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Written by Dr David Delvin, GP and family planning specialist
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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.
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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.
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The IUS is quite different to 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 period
problems.
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.
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It takes some months for it to establish control over your
periods.
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During those first few months, you’re likely to have irregular
(but fairly slight) bleeding – so keep pads or tampons handy.
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The hormone in Mirena does get into your system, and it may
cause breast tenderness though this often goes away after a few months.
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The hormone can also cause
acne
(spots).
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It can occasionally cause
headaches or mood
changes.
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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
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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 had many partners are most at
risk.
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 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:
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it doesn’t interfere with sex
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it’s so effective
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you can keep it in for five years
-
it usually gets rid of your period pain
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after a few months, it should reduce menstrual flow to little
or nothing.
So Mirena is becoming more popular. In 2008, the
Family Planning
Association (fpa) estimated that it’s used by 2% 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:
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women with unexplained vaginal bleeding
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women with pelvic infections
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women with structural abnormalities of the womb or
cervix
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probably women with heart valve trouble – unless a specialist
gives the OK.
Not many young women use the IUS; it's really more suitable for
people who’ve had children.
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, then ring the
fpa helpline on 0845
310 1334.
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.
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
their gloved fingers, then checks out your cervix, using a special instrument
that gives a good view of it.
Then they insert the thin ‘straw’ which 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. 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 (ie 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.
Tampons
You can use tampons, as they won’t interfere with your Mirena.
However, I advise patients not to use them during the first few days after
insertion.
Can you use it a ‘emergency contraception?’
No. Mirena is not licensed for use as an
emergency ‘morning-after’
contraceptive.
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Last updated 18.08.2008
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