What are fibroids?

A fibroid is a benign (non-cancerous) growth of the womb (uterus). They are also called uterine myomas, fibromyomas or leiomyomas. Their size can vary. Some are the same size as a pea and some can be as big as a melon. Fibroids can increase in size, decrease in size or even go away with time. They can occur anywhere in the womb and are named according to where they grow:

  • Intramural fibroids grow within the muscle tissue of the womb. This is the most common place for fibroids to form.
  • Subserous fibroids grow from the outside wall of the womb into the pelvis.
  • Submucous fibroids grow from the inner wall into the middle of the womb.
  • Pedunculated fibroids grow from the outside wall of the womb and are attached to it by a narrow stalk.

How common are fibroids?

They are common. At least 1 in 4 women develops one or more fibroids in her lifetime. They usually develop in women aged 30-50 and can sometimes run in families. It is common to have several of various sizes, although some women just have one. Fibroids are more common in women from Afro-Caribbean origin. They also tend to be larger, occur at an earlier age and are more likely to cause symptoms in Afro-Caribbean women.

Fibroids are also more common in women who weigh over 70 kg (11 stones). This is thought to be due to the higher levels of oestrogen hormone that occur in larger women – see ‘What causes fibroids?’, below.

What causes fibroids?

A fibroid is like an overgrowth of smooth muscle cells. (The womb is mainly made of smooth muscle.) It is not clear why they develop. Fibroids are sensitive to oestrogen, the hormone that is made in the ovary. Fibroids tend to swell when levels of oestrogen are high – for example, during pregnancy. They also shrink when oestrogen levels are low – after the menopause. This shrinkage of the fibroids after the menopause may be delayed if you take hormone replacement therapy (HRT).

What symptoms and problems are caused by fibroids?

Symptoms only occur in about 1 in 3 women with fibroids. Many women who have fibroids are not aware that they have them. Sometimes one is found during a routine examination by a doctor or by chance during a scan which you may have for another reason. Symptoms may include:

Heavy or more painful periods

Fibroids do not disturb the menstrual cycle but bleeding is often heavier than usual, sometimes with more pain. This can lead to low iron levels and to anaemia which will be diagnosed by a blood test. This is easily treated with iron tablets.

Bloating or swelling

If a fibroid is large you may have discomfort or swelling in the lower abdomen. Some women experience lower back pain due to their fibroids.

Bladder or bowel symptoms

Occasionally a fibroid may press on the bladder which lies in front of the womb. You may then pass urine more often than usual. Rarely, pressure on the bowel (which lies behind the womb) may cause constipation.

Pain during sexual intercourse

If the fibroids grow near to the vagina or cervix (neck of the womb) then this can cause pain or discomfort during sexual intercourse. This is called dyspareunia.

Miscarriage or infertility

If the fibroids grow into the cavity of the womb they can sometimes block the Fallopian tubes. This can cause problems conceiving, although this is not common. Very rarely, fibroids can be a cause of repeated miscarriages.

Problems during pregnancy

Having one or more fibroids does not cause any problems in the vast majority of women when they are pregnant. Occasionally, you may have pain from your fibroid. This may be caused by the fibroid growing too large for its blood supply or twisting, if the fibroid has a stalk (also called pedunculated).

However, fibroids can be associated with an increased risk of having a Caesarean section, the baby lying breech (rather than head first) and early labour. Your doctor will advise you further if you are pregnant and have fibroids.

How are fibroids diagnosed?

Some fibroids can be felt during an internal (vaginal) examination by a doctor. Sometimes an ultrasound scan or other tests are done to confirm the diagnosis and to rule out other causes of any symptoms.

What are the treatment options for fibroids?


If your fibroids are not causing any symptoms then treatment is not usually needed. Many women choose not to have treatment if they have symptoms that are not too bad. After the menopause, fibroids often shrink and symptoms tend to go or ease. You can change your mind and consider treatment if symptoms get worse. Your doctor may advise you to have a repeat scan to assess the growth and size of your fibroids.

Medication to improve symptoms

The following medicines are used to treat heavy periods whatever the cause, including heavy periods that are caused by fibroids. These medicines may not work so well if your fibroids are large. However, one or more of the following may be worth a try if your periods are heavy and the fibroids are small:

  • Tranexamic acid is taken 3-4 times a day, for the duration of each period. It works by reducing the breakdown of blood clots in the womb.
  • Anti-inflammatory medicines such as ibuprofen and mefenamic acid. These also help to ease period pain. They are taken for a few days at the time of your period. They work by reducing the high level of a chemical (prostaglandin) in the lining of the womb. Prostaglandin seems to contribute to heavy and painful periods.
  • The contraceptive pill may help you to have lighter periods and can often help with period pain too.
  • Levonorgestrel intrauterine system (LNG-IUS) is similar to the coil that is used for contraception. It is inserted into the womb and slowly releases a regular small amount of progestogen hormone called levonorgestrel. It works by making the lining of the womb very thin, so bleeding is lighter. However it can sometimes be difficult to insert into the womb in women with fibroids.

Medication to shrink the fibroids

Some women are given a gonadotrophin-releasing hormone (GnRH) analogue. This is a hormone medicine that causes you to have a very low level of oestrogen in your body. Fibroids shrink if the level of oestrogen falls. This can ease heavy periods and pressure symptoms due to fibroids. However, a low oestrogen level can cause symptoms similar to going through the menopause (hot flushes, etc). It may also increase the risk of osteoporosis. Therefore this treatment is given for a maximum of six months.

GnRH analogues, such as goserelin (eg Zoladex®) or leuprorelin acetate (eg Prostap® SR), are often prescribed for three to four months before having an operation, which will make it easier to remove fibroids. Sometimes a low dose of HRT is also given to reduce the incidence of menopausal side-effects.

A new medication treatment undergoing trials

A medicine called ulipristal acetate (UPA) has shown promise in preliminary research trials. This is currently used as an emergency contraceptive. It works by blocking the effects of the hormone progestogen. Progestogen is thought to play a role in fibroid development and so it was thought that this medicine may help to shrink fibroids. A small research trial has concluded that it does seem to have an effect on shrinking fibroids, with side-effects not being too troublesome. Further larger clinical trials are needed to establish whether this is indeed a good treatment option.

Surgery and other operative treatments

There are several different operations available to remove and treat fibroids.

This is the traditional and most common treatment for fibroids which cause symptoms. Hysterectomy is the removal of the womb. This can be done by making a bikini scar in the lower abdomen. Or, if the fibroids are small enough, the womb can be removed through the vagina so there are no scars. A hysterectomy may be a good option for women who have completed their family. See separate leaflet called ‘Hysterectomy’ for more detail.

This is a possible alternative, especially in women who may wish to have children in the future. In this operation, the fibroids are removed and the womb is left. This procedure is not always possible. This operation can be done through an incision (cut) in the abdomen, via keyhole surgery (laparoscopically) or through the vagina (hysteroscopically). The type of operation depends on the size, number and position of the fibroids. Recurrence of the fibroid is fairly common after a myomectomy. There is a risk of very heavy bleeding with this operation. Your surgeon should advise you that a hysterectomy may be needed if that situation arose.

Endometrial ablation
This procedure involves removing the lining of the womb. This can be done by different methods. For example, using laser energy, a heated wire loop or by microwave heating. This method is usually only recommended for fibroids close to the inner lining of the womb.

MRI-guided focused ultrasound
This treatment sends pulses of high power ultrasound through the skin of the lower abdomen. It is targeted at the fibroid, using the MRI scanner. It is effective but there is no research yet on the long-term outcome for women trying to conceive.

Uterine artery embolisation
This procedure is done by a specially trained radiologist (X-ray doctor) rather than a surgeon. It involves putting a catheter (a thin flexible tube) into an artery (blood vessel) in the leg. It is guided, using X-ray pictures, to an artery in the womb that supplies the fibroid. Once there, a substance that blocks the artery is injected through the catheter. As the artery supplying the fibroid becomes blocked it means the fibroid loses its blood supply and so the fibroid shrinks. The complete process of fibroid shrinkage takes about 6-9 months but most women notice a marked improvement in their symptoms within three months. There is a good chance of success with this procedure but it does not work in every case.

Other techniques
MRI-guided laser ablation is a newer technique. In this procedure a small needle is put through the skin into the centre of the fibroid. The correct position of the needle is shown by the MRI scan. The laser energy is then passed down the needle, which destroys the fibroid. This technique is not suitable for all types of fibroid. There is not enough evidence currently to justify using this technique routinely.

Further information

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