Mirena/IUS (Intra-uterine system)

The pros and the cons of Mirena/IUS

How does it work?
The brand name for the IUS is Mirena. It is the same shape as the coil, but don't be fooled, it's a totally different animal. The coil can cause heavy periods whereas the IUS started life as a treatment of them.

It makes the lining of your womb thinner so it is less likely to accept a fertilised egg; It also makes it difficult for sperm to move through the cervix by thickening the mucus and in some women it stops the ovaries releasing an egg (ovulation), but most women who use an IUS ovulate.

The IUS can be fitted any time in your menstrual cycle if it is certain that you are not pregnant. If it is fitted in the first five days of your menstrual cycle you will be immediately protected against pregnancy. If it is fitted at any other time, you will need to use an extra contraceptive method for the first seven days.

You can go to a family planning clinic, sexual health clinic or a general practice. Some doctors and practice nurses will fit the IUS, but not all so do check.

Fitting an IUS takes about 15–20 minutes. It can be uncomfortable or painful for some women, and you might want to have a painkiller or a local anaesthetic. Your doctor or nurse should talk to you about this beforehand. You may get a period type pain and some light bleeding for a few days after the IUS is fitted. Painkillers can help with this.

Is it effective?
The IUS is over 99% effective. This means less than one woman in every 100 women who use the IUS will get pregnant in a year.

Why should I get it?
It works for five years
It doesn't interrupt sex
Your periods usually become much lighter and shorter, and sometimes less painful. They may stop completely after the first year of use. An IUS can be useful if you have heavy, painful periods
It can be used if you are breastfeeding
It is not affected by other medicines
Your normal fertility returns quickly when the IUS is removed

Why shouldn't I get it?
Your periods may change in a way that is not acceptable to you
Some women develop small fluid-filled cysts on their ovaries. These are not dangerous and do not usually need to be treated. Often there are no symptoms, but some women may have pelvic pain. These cysts usually disappear without treatment
Other side-effects may include acne and headaches. Some women report having breast tenderness
The IUS does not protect you from sexually transmitted infections, so you may have to use condoms as well. If you get an infection when an IUS is in place this could lead to a pelvic infection if it is not treated.

For further information visit www.fpa.org.uk

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