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Confused by coils? The Mirena coil can be used as hormone treatment (HRT), contraception and to control bleeding but is the Mirena right for you?
- The Mirena coil contains a synthetic progestogen called levonorgestrel
- The Mirena can be used as the progestogen part of HRT (although it is not progesterone)
- It is an effective contraception and can treat heavy, painful periods
First of all, let’s clarify what is the Mirena coil is exactly.
There are two main types of coil: the “hormonal” coil, which is known as an intrauterine system (IUS) and is a plastic T-shaped device, and the intrauterine device (IUD), which is made of copper and plastic.
The Mirena is usually referred to as a “hormonal” coil yet it does not contain a hormone! It contains a synthetic progestogen, meaning that the pharmaceutical company make a chemical with a different chemical structure to progesterone, so it works differently in your body and brain to progesterone.
Other types include Levosert, Benilexa, Kyleena and Jaydess. The Mirena coil is very small and is inserted into your womb (uterus) where it gradually releases a synthetic progestogen called levonorgestrel into your womb. Some of this synthetic hormone enters your blood vessels in your womb and then circulates around your body and brain.
There are two threads attached to the Mirena coil that pass out through the neck of your womb (cervix) and lie in your vagina. These allow you to check the coil is still there. They also mean it can be easily removed. They do not hang outside your body and your partner does not usually feel them during sexual intercourse.
RELATED: Coils for contraception: what you need to know
How does the Mirena coil work and what are the benefits?
The Mirena as part of hormone treatment (HRT)
Hormone treatment (HRT) is the first-line treatment for women experiencing perimenopausal and menopausal symptoms and for women having symptoms due to a hormonal imbalance. Your body produces less progesterone during perimenopause and menopause.
Although some people think that the Mirena coil replaces this progesterone, this is not correct as it is providing your women and body with a progestogen (a synthetic version of progesterone).
Taking estrogen in HRT can cause your womb lining (endometrium) to thicken. The synthetic progestogen works to prevent this thickening occurring. For some women, this synthetic progestogen can partially stimulate the progesterone receptor, meaning some women actually feel better when a Mirena coil is inserted. However, for other women, this synthetic progestogen blocks the progesterone receptor and reduces estradiol and testosterone in your body and brain so can make symptoms worse.
RELATED: Natural progesterone: what mental health benefits can it bring?
In contrast, progesterone capsules (such as Utrogestan) and progesterone pessaries (such as Cyclogest) have the same chemical structure as the progesterone your body naturally makes and can reduce inflammation, relax muscles, improve sleep and symptoms of anxiety. Progesterone also has other health benefits, which you can read about here.
Increasingly, women are prescribed progesterone as well as having a Mirena coil.
A treatment for heavy and painful periods
During perimenopause, it can be common for women to experience heavy bleeding [1]. Heavy periods can cause disruption, distress and difficulties in every area of life, including work, exercise, social life and sex life.
The Mirena is recommended as a first‐line treatment for heavy bleeding by NICE [2] because the low dose of progestogen controls the development of the lining of the womb – it makes it thinner, which usually leads to periods becoming lighter and shorter or stopping. One study found that the levonorgestrel-releasing IUS (such as Mirena) can reduce blood loss by more than 90% over 6 months for most women with heavy menstrual bleeding [3].
However, many women find that their bleeding improves when they are prescribed bioidentical progesterone such as Utrogestan so it may be worth considering this as a safer option.
RELATED: Heavy periods during perimenopause: what you need to know
A very reliable contraceptive
The Mirena thickens the cervical mucus, making it difficult for sperm to get to the egg, and keeps the lining of the womb too thin to support a pregnancy. It’s therefore a highly effective form of contraception – it is over 99% effective [4].
The Mirena can stop ovulation – research has shown that within the first year of Mirena use, 45% of menstrual cycles were ovulatory (after four years, 75% of cycles were ovulatory) [5,6].
RELATED: Contraception during perimenopause: HRT, the pill and the Mirena coil
What are the side effects of the Mirena coil?
The Mirena coil can cause some irregular, light bleeding. It can lead to spotting or having a brown discharge that may continue for up to six months. After this time, it usually settles down and then there is usually no further bleeding.
It used to be thought that a hormonal IUS worked only locally – in the womb – but research has shown that there is significant absorption of the synthetic progestogen, levonorgestrel, through the bloodstream into the whole body, even within 15 minutes of it being inserted. This means there is potential for side effects across the whole body.
Some women experience side effects such as acne, weight gain, hypertension, fluid retention, headaches and abdominal pain [7]. Other possible side effects include ovarian cysts and a small chance of getting recurrent thrush [8].
Some women find that having a Mirena coil worsens their mental health leading to symptoms of low mood, anxiety and poor sleep.
If you have a progestogen intolerance or sensitivity, you may prefer to take progesterone (such as Utrogestan), which has the same chemical structure as the progesterone your body naturally makes and is less likely to cause a negative reaction.
RELATED: Non-hormonal contraception: what’s right for you?
What are the risks of having a Mirena coil?
Alongside potential side effects, there are a few risks associated with use of the Mirena coil. These include:
- Pelvic infection, usually within 3 weeks of having an IUS fitted
- Ectopic pregnancy if the IUS fails
- A small increased breast cancer risk (14 extra cases of breast cancer per 10,000 women) in women aged 15 to 49, compared to those not using contraceptive medication [9]. By way of comparison, the contraceptive pill is thought to be linked to less than 1 in every 100 breast cancer cases in the UK [10].
A recent study found that there is a small risk of meningioma (benign brain tumour) in women who use the Mirena coil [11]. There is very little data available on other long-term effects of the Mirena coil.
How long does the Mirena coil last?
The amount of time a Mirena coil can be left in place depends on its reason for use.
If you use the Mirena for contraception only, it is licensed for eight years. If you use the Mirena purely for heavy menstrual bleeding, it is licensed for five years.
If you are using the Mirena for endometrial protection as part of your hormone treatment (HRT), it can be used for five years before you need to get it replaced. While the product license for Mirena is for four years for endometrial protection, the Faculty of Sexual & Reproductive Healthcare supports its use for five years.
Are there any alternatives to the Mirena coil?
There are other types of IUS (such as Kyleena and Jaydess) that can be used for contraception only, not as a part of hormone treatment (HRT). They do not contain enough progestogen to protect the womb lining.
There are other IUSs which, like the Mirena, also contain 52 mg of levonorgestrel (Benelixa and Levosert). The CoSRH supports the use of these coils for protection of the womb lining as part of an HRT regimen for five years as well as the Mirena.
There are also types of coils (IUD) that do not contain any hormones. Whilst these can work well for contraception, they cannot be used to protect the lining of your womb as part of hormone treatment; they also do not lead to periods reducing or stopping.
Bioidentical progesterone (such as Utrogestan) can be used as the progesterone part of hormone treatment.
Mirena coil fitting: your questions answered
Where can I get a Mirena fitted?
In the UK, you can usually get a Mirena coil fitted at your GP surgery, sexual health clinic or menopause clinic. Newson Clinic offers a coil-fitting service by healthcare professionals who have been specially trained to fit coils.
What are the risks of having a Mirena coil fitted?
There are very few risks associated with insertion of the Mirena coil. These include:
- In a small number of women there can be difficulties with the insertion of the Mirena coil. This can be due to uterine malformation such as a bicornate uterus (heart-shaped uterus), large fibroids distorting the shape of the womb or a narrow entrance to the womb (cervical canal). On rare occasions it may not be possible to fit the device within a clinic, so alternative options will be discussed with you.
- Very rarely (in about 1-2 in every 1,000 cases), during insertion the Mirena coil can make a tiny hole in your womb called a perforation and an operation may be needed to remove the coil [12].
- Occasionally the Mirena coil may fall out of your womb (expulsion). This happens in approximately one in 20 women [13].
How can I prepare for having a coil fitted?
You do not need any special preparation beforehand, although Dr Clair Crockett, GP and women’s hormone specialist at Newson Clinic recommends that you take a painkiller (for example paracetamol or ibuprofen) around one hour before your appointment time.
To ensure that there is no risk of pregnancy before having a coil fitted, ensure that you use adequate contraception or do not have sexual intercourse between your last period and having the coil fitted.
What will happen at my fitting?
‘You will usually be asked to sign a consent form,’ says Dr Clair. ‘This states that you agree to have the coil inserted and you understand what it involves. The clinician fitting the coil will spend time talking you through what is in the form and give you opportunity to answer questions.’
How is a coil fitted?
‘Much like when you have a cervical smear test, you will be asked to lie on an examination couch and a speculum will be used so as the clinician fitting your coil can see your cervix,’ explains Clair. ‘At this point, you should be offered a form of local anaesthetic, which will be applied.
‘A small measuring device is passed through your cervix and into your womb. This measures the length of your womb to ensure that the coil is fitted correctly. The coil is then passed into your womb within a small tube (an introducer), and the coil is released once it’s in the correct position. The introducer is removed, and the threads of the coil are then visible in your vagina. These are trimmed so they fit neatly, without you being able to feel them unless actively seeking to.’
Is having a Mirena fitted painful?
While many women do not feel any pain when having a coil inserted, most do find it uncomfortable. You can expect some period-like cramping during and after the fitting. Sometimes this can be quite severe around the time of the fitting, but is usually very short lived.
Remember, you can take paracetamol and ibuprofen an hour before the fitting, and you should ask your clinician about numbing cream or local anaesthetic spray, gel or injection. You can also ask to pause or stop the fitting at any time.
When happens after it’s fitted and when does a Mirena coil start working?
When you leave the clinic, you can return to your normal activity. You should not use tampons for the next four weeks.
If you are using the Mirena coil or another IUS for contraception, it will be effective seven days after insertion (use alternative contraception before then). A non-hormonal (copper coil) is effective immediately.
If you are using a Mirena coil for endometrial protection as a part of your HRT, then it will be effective immediately.
You may experience some bleeding, which is normal. It can take 3-6 months before you see your bleeding pattern stabilise and for periods to lessen or stop.
If you have period pains, you can take painkillers, such as paracetamol or ibuprofen. ‘If pain is not relieved by painkillers, or you are continuing to experience pain more than a week after the coil was inserted, I would advise that you see your GP or contact the clinic where the coil was fitted for advice,’ says Dr Clair.
Can the Mirena coil move?
It’s not common for the Mirena to move out of position but it is possible and this usually occurs within the first few months after insertion.
Will I have a follow-up appointment?
Most women do not need a follow-up appointment. ‘In the past it was common practice to be invited for a coil check after six weeks, however, this is no longer recommended routine practice as most women will be able to feel their coil threads when they insert a finger into their vagina,’ says Dr Clair.
‘If the coil threads are felt, and there is no ongoing pain, then this would suggest all is well. However, if you would like a review appointment to have a coil check then this can be arranged on request.’ This will involve passing a speculum to check the coil threads can be seen, which confirms the coil is in position.
How do I get a Mirena coil removed?
The healthcare provider who inserted your coil or another healthcare provider can remove it. Removal is usually very quick and painless – your healthcare provider will pull on the strings and may ask you to cough to help ease the coil out.
It is not advisable to remove the coil yourself – this can be difficult and it is important that you have appropriate advice and an opportunity to discuss the pros and cons of removal for your individual circumstances.
Newson Clinic offers coil fitting and coil removal services.
RELATED: The Mirena coil: your FAQ
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