP or sexual health if you can’t feel the threads after having an IUS fitted.

Pelvic infections

Pelvic infections may occur in the first 21 days after the IUS has been inserted. The risk of infection from an IUS is extremely small. Fewer than 1 in 100 women who are at low risk of STIs will get an infection. Contact the service who put it in for you if you have:

• an unusual discharge
• persistent abdominal pain
• bleeding

Expulsion or displacement

5 in every 100 IUS are ejected (expelled) by the womb. This is more likely to happen soon after it has been fitted. But can happen later, which is why you should check the threads once a month. Your doctor or nurse will teach you how to check the threads.

An IUS can move inside the womb. This is called displacement. This can cause spotting between periods and crampy lower abdominal pains. If you get this speak to your GP or sexual health clinic. There can be other causes which can be checked.

Ectopic pregnancy

If the IUS fails and you become pregnant, your IUS should be removed as soon as possible if you're continuing with the pregnancy. There's a small increased risk of ectopic pregnancy if a woman becomes pregnant while using an IUS, so an early ultrasound is advisable. You should contact your local early pregnancy unit or GP as soon as possible if you have a positive pregnancy test and an IUS in place. If you have an IUS and severe abdominal pain a pregnancy test should be done.

Where can you get an IUS?

Most types of contraception are available for free in the UK. Contraception is free to all women and men through the NHS. Places where you can get an IUS include:

• some GP practices – talk to your GP or practice nurse
• sexual health clinics

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 pharmacists won't tell your parents (or carer). They'll provide you with contraception as long as they believe you fully understand the information you're given and are able to use the contraception safely.

Doctors and nurses have a responsibility to make sure that you're safe and free from harm. They'll encourage you to consider telling your parents (or carer), but they won't make you. The only time that a professional will not be able to keep confidentiality is if they believe you're at risk of serious harm, such as abuse. If this was the case they would usually discuss it with you first.