Fibroids are the most common growths in a woman’s reproductive system. Many women with fibroids have no symptoms at all, while others have symptoms ranging from heavy bleeding and pain to incontinence or infertility. These information pages explain what fibroids are, how they can affect your health and what your options are for treatment. For more information on heavy bleeding orhysterectomy, visit our pages on these topics.
What are fibroids?
Fibroids are tumours that grow in the uterus (womb). They are benign, which
means they are not cancerous, and are made up of muscle fibers. Fibroids can be
as small as a pea and can grow as large as a melon. It is estimated that 20-50%
of women have, or will have, fibroids at some time in their lives. They are rare
in women under the age of 20, most common in women in their 30s and 40s, and
tend to shrink after the menopause.
Although the exact cause of fibroids is unknown, they seem to be influenced
by oestrogen. This would explain why they appear during a woman’s middle years
(when oestrogen levels are high) and stop growing after the menopause (when
oestrogen levels drop).
According to US studies, fibroids occur up to nine times more often in black
women than in white women, and tend to appear earlier. The reason for this is
unclear. Also women who weigh over 70kg may be more likely to have fibroids.
This is thought to be due to higher levels of oestrogen in heavier women.
In the past, the contraceptive pill was thought to increase the risk of
fibroids, but that was when the pill contained higher levels of oestrogen than
it does today. Some studies suggest that the newer combined pill (oestrogen and
progestogen) and the mini pill (progestogen only) may actually help prevent or
slow the growth of fibroids.
Types of fibroids
Fibroids are categorised by where they grow in the uterus:
Intramural — these grow in the wall of the womb and are the
most common type of fibroid.
Subserous— these fibroids grow from the outer layer of the
womb wall and sometimes grow on stalks (called pedunculated fibroids). Subserous
fibroids can grow to be very large.
Submucous — submucous fibroids develop in the muscle
underneath the inner lining of the womb. They grow into the womb and can also
grow on stalks which, if long enough, can hang through the cervix.
Cervical — cervical fibroids grow in the wall of the cervix
(neck of the womb) and are difficult to remove without damaging the surrounding
If you have fibroids, you may have one or many. You may also have one type of
fibroid or a number of different types.
As the cause of fibroids is still unknown, there are no clear guidelines for
preventing them. However, there are some things you could do that may help
reduce your risk:
• Keep your weight in check. This will minimize estrogen
levels in your body.