The IUS (Mirena) - Lloydspharmacy.com Health

Written by Dr David Delvin, GP and family planning specialist

What is the IUS?

First of all, please don’t confuse it with the IUD. The IUD is the contraceptive coil, and a major problem with it is that it tends to make your periods heavier, longer and sometimes more painful.

Term watch

The letters 'IUS' stand for 'intrauterine system' (intrauterine means inside your womb) but a lot of people refer to it by its brand name, Mirena. It has steadily become more popular during the 21st century.

This is partly because of its 'therapeutic' effect in making periods lighter.

For instance, I have seen quite a lot of women in their 30s and 40s who have been able to avoid having a hysterectomy by using Mirena.

The IUS is quite different from the IUD, because it contains a hormone. In addition to being a contraceptive, it usually makes your periods shorter, lighter and pain-free. So it’s often used in order to treat heavy periods or painful ones.

It's quite often given to post-menopausal women, in order to help them 'balance' their hormone replacement therapy (HRT).

What does it look like?

It’s not much longer than a match and is more or less T-shaped. It has a couple of short threads hanging from the foot of the 'T'. These are useful when the time comes to remove it. All the doctor or nurse has to do is to tug on them with a little clamp.

Most importantly, the stem of the 'T' contains a reservoir full of female hormone, of the type known as a 'progestogen'. This hormone is steadily released into your womb, day after day, for as long as you use the device, making it more effective in preventing pregnancies.

The IUS can last for up to five years, after that, it's 'worn out' – so you would need to have it changed.

How effective is Mirena in protecting me against pregnancy?

Very effective indeed – and better than the IUD ('coil'). Its effectiveness rate is generally reckoned to be around 99 per cent, which means that if 100 women use Mirena for a year, then only one of them would get pregnant. (Indeed, recent trials have claimed even lower failure rates than that.)

It starts to protect you against pregnancy as soon as it's been put in.

Incidentally, if you decide that you now want to get pregnant, your fertility should return immediately after the device is removed.

How does it work?

It works by thickening the mucus inside your cervix, making it very difficult for sperm to get through. Also, the hormone thins down the lining of your womb – thus making it unlikely to 'accept' an egg.

The hormone in Mirena is called 'levonorgestrel', or 'LNG'. It’s a component of several contraceptive Pills.

In some women, the hormone has the effect of preventing the ovaries from releasing eggs. (This helps to make the IUS more effective than the IUD.)

Family planning experts say that the device does not cause an abortion.

What are the drawbacks of the IUS?

Like all other methods of contraception, Mirena has its drawbacks.

It takes some months for it to establish control over your periods.
During those first few mon'ths, you're likely to have irregular (but fairly slight) bleeding – so keep pads or tampons handy.
The hormone in Mirena does get into your system, and it may cause breast tenderness though this often goes away after a few months.
The hormone can also cause acne (spots).
It can occasionally cause headaches or mood changes.
The hormone can also cause cysts on your ovaries – but these are very rarely serious, and they don't usually require any treatment. However, the latest advice says that they should be monitored by ultrasound scan.

Furthermore, the IUS can – like the IUD – occasionally:

fall out
penetrate the wall of the womb ('perforation'), especially during insertion.

You should check your 'threads' regularly to make sure the device isn't falling out. And if you ever get a lot of pain in your lower tummy – which might indicate perforation – contact a doctor.

There is a small risk of infection associated with any device that is put into the womb. Women who have many partners are most at risk.

On the internet, a surprising number of Mirena-users posted reports of hair loss. It seems quite likely that this is an infrequent side-effect of the IUS, but at present it's difficult to say how common it is.

Do we know the long-term effects of Mirena?

No, we don't. It’s only been around since the late nineties, so – to be frank – doctors have no idea what the effects of the hormone might be after another 20 years or so.

However, at the moment there are no indications that it might cause cancer or other nasty side-effects in the long term.

So what are the advantages of the IUS?

An increasing number of women like it, because:

it doesn't interfere with sex
it's so effective
you can keep it in for five years
it usually gets rid of your period pain
after a few months, it should reduce menstrual flow to little or nothing.

So Mirena is becoming more popular. In 2010, the Family Planning Association (FPA) estimated that it's used by 2 per cent of British women aged 16 to 49.

Is there anyone who shouldn’t use it?

Yes. Your family planning nurse or doctor will tell you more about this, but among those who shouldn't try Mirena are:

women with unexplained vaginal bleeding
women with pelvic infections
women with structural abnormalities of the womb or cervix
probably women with heart valve trouble – unless a specialist gives the OK
some women with systemic lupus erythematosus (SLE).

The 2011 edition of the British National Formulary says that Mirena should only be used 'with caution' in women who are prone to depression. This is because of its capacity for causing mood swings.

What do I do if I want to try the IUS?

Find a doctor who has been properly trained in how to fit a Mirena. On no account go to anyone who hasn't.

Many experts work in family planning clinics, but an increasing number of general practitioners have now been trained.

If you can't find anyone, call sexual health direct on 0845 310 1334. This is a helpline run by the FPA.

Please bear in mind that a Mirena is usually inserted within seven days after the start of a period. It can also be inserted six weeks after the birth of a baby or immediately after a termination.

Before you have the device inserted, you may well be asked to have a vaginal swab test to make sure you haven't got a chlamydia infection.

What is the insertion like?

It generally hurts a bit – less so if you've had several children. You may want to take aspirin or paracetamol beforehand. Some doctors will give you an injection of local anaesthetic.

If you search the internet at the moment, you will find that some women do complain that their insertion was very painful indeed. On the other hand, a lot of patients say that the pain was fairly slight.

Procedure: you take off everything below the waist, and lie on the clinic's couch – usually on your back. The doctor or nurse examines you internally with gloved fingers, then checks out your cervix, using a special instrument that gives a good view of it.

Then the doctor inserts the thin 'straw' that contains the Mirena – pushing it through the hole in your cervix and into your womb. That's the bit that may cause you pain.

Afterwards, you'll be asked to sit (or lie down) and rest for a while. Don’t drive yourself home. Take it easy for the rest of the evening.

It's common to get slight pain and bleeding in the next few days. But if you're concerned, don't hesitate to contact the doctor or clinic. Similarly, if you're unlucky enough to get an offensive (that is, smelly) discharge, this might indicate an infection – so seek medical help.

Sex

You can have sex whenever you like, as you are now protected. Personally, I think it’s reasonable to wait 24 hours and let the device settle down.

Your partner may possibly be able to feel the threads in your vagina, but few men complain about this.

Tampons

You can use tampons, as they shouldn't interfere with your Mirena. However, I advise patients not to use them during the first few days after insertion.

Can you use it as 'emergency contraception?'

No. Mirena is not licensed for use as an emergency or so-called morning-after contraceptive.

Last updated 06.06.2011

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