Mirena is called an intrauterine system (IUS). It is made of a small plastic frame that is shaped like a T and contains a hormone cylinder. Mirena is fitted in the uterus by a trained doctor or nurse and slowly releases hormones to prevent pregnancy. The hormones in Mirena prevent sperm from passing through the cervix by making the mucus thicker and less favourable for pregnancy.
In addition to being a very effective method of contraception, Mirena can also be used to treat heavy menstrual bleeding where the cause is unknown, and may make your periods shorter, lighter and less painful. Mirena may also be prescribed for women as part of their hormone replacement therapy (HRT) to provide protection to the lining of the uterus, referred to as the endometrium.
Only trained doctors can fit or insert the Mirena. After a gynecological examination, Mirena is fitted into the uterus using a thin, flexible plastic tube that is passed through your cervix. Once the insertion tube is removed, the threads from the base of Mirena will pass through the cervix and into the vagina and are cut to about 2 to 3 cm in length outside the cervix. Some women find the procedure uncomfortable or painful. It is advisable to allow time for a short rest before you leave the clinic.
- Once Mirena is fitted, it prevents pregnancy for up to 5 years
- It can be removed at any time if you wish to stop using the method for any reason
- It’s over 99% effective at preventing pregnancy
- It may reduce your period pain
- After a few months, it may reduce menstrual flow to little or nothing so your periods are lighter and shorter than they were before it was fitted.
- It is advisable to check the threads of Mirena once a month
If you wish to discuss your suitability for Mirena or have any questions regarding this contraception treatment, our women’s health team are more than happy to help.
How does Mirena prevent pregnancy?
Mirena contains a hormone that prevents pregnancy by:
- Thickening the normal mucus in the cervical canal (opening of the womb) so that the sperm cannot enter the uterus to fertilise the egg
- Controlling the monthly development of the endometrium (lining of the uterus) so that the lining is not thick enough for you to become pregnant
- Inhibiting the normal sperm movement inside the uterus and the tubes preventing fertilisation
What happens to my periods?
Mirena will affect your periods. Initially the number of days with bleeding each month increases and most women have frequent spotting in addition to their periods for the first 3-6 months after the system is fitted. Over time, most women are likely to have a gradual reduction in the number of bleeding days and in the amount of blood loss each month. Some women find their periods stop altogether.
How long can Mirena be used?
Each Mirena is approved for up to 5 years’ continuous use for all of the indications, after which it has to be removed and replaced.
What side effects can I expect?
All medicines can have side effects and some patients may experience them while using Mirena. You should expect a change in your menstrual patterns and this is the most commonly reported side effect. The changes may initially include spotting, shorter or longer menstrual periods, irregular bleeding, heavy periods, menstrual pain, oligomenorrhea (infrequent or lighter periods) and amenorrhoea (no periods)
Some other side effects reported by women using Mirena include:
- Abdominal or pelvic pain
- Genital discharge
The Consumer Medicine Information leaflet from inside the packaging contains more information on possible side effects but always speak to your doctor as soon as possible if you do not feel well while you are using Mirena and you think it may be associated.