Understanding fibroids

What is a fibroid?

A fibroid is a non-cancerous (benign) growth of the muscle tissue in the womb (uterus). They can vary in size and can be small like a pea or large like a grapefruit. 

Do fibroids have any other names?

Fibroids can sometimes be called uterine myomas, fibromyomas or leiomyomas. These are all different medical words for describing fibroids.

How many women typically develop fibroids?

Fibroids are very common, and it is estimated that approximately 40% of women develop them.

What causes fibroids?

It is not clear why fibroids develop but they have been linked to oestrogen and progesterone exposure. There also appears to be a genetic predisposition for some women.

Are there different types of fibroids?

Fibroids can occur anywhere in the womb and are named according to where they grow:

1. Intramural fibroids: this means the fibroid is within the muscle wall itself. This is the most common type and can also be termed intramyometrial.
2. Subserous fibroids: these fibroids grow from the outside wall of the womb into the pelvis.
3. Submucous fibroids: these fibroids grow from the inside wall of the womb into the womb cavity.
4. Pedunculated fibroids: this type of fibroid is attached to the womb (uterus) by a narrow stalk.

Fibroids that are intramural or subserous in position are less likely to cause bleeding problems.

How are fibroids diagnosed?

Ultrasound is usually used to diagnose and assess fibroid size and position. If very large they can be sometimes felt through the skin by pressing on the lower abdomen or pelvis. 

What symptoms can fibroids cause?

For most women, fibroids do not cause any symptoms and they are found by chance, for example during an ultrasound scan or as part of an examination. When symptoms occur these might include:

• Bleeding problems: periods can become heavier or more painful. 
• Heavy periods can cause an iron deficient anaemia. Common symptoms of this include fatigue and pale skin. This can easily be tested for with a blood test.
• Tummy pain. 
• Bloating: if a fibroid is large this can cause swelling in the lower tummy.
• Pressure symptoms: rarely, if a fibroid is large, it might put pressure on the bladder or the bowel. If this happens urinary symptoms or a change in bowel habit can occur.
• Painful intercourse: if fibroids are close to the vagina this can cause discomfort during intercourse.  
• Depending on the size and position, fibroids can sometimes cause difficulties becoming pregnant or even infertility. Most women with fibroids will be able to get pregnant. 
• Problems can occur during pregnancy, but they are rare.

How are fibroids treated?

Monitoring:

If a fibroid is causing few or no symptoms it can be left alone. Sometimes repeat scans may be needed to assess for any fibroid growth.

Medications to improve symptoms: 

• Tranexamic acid. This can help to reduce heavy menstrual bleeding during your period. 
• Anti-inflammatory medications such as ibuprofen and mefenamic acid. These can help to reduce period pains and may lighten periods also.
• Sometimes contraceptive medications are prescribed to help reduce blood loss. One example is the Mirena coil. This is a plastic device that is inserted into the womb and releases a small amount of a progestogen hormone each day. It keeps the lining of the womb very thin meaning bleeding is lighter. It can also be used as the progestogen part of HRT for 5 years. However, it would not be suitable for women with fibroids that are distorting the cavity of the womb itself.
• A newer medication is called Ulipristal Acetate (Esmya). This medication can help shrink fibroids enabling the insertion of a Mirena coil.  
• Gonadotrophin-releasing hormone (GnRH) analogues. These medications lower total body oestrogen levels and are usually used for a short period of time only to reduce fibroid size before surgery.

Surgical treatments:

Not all women with fibroids will need surgery. Surgery is usually only recommended if fibroids are causing significant symptoms such as very heavy bleeding that has not got better with other treatments.

• Hysterectomy. This is the surgical removal of the womb (uterus).
• Myomectomy. In this operation, the fibroids are removed and the womb is left in place. This is preferable in women who may still want children. However, it is not always possible depending on the size, position and number of fibroids. 
• Uterine artery embolization. This involves inserting a thin flexible tube into a blood vessel that supplies the fibroid. Once there, a substance that blocks the artery is injected into the catheter. This means the fibroid loses its blood supply and shrinks.
• Myolysis. This means surgically shrinking the fibroid for example by endometrial ablation or ultrasound. 

Can fibroids turn into cancer?

It is very rare for a fibroid to become cancerous (around 1/1000).

What happens to fibroids after the menopause?

After the menopause fibroids usually shrink. MRI studies demonstrate that they can shrink by as much as 40%. This is thought to occur due to dropping levels of oestrogen and progesterone. 

However, the shrinkage of fibroids might be smaller if you take hormone replacement therapy (HRT) and, for a small number of women, use of HRT may be associated with an increase in volume of existing fibroids. HRT is not associated with the development of new fibroids. 

Despite this most women with fibroids can take HRT without any problems. This is because the level of hormone supplied by HRT is very low. Fibroids are therefore not a contraindication to HRT.  However, where there are concerns, it would be important to monitor for any fibroid-related symptoms and arrange regular follow-up for review.

You can read more about fibroids here: https://www.nhs.uk/conditions/fibroids/