The hormonal coil, also known as an IUS (Intrauterine System), is a small plastic T-shaped device that is inserted into the uterus as a form of contraception.

The IUS releases a hormone called levonorgestrel into the womb which thickens the cervical mucus making it much harder for sperm to penetrate and reach into the uterus. In the case that the sperm manages to fertilise an egg, the hormone thins the lining of the uterus so that the egg is less likely to imbed itself into the uterine lining.

In some people, the IUS can even prevent ovulation (the release of an egg) and in these circumstances your periods can stop. This is not harmful to your body and your fertility will return to normal once the device is removed.

The hormonal coil cannot be used for emergency contraception, only the copper coil (IUD) can be used.

The hormonal coil is a soft plastic ‘T’ shaped device and contains a synthetic progesterone hormone called Levonorgesterol. It has two thin threads at the bottom that hang about 2cm down from your uterus, out of your cervix, and into your vagina. Your clinician will cut the threads to the right length for your body.

Your coil should not be visible as it sits within the uterus. It is, however, possible for your clinician to see your threads. This is completely normal and shows that your coil is still in place.

Here at Clarewell Clinics, we offer three types of the hormonal coil:

• Mirena – 6 year licence
• Kyleena – 5 year licence
• Jaydess – 3 year licence.

You will be able to discuss with your clinician in the consultation which coil will be suitable for you.

At the end of the licence period, the coil will need to be removed by a clinician or your health care provider. You will then be able to replace your coil or choose a different form of contraception, depending on your current contraceptive needs.

If you have a 52mg device fitted after the age of 45 years, this can remain in place until the age of 55, when we can safely assume you do not require contraception.

If a 52mg device is fitted for heavy menstrual bleeding only, then it can remain as long as it is managing your bleeding.

The copper coil and hormonal coil are similar in terms of their shape and size.

However, instead of releasing copper into the womb (like the IUD does), the IUS releases hormones that thickens the cervical mucus and thins the uterine lining, making it harder for an egg to fertilise and implant itself.

During perimenopause periods can become heavier, more frequent and more painful. Women who are going through menopause may consider the hormonal coil, more specifically – the Mirena coil, due to the role that it plays in hormone replacement therapy (HRT). The 52mg device can support perimensopausal women by stopping their periods altogether or making them less frequent.

The Mirena coil is the only IUS that is licensed for HRT.

The IUS is a method of long-acting reversible contraception (LARC). LARCs are extremely effective forms of contraception as there is no room for user error.

The IUS will begin to work immediately if it has been fitted within the first 5 days of your menstrual cycle. If it is fitted after the first 5 days have passed, you will need to use an extra form of contraception for 7 full days after fitting.

When inserted and placed correctly, the hormonal coil is over 99% effective. This means that fewer than 1 in 100 IUS users will become pregnant within 1 year. When the IUS is used for 5 years, fewer than 2 in 100 IUS users will become pregnant within 5 years.

Your coil should remain effective until it is removed. However, since progesterone is dispensed from the coil, the hormones will deplete towards the end of the licence period and you will not be protected from pregnancy after this period.

The coil will need to be removed or replaced after your licence period.

It is highly unlikely for the coil to fail (see the above question on effectiveness).

It may be that your IUS can move and sit lower in the uterus, however, it will still be effective and can remain in place as long as it is not causing any problems.

You may experience spotting, light bleeding and cramps for the first few days. However, this can last for up to 6 months before it settles.

Other side effects can include acne, breast tenderness, headaches, nausea, bloating and mood swings, which should calm down after the first few months. Please speak to your clinician if these side effects persist and are troublesome.

Initially, your periods may become erratic as the uterine lining thins. You may also experience longer and heavier menstrual bleeding, or just light occasional spotting within the first 6 months of use. This is normal and not a cause for concern.

You should be able to determine what your new cycle is going to be after a few months. 

It is possible for your periods to stop completely whilst using the IUS. This will return to normal when you choose to remove your IUS.

According to the Faculty of Sexual & Reproductive Healthcare, weight gain in those with an IUS is most likely to be a consequence of other factors, including an increase in age, and is not directly associated with the IUS itself.

Although the hormonal coil is more than 99% effective at preventing pregnancies while in use, it has no permanent effect on your future fertility.

Your fertility will return immediately after removal, meaning you could conceive straight away. If you are not planning to get pregnant, it is a good idea to start a new and effective method of contraception prior to your IUS removal.

There is a risk of pregnancy if there has been any penetrative sex in the 5 days before the coil is removed. 

There is little scientific evidence that the hormonal coil increases your breast size.

The hormones in the IUS can cause breast tenderness, due to water retention but this is not a definitive sign that your breasts are growing or have grown as a result of the IUS.

Acne is a well-known side effect of the hormonal coil due to the release of progesterone.

Progesterone stimulates androgen hormones, which can overstimulate the sebaceous glands. As a result, the skin becomes oily and the pores become clogged.

Like with all hormonal forms of contraception, it is possible for the IUS to affect your mood if you are sensitive to the hormone progesterone.

If you suffer with your mental health and are not sure if hormonal contraception is best suited to you, please discuss this with your clinician who will be happy to talk you through your options.

Using a hormonal coil may result in increased vaginal discharge. As a result of having a device in your uterus, you may notice a slight change in odour. If a STI test has been performed, the change in discharge is not usually a cause for concern unless it is offensive in odour.

Your IUS should not cause itching, redness, or other irritation around your vulva. Please contact your clinician if you are experiencing any of these changes.

There is not enough evidence to form a link between the IUS and cancer. However, due to the way that the Mirena coil works, it can affect your body differently if you have had certain cancers.

Manufacturers of the Mirena coil have suggested that you avoid using it if you have had:

• Cervical or womb cancer
• Liver cancer
• Hormone-dependant cancer (including breast cancer)
• Blood cancers

Please speak to your clinician before you decide whether or not to use the hormonal coil.

• It is easy to use and there is no room for user error once it has been fitted correctly.
• No one can tell that you are using contraception.
• It does not interfere with sex or daily activities.
• You can use a tampon or a menstrual cup with it.
• It can be inserted immediately after an abortion, a miscarriage, or childbirth and can be used while breastfeeding.
• The IUS does not affect your ability to get pregnant in the future. Your fertility returns almost immediately after removal (which is why we recommend avoiding unprotected sex for 7 days before removal).
• Your periods usually become much lighter, shorter and less painful. They may stop completely after the first year of use.
• The IUS can be used to manage heavy bleeding.
• The IUS does not contain oestrogen, so it is suitable for those who are unable to use contraception such as the combined pill, patch and vaginal ring.
• The IUS can also be used to protect the lining of your uterus if you are on HRT.

Movement is most common in the first few months after having the coil fitted. This is why it is important to check the strings of your coil more frequently in the first few months.

This is more likely to happen if:

• You have strong cramps during your period.
• You experience heavy bleeding with your period.
• Your IUS has not been inserted correctly.

SIgns that your hormonal coil may have moved are:

• You may not be able to feel the threads (although this can also be normal depending on if the threads have softened and wrapped around the entrance of the cervix).
• You can feel the plastic of the coil.
• You are experiencing cramping that is not cycle-related.
• You are experiencing bleeding in between periods, and unusual vaginal discharge.

Please let your clinician know if you suspect that your hormonal coil has moved.

It is highly unlikely for your coil to physically break, but there is a possibility that it may either move, or expel itself – which will cause it not to work.

If you think either of these are happening to you, please let your clinician know.

Serious complications from IUSs are rare. However, complications can arise during or soon after insertion, for example:

• The IUS may be pushed out of the uterus (expulsion), or move (displacement). The risk is higher in those with heavy menstrual bleeding, and those who have an IUS inserted immediately after childbirth. If the IUS comes out, it is no longer effective.
• The IUS can perforate the wall of the uterus during placement. If this happens, the IUS will need to be removed, sometimes through surgery. It is rare and occurs in only about 1 out of every 1,000 placements. If your clinician fitting the IUS is experienced, the risk of perforation is very low.
• Pelvic inflammatory disease (PID) after IUS insertion happens very rarely. Using an IUS does not by itself increase the risk of PID. Women with an undiagnosed STI at the time of IUS insertion are more likely to develop PID than women without an STI. We recommend screening for chlamydia and gonorrhoea before or during your IUS fitting where possible.
• Rarely, pregnancy may occur. If pregnancy occurs, and you wish to continue the pregnancy, the IUS needs to be removed. If the IUS remains in place during pregnancy, there are increased risks of miscarriage and infection.
• In the rare case that a pregnancy occurs with the IUS in place, there is a higher chance that it will be an ectopic pregnancy. This is a serious condition that needs medical attention right away.

The hormonal coil uses a form of the hormone progesterone, and is a good option for those who cannot use contraception that contains oestrogen. It may also be an option if you suffer with heavy and painful periods.

If you would like to discuss in more detail whether the hormonal coil is a good option for you, please book an appointment with one of our clinicians who will be happy to talk you through it.

We offer the hormonal coil to patients aged 18 and above. Patients who are under the age of 18 and are wanting to be fitted with the hormonal coil are able to do so on the NHS.

The hormonal coil is safe to use while breastfeeding and will not affect your milk supply.

Most antibiotics will not affect the effectiveness of your hormonal coil.