Reviewed January 2020

Mirena coil (IUS)

Mirena coil (IUS)

Written by Monica Karpinski, medically reviewed by Dr. Diana Chiu

Skip to:

| | | | | | |

Read more:

Is the Mirena coil right for me? | How will I know if my Mirena coil has stopped working? | Can the Mirena coil help with heavy bleeding? | Pregnancy symptoms with the Mirena coil: should I worry?

If you are interested in long-lasting contraception that doesn’t require you to take a pill every day, the Mirena coil may well be worth considering. The Mirena is a type of intrauterine system (IUS) that is placed inside the womb. It is a small, T-shaped device, and the diameter of the tube used to insert it is just 4.40mm1 — the size of the top of a pushpin. The name ‘Mirena’ is a brand name, given by its manufacturer Bayer Healthcare. Medically, the Mirena is classified as a ‘levonorgestrel intrauterine system’ (LNG-IUS), which are hormone releasing devices, and is one of four LNG-IUS available in the UK.

The Mirena coil is inserted into the womb through an insertion tube and is active for five years, but there is evidence to suggest that it may be effective for longer.2 However, the Mirena is licenced for five years of use, which means that unless there is another reason for your coil to be taken out early, it should be replaced after five years.

While the Mirena is over 99% effective when inserted correctly,3 it may not be suitable for everyone. For example, if you currently have or have had breast cancer in the last five years, or a history of serious heart disease.4

How the Mirena coil works

Once it is inserted into your womb, the Mirena releases a type of progestogen called levonorgestrel. Progestogens are steroid hormones that exhibit progestational activity5 — that is, activity that might precede pregnancy or gestation.

The released levonorgestrel works to thicken the mucus in the cervix, which makes it difficult for the sperm to pass into the womb to fertilise the egg.6 Levonorgestrel also causes atrophy, which keeps the lining of the womb thin, and suppresses the production of large, dilated blood vessels required for an egg to successfully implant.7

The Mirena also causes what is known as a ‘foreign body’ effect, which means that the body reacts to its presence by causing a local inflammatory reaction, which also may work towards preventing pregnancy.8 Most women (75%) who use LNG-IUS will continue to ovulate.9

How effective is the Mirena coil?

The Mirena coil is highly effective and has been found to have a lower rate of pregnancy than the copper coil (IUD).10 It is over 99% effective — in a 2004 Cochrane Review of over 61,000 users, there was less than one pregnancy (0.06) per 100 women in one year of use.11

Who is the Mirena coil suitable for?

It is safe for most, but not all, women to use the Mirena coil. It can be inserted at any time during your monthly cycle.

Criteria for the whether or not the Mirena is safe for use with certain conditions is defined by the UK Medical Eligibility Criteria (UKMEC), a set of guidelines that support clinicians in the UK in providing evidence-based care when it comes to contraception. As per these criteria, some conditions are considered to represent too great a health risk to be recommended. These include:12

  • Sepsis following giving birth (postpartum sepsis)
  • Sepsis following an abortion (post-abortion sepsis)
  • Current or a history of breast cancer
  • Endometrial or cervical cancer
  • Active or recurrent pelvic inflammatory disease
  • Sexually-transmitted infections (STIs) — however, the Mirena can be inserted before STI tests have been received if you are asymptomatic
  • Abnormal and undiagnosed vaginal bleeding
  • Pregnancy — you cannot have the Mirena inserted if you are pregnant13

In some instances where the risks of using the Mirena are considered to outweigh the benefits, you may still be able to have the coil inserted under particular circumstances, as per expert clinical judgement.14 If any of the below conditions or scenarios are relevant to you, it is essential that you see your doctor for assessment. These include:

  • Certain complications from organ transplants, including graft failure and rejection
  • Certain cardiovascular conditions, including stroke; a history of, or current, ischaemic heart disease; and long QT syndrome
  • A womb abnormality
  • Certain liver diseases, including severe cirrhosis

What’s it like having the Mirena coil inserted?

Your doctor should take your full medical history before recommending you for the Mirena coil, including a screening for STIs. However, if you have been screened for STIs but haven’t yet received the results and aren’t exhibiting any symptoms, you can still have the coil inserted.15 If required, you can be treated for the STI once you receive the results.

If you do have symptoms of an STI and/or pelvic inflammatory disease (PID), it is recommended that you delay the insertion of the coil until your condition is confirmed and has been treated.

If you have heavy periods, your doctor may also do a blood test or ultrasound, especially if other treatments to manage your heavy bleeds haven’t been effective or if you are at risk of other gynaecological diseases, before a Mirena will be recommended.16

The appointment for having the coil inserted should take less than 30 minutes, with the actual insertion itself taking no longer than five minutes. Your doctor or nurse will first talk you through the procedure before examining inside the vagina to check the position and size of the womb. Your doctor will perform any necessary tests, including for infection, during your appointment and prior to insertion. For insertion, the vagina is held open in the same way as during a smear test — inserting a speculum into your vagina and then gently opening it.

Experiences of pain and discomfort vary between women. While some women report excruciating pain, others describe the insertion as “uncomfortable” or “unremarkable”

The IUS is then inserted into the womb using an insertion tube. The Mirena is T-shaped, and the horizontal arms are folded and placed inside the tube. Once the Mirena has been inserted, the tube will be removed. The Mirena has two thin threads that will hang down from the bottom of the device and into the top of your vagina, and your doctor or nurse will explain how to feel for these threads to make sure the device is correctly in place.

Some women report taking painkillers prior to the insertion, however, there is no evidence from current trials that support use of painkillers to reduce pain during insertion.17 Local anaesthetic is not routinely required for insertion but is available if there are difficulties in inserting or removing the IUS.18 Around a quarter or UK health professionals regularly use local anaesthetic for insertion, with another quarter either never or rarely offering it.19

Still, experiences of pain and discomfort vary between women. While some women report excruciating pain, others describe the insertion as “uncomfortable” or “unremarkable”. Insertion is quick and whatever pain you experience should not last long.

What’s it like having the Mirena coil removed?

There are many reasons why you might want to have your Mirena coil removed. For one, you may have decided that you would like to get pregnant, or you may find the side effects too troubling. You may have also had the Mirena in for five years, which means that it’s time for you to replace it.

Many women report that the removal procedure is much easier and simpler than insertion. Your doctor or nurse will grasp the threads of the device with forceps and gently give them a pull. If the IUS doesn’t come out this way, you may be referred to have an ultrasound to help your doctor locate the device. They may then try to grasp the device and pull it out — small studies have shown that having the ultrasound as a guide is effective and can reduce the need for surgical removal.20

If the strings of your IUS are visible, then it is easier to remove it. However, if the strings are not visible and all other methods have failed, you may be referred for a hysteroscopy: a procedure where a narrow telescope with a light and camera are passed into your womb through your cervix.
This allows your doctor to examine the inside of your womb to locate the coil and then to remove it using forceps. Hysteroscopic-guided removal is considered a superior and safe option to surgical removal, where ultrasound-guided removal has failed.21

It is possible to get pregnant as soon as the Mirena is taken out, so be sure to use alternative contraception if this is not what you want

Depending on your situation, your doctor may also discuss surgical options for removal with you. They will discuss each procedure they suggest in depth with you, and make sure that it is suitable before recommending it. For example, when considering a hysteroscopy, your doctor will consider whether you have had any previous traumatic experiences that may make the procedure difficult for you.22

It is possible to get pregnant as soon as the Mirena is taken out, so be sure to use alternative contraception if this is not what you want.

Benefits of the Mirena coil

The decision to use the Mirena coil is different for every woman, who may value the various pros and cons differently. While it’s true that the Mirena can cause some side effects, there are also some notable benefits to the method.

Endometrial and other cancer protection

The Mirena coil has been found to have a protective effect on the lining of the womb (endometrium) from the stimulating effects of oestrogen, which prevents and causes regression of a condition called endometrial hyperplasia,23 where the endometrium becomes abnormally thick. This condition is not cancer, although women who have it may have an increased risk of developing womb cancer.24

There is currently insufficient evidence to recommend its use as treatment for endometrial hyperplasia, but the Mirena is licensed in the UK for protection against endometrial hyperplasia in conjunction with oestrogen replacement therapy for up to 5 years.25

Period and pelvic pain

While in some women the Mirena coil causes pain and cramping, in others, it has been shown to reduce period pain, along with pain due to endometriosis and adenomyosis.26 There are a few theories as to why the Mirena can work to relieve endo pain: one is that it works to deplete the oestrogen and progesterone receptors in the endometrial tissue outside of the womb (so making it less ‘reactive’), and another is that, among other things, its effects on the actual lining of the womb prevent the growth and multiplication of cells (‘anti-proliferative effect’).27

Heavy periods

The Mirena coil is actually licenced as a treatment for heavy menstrual bleeding and is recommended as a first-line treatment within the National Institute for Health and Care Excellence (NICE) guidelines28 — national evidence-based recommendations for clinicians and other healthcare professionals. A Finnish study of 236 women in 2001 found that women with heavy menstrual bleeding had a significant improvement in their health-related quality of life due to using the Mirena.29 Even women with heavy periods associated with fibroids (benign growths in uterine lining) have been shown to have lighter periods with mirena coil. (REFERENCE: Agarwal. 2004. Mirena IUS, a novel therapeutic alternative to hysterectomy for menorrhagia). An article written in the British Journal of General Practice seven years later notes that the Mirena is “probably underused in the UK at present” for treating heavy menstrual bleeding, and is not available at all GP practices.30

Side effects of the Mirena coil

Some women may experience side effects while using the Mirena coil. These include side effects experienced during and in the short term after insertion, and those experienced over a longer period of using the Mirena.

The below is a summary of side effects women may experience. Read a more in-depth breakdown of various Mirena coil side effects and how they are experienced.

Short-term side effects (during and after insertion) may include:

  • Pain, including during insertion and cramps following insertion
  • Infection — although if you test negative for infection prior to insertion, the risk of infection is negligible31
  • Fainting/cervical shock
  • Perforation of the uterus — this is when the Mirena makes a small hole in the wall of the uterus and is a rare occurrence. The chances of it happening are around 1 in 100032
  • Expulsion (where the Mirena coil falls out) — this is more likely to happen in the first three months following insertion. The risk of expulsion is 1 in 2033

Long-term side effects and risks of the Mirena coil include:

  • Hormonal side effects, including acne, breast tenderness, and headaches. There is no evidence to suggest that the Mirena causes weight gain or affects your libido34
  • Irregular bleeding and changes to periods. During the first 3-6 months of using a Mirena, you may experience changes to your period but this tends to improve over time35

Other risks and complications

Ectopic pregnancy

There is a small risk that you may become pregnant while using the Mirena coil, but if you do, there is an increased chance of an ectopic pregnancy. This is where the fertilised egg implants outside of the womb, as opposed to on the endometrium (lining of the womb). Usually, a fertilised egg in an ectopic pregnancy will implant in one of the Fallopian tubes (93-98%).36

An ectopic pregnancy is considered serious, and prompt diagnosis is essential in reducing the risk of complications. Unfortunately, it is not possible to save the pregnancy, and your doctor will advise on the most appropriate procedure to remove the egg. This might be through use of drug treatment (usually a drug called methotrexate) or through surgery.37

However, the Mirena actually reduces the overall risk of ectopic pregnancy when compared to using no contraception. The risk of ectopic pregnancy increases only if you become pregnant while using the Mirena coil, versus if you were to become pregnant without having a Mirena coil inside you.38

Abortion

It is safe to have an IUS inserted immediately after abortion, however the risk of expulsion appears to be higher.39 While the rate of expulsion is generally low, it has been found to be higher for second-trimester abortions than after first-trimester abortions.40

Ovarian cysts

Functional ovarian cysts are reported as a common side effect of LNG-IUS use, however, most are asymptomatic and resolve spontaneously.41

Should I get the Mirena coil?

It is important to weigh up the risks and benefits of any type of contraception you are considering using before making your choice. Because each woman is different, and there are many different factors that might affect the suitability of a particular method, it is essential to speak with your doctor about choosing the right contraception for you.

Your doctor may recommend a particular method but if there is a specific contraceptive you are interested in you can ask them directly if they think it would be appropriate. Against your medical history and lifestyle, they will help you understand the relative pros and cons of each.

Featured image Sarahmirk – Own work, CC BY-SA 4.0. Image is of a white person’s hand holding out the Mirena coil. The image has been repeated to create a ‘mirror’ effect, where both hands are facing the centre of the image. The hands are against a bright teal background

Page last updated January 2020
Next update due 2022

Dr. Diana Chiu, MBChB (Hons) MRCP PGCERT (Med Ed) PhD

Diana received her medical degree, with honours, from the University of Manchester. She then went on to receive basic and specialist medical training within the north west of England. She carried out in-depth research in medicine and was awarded a PhD in 2016. Currently, she is finishing her medical training at a large teaching hospital, and one of her greatest interests is medical education. She is an advanced life support instructor and writes regularly for post-graduate examination websites, and also holds a PGCERT in medical education with distinction.

View more

References

  1. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  2. Ibid
  3. NHS, Intrauterine system (IUS), NHS website, February 2018 https://www.nhs.uk/conditions/contraception/ius-intrauterine-system/ (accessed 6 December 2019)
  4. Ibid
  5. Stanczyk, F., ‘Structure — Function relationships, pharmacokinetics, and potency of orally and parenterally administered progestogens,’ in Lobo, R.A’s Treatment of the Postmenopausal Women (Third Edition), Elsevier Inc, 2007, p 779
  6. Jonsson, B., et al., ‘Effects of various IUDs on the composition of cervical mucus’, Contraception, vol. 43, no.5, 1991, pp. 447-458
  7. Guttinger, A., and Critchley, H.O., ‘Endometrial effects of intrauterine levonorgestrel’, Contraception, vol. 75, 2007, pp. S93–S98.
  8. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  9. Ibid
  10. The ESHRE Capri Workshop Group, Intrauterine devices and intrauterine systems, Human Reproduction Update, May/June 2008, vol 14, issue 3, pp 192-208
  11. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  12. Faculty of Sexual and Reproductive Healthcare (FSRH), UK Medical Eligibility Criteria For Contraceptive Use (UKMEC), 2016, [online], https://www.fsrh.org/ukmec/, (accessed 6 December 2019)
  13. NHS, Intrauterine system (IUS), NHS website, February 2018 https://www.nhs.uk/conditions/contraception/ius-intrauterine-system/ (accessed 6 December 2019)
  14. Faculty of Sexual and Reproductive Healthcare (FSRH), UK Medical Eligibility Criteria For Contraceptive Use (UKMEC), 2016, [online], https://www.fsrh.org/ukmec/, (accessed 6 December 2019)
  15. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  16. Ibid
  17. Ibid
  18. Ibid
  19. Ibid
  20. Verma, U., et al., Safe and cost-effective ultrasound guided removal of retained intrauterine device: our experience, Contraception Journal, July 2015, vol 92, issue 1, pp 77-80
  21. D. Asto, Ma. R., and E. Habana, Ma. E., Hysteroscopic-guided removal of retained intrauterine device: experience at an academic tertiary hospital, Gynecology and Minimally Invasive Therapy, April/June 2018, vol 7, issue 2, pp 56-60
  22. Royal College of Obstetrics and Gynaecology, Outpatient hysteroscopy, patient information, 19 December 2018, [online] https://www.rcog.org.uk/en/patients/patient-leaflets/outpatient-hysteroscopy/ (accessed 6 December 2019)
  23. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  24. NHS, Womb (uterus) cancer: causes, NHS website, 1 June 2018 [online] https://www.nhs.uk/conditions/womb-cancer/causes/ (accessed 6 December 2019)
  25. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  26. Ibid
  27. Kim, M.L., and Seong, S.J., Clinical applications of levonorgestrel-releasing intrauterine system to gynecologic diseases, Obstetrics and Gynecology Science, March 2013, vol 56, issue 2, pp 67-75
  28. NICE, Menorrhagia, Clinical Knowledge Summary, National Institute for Health and Care Excellence, December 2018, [online] https://cks.nice.org.uk/menorrhagia#!scenarioRecommendation (accessed 6 December 2019)
  29. Hurskainen, R., et al., Quality of life and cost-effectiveness of levonorgestrel-releasing intrauterine system versus hysterectomy for treatment of menorrhagia: a randomised trial, Lancet, January 2001, vol 357, issue 9252, pp 273-277
  30. Santer, Miriam, Heavy menstrual bleeding: delivering patient-centred care, British Journal of General Practice, March 2008, vol 58, issue 548, pp 151-152
  31. Walsh, T., et al., ‘Randomised controlled trial of prophylactic antibiotics before insertion of intrauterine devices. IUD Study Group’, Lancet, vol. 351, 1998,pp. 1005–1008
  32. Heinemann, K., et al., ‘Risk of uterine perforation with Levonorgestrel-releasing and copper intrauterine devices in the European Active Surveillance Study on Intrauterine Devices’, Contraception, vol. 91, 2015, pp. 274–297
  33. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  34. Ibid
  35. Ibid
  36. NICE, Ectopic pregnancy, Clinical Knowledge Summary, National Institute for Health and Care Excellence, May 2018, [online] https://cks.nice.org.uk/ectopic-pregnancy#!backgroundSub (accessed 6 December 2019)
  37. NICE, Scenario: suspected ectopic pregnancy, Clinical Knowledge Summary, National Institute for Health and Care Excellence, May 2018, [online] https://cks.nice.org.uk/ectopic-pregnancy#!scenario (accessed 6 December 2019)
  38. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)
  39. Ibid
  40. Grimes, D.A., et al., Immediate postabortal insertion of intrauterine devices, Cochrane Systematic Review, June 2010, [online], https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD001777.pub3/full (accessed 6 December 2019)
  41. FSRH Clinical Effectiveness Unit, ‘Intrauterine Contraception’, Clinical Guidance, April 2015, http://www.fsrh.org/standards-and-guidance/documents/ceuguidanceintrauterinecontraception/ (accessed 6 December 2019)