The IUS is a small, T-shaped plastic frame. The stem of the 'T' contains a hormone called levonorgestrel. Levonorgestrel is similar to the natural hormone progesterone, which is produced by your ovaries.
The IUS helps to manage heavy periods and is an effective hormonal contraceptive. Over five years, fewer than one in 100 women who use the IUS will get pregnant. The IUS isn’t affected by other medicines and is safe to use if you’re breastfeeding. The IUS doesn’t protect you against sexually transmitted infections.
The type of IUS available in the UK is called Mirena. This can be placed in your womb for up to five years (or longer if you’re over 45). Your GP will only recommend the IUS to you if you're happy to have it in place for at least a year.
During each menstrual cycle, the lining of your womb (endometrium) thickens and gets ready for a fertilised egg to implant. If you don't become pregnant, your endometrium breaks down and you have a period. A period is your body's natural way of removing your endometrium. Heavy periods are sometimes caused by an overgrowth of your endometrium.
The IUS releases levonorgestrel very slowly into your womb. This hormone stops your endometrium from growing. This means your endometrium is thinner than usual so there is less to shed at the end of your monthly cycle and your periods are shorter and lighter.
The IUS works as a contraceptive by making it difficult for a fertilised egg to implant in your womb. It also thickens the mucus in your cervix (the neck of your womb), which makes it difficult for sperm to enter your womb. The IUS may stop your ovaries from producing eggs (ovulation) but this doesn’t happen in all women.
Your family and medical history will help determine whether or not the IUS is suitable for you. The IUS may not be suitable if you have had certain medical conditions, which include:
An IUS is usually fitted by your doctor or a specialist nurse. The procedure takes about 15 to 20 minutes.
Your doctor or nurse will place a speculum into your vagina to make it easier to see your cervix. He or she will then pass a thin tube, that contains the IUS, up through your vagina and into your womb. Your doctor or nurse will remove the tube once the IUS is in place. The IUS will open up into a T-shape when it's in your womb.
The IUS has two soft threads that will hang through your cervix into the top of your vagina. Your doctor or nurse will show you how to feel these threads to make sure the IUS is in place and hasn’t moved. It’s important to check the threads once a month.
You will usually have your IUS fitted within seven days of the start of your last period. This is when your endometrium is at its thinnest and your cervix most relaxed. This will make it easier to pass the IUS into your womb.
If you’re sexually active and the IUS is fitted a week or more after the start of your last period, you will need to use other forms of contraception for at least seven days.
You may notice that your periods become irregular and you have some bleeding between your periods (this is called spotting). You may also notice that your periods are heavier to start with. They should become lighter within three to six months. It's possible that they may stop completely.
During your period, it’s safe to use tampons. However, take special care when removing the tampon so that you don't pull the threads of the IUS.
Contact your GP if you feel unwell or have a high temperature, or have any smelly discharge from your vagina in the first three weeks after having an IUS fitted. If you have these symptoms, it’s possible you may have developed an infection.
You will need to have your IUS checked between three and six weeks after it’s inserted. Your doctor or nurse will check its position and ask if you’re having any problems.
Your doctor or nurse will explain how you can check the position of your IUS yourself by feeling the two threads in the top of your vagina but it’s important not to pull the threads. Check your IUS a few times in the first month and then regularly after each period.
Contact your GP or nurse if you:
The IUS may have moved out of place and you may need to have it re-fitted. If you think it has moved, use another contraceptive method until you've seen your GP or nurse.
If you need to have your IUS removed, your doctor or nurse will examine you and then remove the IUS by gently pulling on the threads. Don’t try to remove the IUS yourself.
You can usually have another IUS fitted immediately after having your old one removed.
The contraceptive effect of your IUS will disappear as soon as it's removed and your fertility will return to normal. If you don’t have a new IUS fitted immediately and don’t want to get pregnant, you will need to use alternative forms of contraception.
As with every procedure, there are some risks associated with having an IUS fitted. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your doctor or nurse to explain how these risks apply to you.
Side-effects are the unwanted but mostly temporary effects you may get after having the procedure.
You may feel faint while the IUS is being inserted, although this is unusual.
You may have some pain or discomfort, similar to period pains, after having your IUS fitted. If you need pain relief, you can take over-the-counter painkillers such as paracetamol or ibuprofen. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.
Other possible side-effects include light bleeding, breast tenderness, acne, headaches and mood changes. These side-effects should settle gradually over the next few months.
There is a small chance that your IUS can be expelled after it's inserted; over five years this happens to about one in 20 women.
Complications are when problems occur during or after the procedure.
It's possible that you may develop cysts on your ovaries. These are usually harmless and they usually get better without treatment.
There is a small risk of developing pelvic inflammatory disease. It’s also possible that the IUS could damage (perforate) your womb or cervix.
It’s possible that the threads may detach from the IUS. If you cannot feel the threads, use another form of contraception and contact your doctor. You may need an ultrasound scan to check the location of the IUS.
It's very unlikely that you will become pregnant after you have the IUS fitted. However, if you do, there is a small risk of having an ectopic pregnancy. An ectopic pregnancy is when a fertilised egg implants outside your womb, most often in one of your fallopian tubes. It's important to see your GP as soon as you think you may be pregnant to have your IUS removed. Your doctor will also check that it isn’t an ectopic pregnancy.
Yes, you may be able to have an IUS fitted.
An IUS can be fitted from four to six weeks after a vaginal or caesarean birth. You won’t be able to have an IUS fitted if you’re bleeding from your vagina and/or have pain. An IUS may not be suitable for you if you have: a history of fibroids; liver disease; breast, cervical or endometrial cancer; pelvic inflammatory disease; or bleeding from your vagina with no known cause.
You will need to use another method of contraception from three weeks after you give birth until you can have an IUS fitted.
Having an IUS won't affect your ability to breastfeed or your breast milk supply, and it’s safe to use while you’re breastfeeding.
If you aren't sure about whether an IUS would be suitable for you, speak to your GP.
Heavy periods (menorrhagia) are periods that interfere with your physical, emotional and social wellbeing, and stop you from doing your usual activities.
It's very difficult to measure the amount of blood lost during a period, but if your period is disrupting your usual activities, it’s possible that you may have heavy periods.
Signs to look out for include:
Heavy periods don't only disrupt your lifestyle but also put you at risk of developing anaemia. Around two in three women with heavy periods have iron-deficiency anaemia. This can make you feel tired and breathless and you may have palpitations – an unpleasant awareness of your heartbeat, often described as a thumping in your chest.
If you think your periods are unusually heavy, speak to your GP for advice.
It's very unlikely that you will become pregnant after you have an IUS fitted. However, if you do, your GP will advise you to have your IUS removed.
The IUS is an effective contraceptive. Over five years, fewer than one in 100 women who use the IUS will become pregnant.
If you do get pregnant with an IUS in place, there is a very small risk that you may have an ectopic pregnancy. An ectopic pregnancy is when a fertilised egg implants outside your womb, most often in one of your fallopian tubes. It's not possible for pregnancy to survive outside the womb and you may need immediate treatment.
If your pregnancy isn't ectopic, your GP will advise that you have your IUS removed immediately to reduce your risk of having a miscarriage or premature labour. However, removing the IUS also carries a risk of miscarriage so it’s important to discuss this fully with your doctor so you understand the risks. If you choose to leave the IUS in place and continue with your pregnancy, you will need to have regular check-ups throughout your pregnancy.
Your partner won’t be able to feel your IUS during sex but he might be able to feel the threads. However, this is unlikely.
If your IUS is in the correct position, your partner won’t be able to feel it. However, there are two thin threads that hang down into your vagina that he may feel during sex, although this is unlikely.
If you can feel the IUS or the threads, or your partner can feel them during sex, talk to your GP. Your doctor will check that the IUS hasn’t slipped into your cervix and may trim the threads to make them slightly shorter.