The Intra-Uterine System

What is the Intra-Uterine System (IUS)?

It is a plastic “T” shaped frame about the size of a matchstick, which contains hormones and sits inside the womb. It has two strings on the end of it that travel through the cervix; this allows us to remove it and check that it is in the right place.

Why has it been suggested to me?

The IUS is different to other contraceptive coils as it usually makes periods lighter than usual. Many patients have spotting or irregular bleeding for the first 3-6 months, others will have prolonged heavy bleeding. In a third of people their periods stop all together without any problems. There is no build-up of blood because the hormone in the coil prevents the lining of the womb from building up at all, so it remains thin.

Studies have looked into people who have had such heavy periods that they were thinking of having a hysterectomy. One study showed that two thirds of people who were booked in to have a hysterectomy cancelled their operation after having the IUS fitted.

The IUS has also been shown to reduce painful periods in up to 8 out of 10 women, reduce physical symptoms of PMS (premenstrual symptoms), shrink fibroids as well as providing contraception.

How does it work?

The IUS contains the hormone progesterone, which is released slowly over 5 years. This hormone prevents the lining of the womb building up and, therefore, usually reduces the amount of bleeding.

Will it work for me?

7-8 out of 10 people are happy with the IUS. It is recommended to keep the IUS in for at least 6 months to see what will happen with your bleeding pattern.

How is it put in?

Before it is inserted, your doctor will carry out an examination to make sure that your womb is a normal size and there is nothing unusual to find. The IUS is inserted within a week of starting your period – this helps reduce the risk of expulsion (the coil falling out) and irregular bleeding. A speculum (an instrument that helps us look at the neck of the womb (cervix) is placed in the vagina, rather like having a smear test and the IUS is placed into the womb through the cervix.

Will it hurt?

It is a good idea to take some painkillers before the fitting to reduce any discomfort. Most people do not find the insertion very uncomfortable – usually much less than they expected.

Will I feel it in my womb?

For a few days after its fitted you may have some mild period like pains. Once the IUS is in place, you and your partner will not be able to feel it in your womb.

How will I know it’s still there?

Your doctor will show you how to check for the strings of the coil. Around 6 weeks after the fitting you should make an appointment with your GP to check that the strings can be seen. Yearly checks are advised after this.

What if I change my mind?

Removal involves a speculum examination again and the IUS is removed by pulling on the strings. This is only uncomfortable for a few seconds as it comes out.

How long will it last?

The progesterone hormone in the IUS will last for 5 years. If required, a new one can be fitted at the same time that the old one is removed.

How long do I wait to decide if it works for me?

It can take up to 9 months for the IUS to work fully.

What are the disadvantages?

Will it fall out?

In the early months of use there is a small chance that the IUS may dislodge and come out. As the system reduces blood flow, a sudden return of heavy periods might suggest that this has happened.

Will I have irregular bleeding?

This is without a doubt the most common problem associated with the IUS. It takes about 3 months for the lining of the womb to thin down and during this time, bleeding can be erratic or even heavy at times, but almost always settles after 3-6 months.

During the first month, 2 out of 10 users experience prolonged bleeding of more than 8 days, but by the third month only 3 out of 100 have prolonged bleeding. Some people experience persistent spotting which may not settle.

Will my hormones be affected?

Although the IUS delivers its hormone directly to the womb’s lining, it does lead to a slight increase in progesterone levels in the blood stream. These are lower than that found in the progesterone only contraceptive pill (mini pill) and do not usually lead to any side effects. If they do occur, they are usually mild and only last a few weeks. The most common side effects include headaches, water retention, breast tenderness or acne.

Will it affect my ovaries?

Progesterone hormones increase the chance of simple ovarian cysts by up to 3 times. These cysts most often do not require any treatment and resolve on their own over 2-3 months. The most common symptom of a cyst is abdominal pain that does not settle with simple pain killers.

Will it increase the chance of infection?

The infection risk is only increased in the first 20 days after insertion. After this time the IUS, unlike other contraceptive coils, has some protective effect against pelvic infection. You may be asked if you wish to have swabs for infection taken before you have your IUS fitted.

Do I need to use any contraception with the IUS?

The IUS is more effective than being sterilised, but once it is removed you can become pregnant again.


NHS Choices… (accessed April 2021)

If you or the individual you are caring for need support reading this leaflet please ask a member of staff for advice.

How to contact us:

Cotswold Ward (24 hours)
0117 414 6785
Cotswold Centre Outpatients
Mon - Thurs 0900-1700
Friday 0900-1200

0117 414 6769

© North Bristol NHS Trust. This edition published April 2021. Review due April 2023. NBT002449

The Intra-Uterine System