A Mirena IUS (Intra-Uterine System) is a small, T-shaped plastic device inserted into the womb (uterus) and subsequently slowly releases a small amount of the female hormone progestogen.
Consequently, it has the following actions:
- It thickens cervical mucus, making it more difficult for sperm to move through the cervix
- It thins the lining of the womb (endometrium), so an egg is less likely to be able to implant itself.
- It may also prevent the release of an egg each month (prevents ovulation) in some women.
Hence, by these actions the Mirena IUS is recommended and is effective for the following indications:
- Provide contraceptive to stop you getting pregnant for up to 6 years. When inserted correctly, it is more than 99% effective.
- Treat heavy and or painful menstrual bleeding for up to 5 years. In some women the periods completely stop, although in the majority, periods become much lighter. Hence surgery can be avoided
- Form the progestogen part of combined hormone replacement therapy (up to 4 years only)
- Treat or prevent endometrial hyperplasia (overstimulation of the tissue) (up to 4 years only). This indication is only used for selected “at risk” patients, after discussion.
For contraceptive purposes it is an alternative to the copper coil or intrauterine device. There also other versions of the intrauterine system which have a shorter duration of action or may not be licensed for all the same indications as the Mirena IUS.
It can usually be inserted in the outpatient department, although some patients may require insertion in theatre using a general anaesthetic, at a later date. Occasionally a Pipelle endometrial biopsy may be taken just before insertion (when used for non-contraceptive purposes).
Online References
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