The progestogen-releasing intrauterine device – Mirena®

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A Mirena® intrauterine contraceptive device (IUD) is a small device which is fitted inside the uterus, where it releases a hormone to prevent pregnancy.

What is Mirena®?

Mirena® is the brand name for the IUD which releases a progestogen (a hormone similar to the hormone progesterone which is naturally produced by the female body). It is T-shaped, made of plastic and can prevent pregnancy for up to 5 years by steadily releasing small amounts of the progestogen directly into the uterus.

How does Mirena® work?

Once inside the uterus, Mirena® prevents pregnancy by:

thickening of the mucus of the cervix so that sperm cannot enter the uterus
changing the lining of the uterus, making it unsuitable for pregnancy

The device has fine threads attached to the lower end of it so that when it is fitted, the threads protrude through the cervix (neck of the womb) into the vagina.

These threads allow the woman to check that the device is still in place and enables easy removal of the device by a doctor.

How effective is Mirena®?

Mirena® is approximately 99.9% effective. This means that on average, if 1000 women use Mirena® for one year, it is possible that one of them may become pregnant.

What are the advantages of Mirena® as a method of contraception?

highly effective
long acting (effective for 5 years)
does not require daily pill taking or regular injections
reversible and rapid return to usual fertility
reduces amount of blood loss with periods and in some women improves painful periods
does not interfere with breastfeeding
inexpensive

What are the disadvantages of Mirena® as a method of contraception?

insertion and removal of the device can only be performed by a trained doctor
insertion requires a procedure which some women may find quite uncomfortable
bleeding patterns may become irregular and spotting and irregular light bleeding are common during the first 3-5 months after insertion
does not protect against sexually transmitted infections (STIs)

What are the possible health benefits of Mirena®?

after about 5 months nearly all women will experience light periods only
after 12 months about 20% of women will have no periods at all
can be used to treat excessively heavy menstrual bleeding once serious causes for heavy bleeding have been investigated by a doctor
reduces period pain in many women
may be suitable for women approaching menopause as it provides effective contraception and can continue to be used as the progestogen component of hormone replacement therapy

What are the possible side effects or complications of Mirena®?

Side effects of the hormone in Mirena® include:

changes in periods as above
only a very small amount of progestogen passes into the bloodstream. This means that other side effects are fairly rare, mild and often improve with time. They include acne, breast soreness, headache and mood changes. Mirena® should have no effect on weight.

Side effects and complications of the insertion procedure can include:

following insertion, some women notice abdominal cramping pain and bleeding for up to a week or two
perforation
This is a rare but potentially serious complication where the Mirena® device passes through the wall of the uterus into the pelvic area, usually at the time of insertion but can very occasionally occur later. This can occur in about one per 400 insertions. This requires surgery under a general anaesthetic to remove the Mirena®.
expulsion
Sometimes the Mirena® device may be partially or completely pushed out by the uterus. This is more common in women who have never had children. It occurs in about 5 per 100 insertions. It is important to check for the threads after each period to detect if this has occurred, particularly in the first few months after insertion.

Other considerations:

pelvic inflammatory disease (PID)
This is a rare complication of Mirena® insertion, which is most likely to occur in the first few weeks after the insertion procedure. The risk of PID is also related to exposure to sexually transmitted bacteria (chlamydia and gonorrhoea). It is important that you consider carefully your potential risk of acquiring an STI throughout the whole period of time you have the Mirena® device in place. PID may in some cases lead to infertility.
pregnancy
The chance of pregnancy is 1 in 1,000. In the rare event of a pregnancy with a Mirena® in th uterus there is a small risk of:
- miscarriage
- ectopic pregnancy
  (a pregnancy in the Fallopian tube) This is less likely to occur than with other IUDs or no contraception. Ectopic pregnancy can lead to serious pain, internal bleeding and reduced fertility.

Is Mirena® suitable for all women?

Mirena® may be PARTICULARLY SUITABLE for women who:

have heavy, painful periods
are unable to take oestrogen
wish to use an effective long-term but reversible method of contraception
have difficulty remembering to take oral contraceptives
are approaching menopause

Mirena® MAY NOT be suitable for women

who have:

unexplained vaginal bleeding (this should be investigated before using a Mirena®)
a recent history of PID
a high risk of STIs, eg currently have or are likely to have, more than one sexual partner or a partner who has more than one partner
uterine or cervix abnormalities
never had a pregnancy, particularly younger women
have difficulties with vaginal examinations and procedures

Mirena® IS NOT suitable for women who have:

recently had breast cancer
some other forms of cancer

What do I need to know about having a Mirena®?

Insertion of a Mirena® involves a procedure. Some women find insertion quite uncomfortable. This can be managed with the use of a local anaesthetic into the cervix, but occasionally for some women, a general anaesthetic is required.

The device should be inserted and removed by a medical practitioner trained in the procedure. Before a Mirena® is inserted you will be required to have an assessment by a doctor and a prescription supplied. This allows the doctor to assess your medical history and suitability for this method and to ensure that arrangements are made for insertion at the right time of your menstrual cycle. It also enables you to ask any questions you may have and be certain it is the most suitable method for you.

At the first visit, a pelvic examination, Pap smear (if due) and other tests to check for infection are performed. A second visit is arranged for insertion of the Mirena®, usually during the first seven days of a menstrual cycle.

What else do I need to know about the ongoing use of Mirena®?

Generally you are asked to attend for a follow up visit after insertion and at any time where concerns exist. The Mirena® needs to be replaced with a new device every 5 years. After 5 years, the effectiveness reduces and there is a risk of an ectopic pregnancy occurring (pregnancy in the Fallopian tube).

It is important to keep a record of the date that replacement is due and to arrange for replacement no later than this date.

The Mirena® can be removed before this date for any reason but it is important to arrange another method of contraception before the device is removed as fertility can return immediately after removal.

Where is Mirena® available?

Mirena® is available from FPQ clinics, as well as gynaecologists and some general practitioners (GPs).

www.fpq.com.au
Phone: 07 3250 0240

Disclaimer

Family Planning Queensland (FPQ) has taken every care to ensure that the information contained in thispublication is accurate and up-to-date at the time of being published. As information and knowledge is constantly changing, readers are strongly advised to confirm that the information complies with present research, legislation and policy guidelines. FPQ accepts no responsibility for difficulties that may arise as a result of an individual acting on the advice and recommendations it contains.

Funded with assistance by Queensland Health