A birth control method that's been available for 10 years in Europe and used by approximately two million women is now cleared for use in the U.S. - The Food and Drug Administration just approved Mirena, which will be available in the first quarter of 2001.
Mirena is an ideal choice in contraception for busy mothers who do not want to worry about taking pills or getting pregnant and who value sexual spontaneity.
Mirena is small, flexible and T-shaped and is inserted into the uterus
by a health care professional in just a few minutes. Mirena does not
contain estrogen. Instead, it releases a low-dose of progestin and is
better than 99% effective -- as effective as tubal ligation. Mirena
lasts for five years or until removed. Experience has proven that
Mirena may make periods shorter and lighter.
The Mirena IUS is like many other types of Intrauterine Contraceptive
Devices (IUCD's or coils) in that it is fitted by a doctor and remains
in the womb for a fixed amount of time, after which it must be changed.
It is different, however, in that it is much more effective than usual
IUCD's and avoids many of the side effects that put women off this choice
In this review the abbreviation IUCD refers to this whole group of contraceptives,
and the terms Mirena and IUS will be used interchangeably.
Most IUCD's make a woman's periods heavier, but the Mirena actually makes
periods much lighter than usual. Because of this, it is frequently used
as a treatment for heavy periods, even in women who don't need contraception.
As can be seen in the picture, it is made of a light, plastic, T-shaped
frame with the stem of the 'T' a bit thicker than the rest. This stem
contains a tiny storage system of a hormone called Levonorgestrel.
This hormone is also used in contraceptive pills such as Eugynon, Logynon,
Microgynon, Ovran 30, Ovranette and Trinordial. In the Mirena, however,
a much lower dose is released than when you take the Pill (about 1/7th
strength), and it goes directly to the lining of the womb, rather than
through the blood stream where it may lead to the common progesterone-type
side effects (see below).
How effective is the contraception?
If 1000 women used the Mirena IUS for a year, only one would fall pregnant.
This compares with about 10 for the normal IUCD, 20 for the Pill and 10-15
for the injection (Depot Provera).
Mirena acts as a contraceptive in two ways: it makes the mucus at the
neck of the womb (the cervix) much thicker, preventing sperm from
getting through and it also makes the lining of the womb extremely thin,
stopping implantation. In some women it prevents egg release (ovulation).
As with all IUCD's, if it does fail, there is a higher risk of ectopic
pregnancy (a pregnancy located outside the womb, usually in the tube).
If you felt pregnant or had a positive pregnancy test, it is important
to see your doctor to rule this out. Overall, however, compared to women
not using any contraception, the risk of ectopic pregnancy is greatly
reduced (around 2 per 10,000 women each year)
because the IUS is such a good contraceptive.
If a pregnancy does occur with an IUCD, it is advisable to remove the
contraceptive if possible - this reduces the risk of bleeding, infection
and miscarriage. Because failure is so rare, there is little information
available on the effects on an ongoing pregnancy with the Mirena still
Fitting the Mirena IUS
Before it is inserted, the doctor will do an examination to make sure
the womb is a normal size and there is nothing else unusual to find. If
there is some discharge, swabs will be taken to rule out infection before
it is placed. The IUS is inserted within a week of beginning a period
- this helps to reduce the chance of expulsion and irregular bleeding
(as the womb lining is already quite thin at this time). It may be inserted
immediately after surgical termination of pregnancy, but should be deferred
until 6 weeks after delivery of a baby.
A speculum is placed in the vagina, like when you have a normal smear
test, and the Mirena is placed into the womb through the cervix. Because
it contains the storage of hormone, the stem is slightly wider than in
normal IUCD's. This can occasionally lead to difficulties with fitting,
especially if you have not had a baby before. In this situation, it would
be helpful to use some local anaesthetic. It should be fitted by someone
who has been trained and has experience in fitting IUCD's.
It is a good idea to take some painkillers a couple of hours before the
fitting - this will help reduce any discomfort. A good choice is Ibuprofen
400 mg, which can be bought over-the-counter at a chemist. Most women
do not find the insertion procedure very uncomfortable - usually much
less than expected.
Once the IUS is in place, you won't be able to 'feel' it in your womb.
Your doctor will show you how to check for the strings, and it is very
unusual for your partner to be aware of it during intercourse. After fitting,
a further appointment should be made for six weeks later to check the
strings can still be seen. Yearly checks are advised after this appointment.
Removing the Mirena
Removal involves a speculum examination again and the IUS is removed
by pulling on the strings. This is only uncomfortable for a second or
two as it comes out. The hormone effect on the lining of the womb is reversed
within a month and normal periods and fertility returns.
Mirena for heavy periods
Although the IUS was originally developed as a contraceptive, the discovery
that it leads to much lighter periods was a great bonus. Many gynaecologists
now suggest the Mirena as a treatment for heavy periods if tablet treatment
After 3 months use, the average blood loss is 85% less, and by 12 months
the flow is reduced by 97% every cycle.
About one third of women using the IUS will not have any periods at all.
Although women initially find it a bit unusual not having periods, it
doesn't cause any problems. There is no 'build up' of blood, because the
hormone in the IUS prevents the lining of the womb from building up at
all. Often it is the excessive thickening of this lining that is the cause
of the problems in the first place.
One study looked at 54 women who had heavy periods and were awaiting
hysterectomy. They all used the Mirena,
and just under 70% were taken off the waiting list because they were happy
with the treatment. In another study of 50 similar women, 82% avoided
At present in the UK, the Mirena IUS is not officially licensed for treating
heavy periods. This doesn't mean that it is unsafe to use it, and on a
'named-patient' basis its use is very common. It is likely that this license
will be granted in the near future.
Although the IUS isn't primarily used for painful periods, two studies
that it does help in many cases (as often as 80% of the time). If painful
periods persist, it is usual to rule out any other problems with a laparoscopy.
Large fibroids are a common cause of heavy
periods. If they are so large, or in such a position that they make the
inside of the womb an abnormal shape, it is unlikely that the Mirena will
remain in place, and would not be helpful as a treatment. With small to
moderate size fibroids, it is quite reasonable to use the IUS and one
study has found that fibroids are less
common in women who use the Mirena. A further paper has found that in
the 5 women studied, a Mirena actually reduced the size of their fibroids. This is only one report, of course, and
the IUS cannot be recommended as a treatment for fibroids based on this
alone, though it is very interesting.
Premenstrual syndrome (PMS)
PMS is a syndrome that is thought to be caused by the varying hormones
of the menstrual cycle. There have been suggestions that the IUS may be
useful as it will allow a continuous dose of hormones to be given (oestrogen)
without the worry of excessive stimulation of the lining of the womb.
Usually oestrogens are combined with a course of a progestagen to prevent
this, but many women experience PMS-like symptoms with progestagens. At
present there is little published in the medical literature about the
use of the Mirena in this way, but for severe cases, where hysterectomy
is being considered as the only remaining alternative, it would certainly
be reasonable to consider this.
Hormone replacement therapy (HRT)
There is a growing experience with the use of the IUS for women who require
hormone replacement therapy, but who have either bad PMS-like symptoms
or erratic bleeding on normal HRT preparations. The IUS with continuous
implants, tablets or patches of oestrogen provides good symptom relief
with minimal side effects. As its use in this way is not generally established
in the UK, this would normally be prescribed under the care of a gynaecologist.
In other countries (eg. Finland) the IUS is licensed for use in this way
and can be routinely used for up to 5 years.
Women who have experienced an ectopic pregnancy
are at a greater risk of this happening again in future pregnancies. For
this reason, they are advised to choose a type of contraception that does
not increase this risk any further - in particular they are encouraged
to avoid IUCD's, as these are known to increase this risk. The risk of
ectopic pregnancy is very much lower with the IUS than in women not using
any contraception (60 times lower, in fact). Although perhaps not a first
choice, the IUS may be considered when other contraceptives are really
not suitable. As with most decisions in medicine, it is about the balance
Expulsion. In the early months of use, there is a very small chance
that the IUS may dislodge and come out, either in part or altogether.
This risk may be greater than with other IUCD's, presumably because it
is that bit larger. There may be symptoms such as bleeding or persistent
pain not relieved by simple pain killers, or it might be passed without
any discomfort at all. As the system reduces blood flow, sudden return
of heavy periods might suggest this has happened.
Hormonal problems. Although the IUS delivers its hormone directly
to the lining of the womb, it does lead to a slight increase in progesterone
levels in the blood stream. The levels are much lower than that found
with the progestagen-only pill (POP) and usually don't lead to side effects.
If they do occur, most often they are mild and only last a couple of months.
Side effects have included headache, water retention and breast tenderness.
Ovarian cysts. Progestagen hormones increase the chance of benign,
simple ovarian cysts. This is more common with the higher hormone levels
associated with the progestagen-only pill. Overall the risk is about 3
times higher (1.2% in IUS users versus 0.4% normally). These cysts most
often do not require any treatment and resolve on their own over 2-3 months.
It is usual to arrange follow-up ultrasound scans over this time if they
do occur. The most common symptoms of a cyst is abdominal pain that doesn't
settle with simple painkillers.
Bleeding problems. These are without a doubt the most common problem
associated with the Mirena. 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, 20% of users experience prolonged bleeding of more than
8 days duration, but by the third month only 3% have prolonged bleeding.
Pelvic infection. In general IUCD's increase the risk of infection
of the womb, tubes and other pelvic organs. Studies looking at Mirena
suggest that this may not be the case, with the IUS being protective against
infection, particularly in the age group most at risk (<25y). Although
this would fit with the thickening of the cervical mucus preventing infection
getting through the cervix, this finding is not universal in all studies.
The actual risk of infection is very low, at less than 1% with 5 years'
The IUS is an effective contraceptive and treatment for heavy periods.
It reduces menstrual pain, may be used with small to moderate fibroids
and has the potential as a treatment for severe PMS. It is associated
with a low risk of ectopic pregnancy and infection. It may be more difficult
to insert than standard IUCD's, in some women can lead to mild hormonal
effects, and commonly causes irregular bleeding in the initial months,
though this usually settles by 3-6 months. It is a particularly good treatment
choice for women with heavy periods who wish to avoid major surgery.