What are fibroids?

Fibroids, also known as uterine leiomyomas or fibromyomas, are benign (non-cancerous) tumours that grow in and around your uterus. Made up of muscle and fibrous tissue, they can vary in size from being invisible to the naked eye to filling the entire abdomen.

The size of a fibroid is referred to in relation to the size of the foetus; a 10-week sized fibroid, for example, is the same size as a foetus that is 10 weeks old.

What are the causes of fibroids?

The exact cause of fibroids is unknown, although research points to the over-production of oestrogen as being the most likely factor. This is because in most cases, they increase in size when oestrogen levels are highest, such as during pregnancy, and decrease when they are low, such as after the menopause.

Genetics may also play a part; if a close family member has them, you’re more likely to develop them.

Fibroids: the main types

Fibroids can develop in or around the uterus, and are classified according to their location in the body:

• Intramural fibroids: the most common type, these arise in the muscles that form the wall of the uterus.
• Subserosal fibroids: these grow outside the uterus wall into the pelvic area. Since they are not restricted by the size of the uterus, they can become very large in size.
• Submucosal fibroids: these develop in the muscle just under the inner lining of the uterus. As they expand, they can grow into the centre of the uterus, the space that would be occupied by the growing foetus if you were pregnant.
• Pedunculated fibroids: these grow outside of the uterus, joined to the outer muscle layer via a fibrous stalk.
• Cervical fibroids: these form in the cervix, which is at the entrance to the uterus.

What are the symptoms and complications of fibroids?

The most common fibroid symptoms are heavy, prolonged or painful periods and a feeling of pressure in your lower abdomen. Other symptoms include:

• Bleeding between periods
• Abdominal swelling or bloating
• Feeling pressure in the lower part of your abdomen
• Frequent urination
• Lower back pain
• Constipation, as fibroids can sometimes press against the rectum
• Haemorrhoids
• Pain during sex
• Miscarriage
• Difficulty falling pregnant
• Premature labour

How are fibroids diagnosed?

Fibroids are most often found during a routine pelvic examination. In addition to a complete medical history and physical and pelvic and/or abdominal examination, diagnostic procedures for fibroids may include:

• X-ray - electromagnetic energy used to produce images of bones and internal organs onto film.
• Transvaginal ultrasound - an ultrasound test using a small instrument, called a transducer, that is placed in the vagina.
• Magnetic resonance imaging (MRI) - a non-invasive procedure that produces a two-dimensional view of an internal organ or structure.
• Hysteroscopy - visual examination of the canal of the cervix and the interior of the uterus using a viewing tube (hysteroscope) inserted through the vagina.
• Endometrial biopsy - a procedure in which a sample of tissue is obtained through a tube which is inserted into the uterus.
• Blood test (to check for iron-deficiency anemia if heavy bleeding is caused by the fibroid.)