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.
• Eat green vegetables and fruit, and avoid red meat. An
Italian study found that women who eat little meat but a lot of green vegetables
and fruit seem to be less likely to develop fibroids than women who eat a lot of
red meat and few vegetables.
• Some studies suggest the combined pill may protect against
fibroids by keeping hormone levels from peaking and falling. The pill comes with
its own set of side effects, however, so talk to your doctor about whether it’s
right for you.
It is estimated that 75% of women with fibroids do not have symptoms,
therefore many women don’t know they have fibroids. Whether or not you have
symptoms depends on the size of the fibroids and where they are in your womb.
This also affects the types of symptoms you are likely to have. For example, a
small fibroid in the wall of your womb probably won’t cause any problems,
whereas a large fibroid growing outward from your womb might press against your
bladder, causing bladder problems.
The most common symptom of fibroids is heavy menstrual bleeding. Other
symptoms include abdominal pain or pressure, changes in bladder and bowel
patterns and, in some cases, infertility.
Heavy menstrual bleeding (menorrhagia)
Heavy bleeding may involve flooding (a sudden gush of blood), long periods or
passing large clots of blood. Heavy bleeding is not always due to fibroids, but
when it is, it is usually associated with fibroids that grow into the womb
(submucous). Although it is unclear exactly why fibroids cause bleeding, it may
be that they stretch the lining of the womb, creating more lining to be shed
during a period.
Heavy bleeding can be distressing and can make every day activities
difficult. You will need to use extra sanitary protection and will probably need
to change towels or tampons frequently. Some women with heavy bleeding feel they
need to stay near a toilet during their periods. This can greatly restrict
activity and may be frustrating or tiring.
Anaemia (iron deficiency)
Some women with fibroids and heavy bleeding develop anaemia as a result of
blood loss. Anaemia can make you feel weak, dizzy and tired. If blood tests show
that you have anaemia, ask your doctor about supplements or changes in your diet
that might help. Foods such as liver, leafy green vegetables, dried fruit and
even red wine can help boost your iron levels.
Pain and pressure
Some women with fibroids experience painful periods, dull aches in their
thighs, back pain or constant pressure in the abdominal area that feels like
bloating or fullness.
Pain during your period may be due to large clots of blood pushing through
your cervix. Cramps could also be caused by the womb trying to force out a
submucous fibroid that is growing on a stalk in the cavity of the womb.
Large fibroids can make the womb big and bulky, which can lead to lower back
pain or pelvic discomfort. Some women with fibroids feel a dull ache in their
thighs or develop varicose veins in their legs. This happens when fibroids
become so large they press on nerves and blood vessels that extend to the
Occasionally, fibroids can cause sudden severe pain in the pelvic area or
lower back. This may be due to a fibroid on a stalk (pedunculated) that has
become twisted. This kinks the blood vessels in the stalk and cuts off the blood
supply to the fibroid. If you feel sudden severe pain and also have a fever or
feel sick, you should see your doctor. The fibroid may need to be removed or
your doctor may recommend bed rest and painkillers until the pain stops on its
Pain during sex
Fibroids that press on the cervix or hang through the cervix into the vagina
can make penetrative sex painful and can also cause bleeding during sex.