Patient Information - The intra-uterine system (IUS) or Mirena
The intra-uterine system (IUS) or Mirena
Patient information leaflet
Gynaecology
Darent Valley Hospital
Darenth Wood Road
Dartford
Kent
DA2 8DA
01322 428100
Author:Mary Dufie
Role:Endometriosis CNS
Information accurate at time of going to print.
This leaflet aims to answer your questions about having the intra uterine system (IUS), known as Mirena, inserted. It explains the benefits, risks as well as what you can expect when you come to hospital.
What is the IUS?
The IUS is a small plastic T-shaped device that is inserted into your uterus (womb). Unlike a standard IUCD (intra uterine contraceptive device) or coil, it does not contain any copper, but has a hormone called levonorgestrel (a type of progesterone) around the central section. This hormone is released slowly into the womb to prevent pregnancy. It has two very fine threads that come through the cervix (neck of the womb) opening and rest at the top of the vagina, so that it can be checked and also so it can be removed when necessary.
What is the IUS used for and what are the benefits?
The IUS has a number of uses, including the following:
- It is widely used as a reversible contraceptive, and can be left in place for up to five years. It can be a long-term alternative to sterilisation as only two in 1,000 women using it will get pregnant.
- It is used as a treatment for heavy and painful periods and can reduce period bleeding by up to 90% (see our leaflet on Heavy periods). It can be left in place for five years, or longer if you are over the age of 45 when it is inserted.
- It can be used with oestrogen as part of hormone replacement therapy (HRT) and can be in place for up to four years.
The IUS can be inserted for other conditions that your doctor or nurse may discuss, but these will be on an individual basis. What are the risks?
There are very few risks associated with insertion of the IUS:
- In a small number of women there can be difficulties with the insertion of the IUS. It may not be possible to fit it within the outpatients department so you may need to be admitted to hospital and have it fitted under general anaesthetic.
- Occasionally, during insertion, the IUS can make a small hole in the womb called a perforation (in about one in every 800–1,000 insertions) and an operation may be needed to remove the IUS.
- Occasionally the IUS may fall out of your womb (expulsion). This happens in six to eight women in 100 and puts you at risk of pregnancy if you are using it as a method of contraception.
The IUS can cause some irregular bleeding. This is usually not heavy, but is often persistent spotting or brown discharge that may continue for up to six months. After this time it should settle down into lighter periods, and some women (about 20%, or one in five) have no bleeding at all by the end of the first year.
Are there any side effects?
Side effects are more common within the first few months of the IUS being inserted and generally settle after continued use. These may include breast tenderness, headaches, acne and symptoms similar to pre-menstrual syndrome (PMS).
Occasionally, women may develop functional or simple ovarian cysts (small fluid filled sacs on the ovaries), which are not dangerous. These usually cause no symptoms and will go away on their own.
What happens during the IUS fitting?
Fitting the IUS generally takes place in the outpatient department. However, it can be done under anaesthetic if it is necessary, or if you are having other procedures at the same time. A speculum is inserted in the same way as when you have a smear test, and the neck of the womb is cleaned. A small instrument is then gently inserted into the womb to measure the length of the womb.
It may be necessary to give a local anaesthetic of either a gel or an injection. It may also be necessary to attach an instrument to the neck of the womb to stabilise it, which may cause pain for a few seconds. The cervical canal that leads to the womb will be gently opened and then the IUS will be inserted. When this is inserted you may feel a sharp pain. After the procedure, you may feel like you have period pain for a few hours.
Will I feel any pain?
You may feel pain during and after the fitting. We would suggest that you take some painkillers that you would normally take for period pains about an hour before you have the IUS fitted.
What happens after the procedure?
After the IUS is inserted, you will see the nurse or doctor who fitted the IUS and then you will be able to go home. You may have some cramps and slight bleeding after the procedure.
What do I need to do after I go home?
When you leave hospital you can return to your normal activity. We would suggest that you do not use tampons for the next four weeks and do not have sexual intercourse for a few days. If you are using the IUS for contraception it will be effective seven days after insertion, so additional contraception (such as condoms) will be needed if you have sexual intercourse in the first week. You may experience some bleeding, which is normal. If you have period pains you can take your usual painkillers.
If you have severe pain, have an offensive or smelly discharge, or experience heavy bleeding, please contact your GP.
Further information can be obtained from NHS Direct, Telephone: 111 or go to www.nhsdirect.nhs.uk
This leaflet has been developed in partnership with the Patient Information Group and our DGT Patient Partners
Patient Information
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Reference Number:
First published: Last Reviewed: Next review date:
05/2023 05/2026