E F Nigel Holland
Consultant Gynaecologist and Obstetrician
Menu Patient Leaflet 4 - Mirena Coil, the treatment for heavy periods - Back to List

The MIRENA IUS (Intrauterine system) is a small plastic
T-shaped device containing the progestogen hormone levonorgestrel. It is fitted into the womb where it releases
the hormone slowly and steadily over a period of five years. The device can be inserted as an outpatient in the clinic, or under   general anaesthetic at the same time as a D&C and hysteroscopy (see leaflet 2)

- The Mirena IUS was developed as contraceptive, but it is also very effective at reducing menstrual bleeding. For this reason, it can be used as a treatment for heavy periods and helps many women to avoid surgery to remove the womb (hysterectomy).

- The Mirena IUS can also be used in Hormone Replacement Therapy (HRT) to provide the progestogen needed to protect the lining of the womb (endometrium) to avoid abnormal cells developing.

- It is licensed for 5 years after which it must be removed and may be replaced with a new device.

How does the Mirena Coil work?

The hormone in the Mirena IUS makes the lining of the womb very thin. This means there is very little to come away at period time.

- The IUS as a Contraceptive.
The failure rate is 1 in 500 women per year, compared to female sterilisation 1-3 per 1000. It works because it thickens cervical mucus so that it is difficult for sperm to get through to reach the egg. In some women it stops the ovaries from releasing an egg. It also acts as a foreign body in the womb affecting implantation of the fertilized egg.

How efective is the Mirena Coil for reducing menstrual loss?

In the long term, most women notice a marked reduction in their menstrual flow. Some women find their periods stop altogether. This is more likely to happen as you approach the Menopause and is nothing to worry about. After 5 years 35% of women will be period free and 56% will only have occasional bleeding. Around 2 out of 3 women will avoid surgery such as hysterectomy.

Are there other possible benefits?

  • Period pain is often reduced.
  • In some women the Mirena IUS will help reduce symptoms of PMS.
  • The IUS may also shrink some fibroids.
  • Reduces the incidence of pelvic inflamatory disease (PID).
  • If the mirena is removed, your periods will return to their previous pattern unless you have become menopausal. You will not have five years of periods all at once!

Can the Mirena be used for HRT?

Oestrogen, the main hormone used in HRT makes the lining of the womb thicker. A progestogen is needed to stop this happening and the Mirena does this very effectively. Bleeding is uncommon after one year and the oestrogen can be taken by any favoured route. This is particularly useful for women with bleeding problems on HRT or with side-effects of progestogens who wish contraception.

Are there any disadvantages?

It is usual to have irregular bleeding, spotting and prolonged lighter periods during the first 3 months. This usually settles down by 6 months.
- Red or brown spotting can occur but this is normal and nothing to worry about.
- Occasionally women may experience breast tenderness, which will usually resolve in time. It may be helped with Evening primrose oil, or additional short term treatment may be required.
- Other side effects may include slight weight gain, greasy skin or mood changes. These are common to all progestogens but are less likely to occur with the IUS.

If you have any further questions please do not hesitate to ask them.

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