What are uterine fibroids?

Uterine fibroids are the most common form of non-cancerous (benign) tumours in women of reproductive age. They are also known as leiomyoma, leiomyomata, or myoma. They can grow anywhere in the womb and may cause different symptoms depending on their location. Fibroids are usually round or semi-round in shape and can range in size from a pea to a melon.

Female patient diagnosed with infertility


Around one in every three women with fibroids may experience symptoms which could interfere with daily life. Talk to your doctor if you experience these symptoms.

During your period, the body releases chemicals that cause the muscles in the uterus to contract. Muscle contractions can cause pain and lead to further contraction of the womb contributing to an increased level of pain.

Heavy periods can have an emotional and social impact and lead to iron-deficiency anaemia and tiredness.

If a period lasts longer than seven days, it may be deemed irregular. Additionally, if you have bleeding between cycles, this may also indicate fibroids.

Fibroids can cause pain or swelling in the pelvis.

You may have to go to the toilet more frequently if fibroids press on the bladder. Fibroids may press on the large intestine, causing constipation and pain during bowel movements.

Some women can experience pain during sex because the fibroids press on the cervix, which can have an impact on relationships.

Occasionally, fibroids can lead to problems with becoming pregnant or infertility (the inability to become pregnant).
Infertility can happen if fibroids are very large or submucosal, where they grow into the cavity of the womb. Depending on their type and size, fibroids can sometimes prevent a fertilised egg from attaching itself to the lining of the womb, or they may block the fallopian tube, making pregnancy difficult.
In some cases, fibroids may also lead to complications during pregnancy for both the mother and child, increasing the risk of miscarriage and can cause problems during labour.


Fibroids have different names and descriptions based on their location within the womb (uterus).

  • Intramural fibroids: within the muscle wall of the womb
  • Pedunculated fibroids: attached by a stalk to the outside or inner wall of the womb
  • Submucosal fibroids: inner wall into the womb
  • Subserosal fibroids: outside wall of the womb into the pelvis


There are many risk factors associated with fibroids and hormonal changes can promote their occurrence:

Fibroids are more prevalent in peri-menopausal women (approaching menopause). However, they can occur in women of reproductive age.

If members of your family have had fibroids, you may be at higher risk of developing the same condition.

Fibroids are thought to occur more often in women of African-Caribbean origin.

Women who started their period when 10 years old or younger have a higher risk of fibroids when compared with women who were 12 years or older at the time of their first period.


Women who have given birth have a lower risk of developing fibroids. This may be because pregnancy limits exposure to high levels of oestrogen.

Menopause limits oestrogen and progesterone levels and therefore women who have gone through the menopause have a lower risk of developing fibroids.

There is a higher risk of fibroids in overweight women. This is likely due to hormone interactions associated with obesity.

Women who exercise regularly may have a reduced risk of developing fibroids.

Women with high blood pressure have a higher likelihood of developing fibroids due to additional pressure on the cardiovascular system.