Facts about Fibroids

FIBROID FACTS - I

. . . understanding how fibroids develop

The Fibroid Embolization Center
at the Northern Westchester Hospital, (888) 666-2002

What are Fibroids | Serosal Fibroids | Intra-Mural Fibroids | Sub-Mucous Fibroids

What are Fibroids of the Uterus?

They are benign growths, arising from the muscular wall of the uterus. Their origin is thought to be the muscle in the walls of uterine blood vessels.

Fibroids vary greatly in size, and can remain for years with little change. Others can grow much larger and reach the size of a 5 month pregnancy or more.

In pregnancy, pre-existing fibroids can increase 3-5 times in size. This is thought to be due in part to the very high estrogen level in pregnancy, as well as to other factors stimulating the pregnancy changes. Quite remarkably after pregnancy, these same fibroids can shrink to their pre-pregnancy size.

Menopausal patients who take estrogen show a varying response. Some who start with significant size fibroids may notice a slow increase in size, while others experience very little change at all.

Fibroids are extremely common. They are estimated to reach significant size in 25-30% of all Caucasians, and in 50% of women of African background. If very tiny fibroids are included, some studies suggest that by the menopause virtually every woman has them.

In most cases, there is more than one fibroid present. Sometimes there are many - 50 or more have been counted. A Solitary fibroid can occur, but is much less frequent.

Cancer in a fibroid is very uncommon (perhaps 1:750 to 1000). There is some data that suggests this cancer (called a sarcoma) may not arise from a pre-existing fibroid at all, but develop in an area of the uterus not a fibroid.

Fibroids are also called by other names such as: Myoma, Leiomyoma, Leiomyomata and Fibromyoma

The Symptoms and Effects that fibroids produce are very dependent upon the place in the uterus they develop.
There are three types of Fibroids: Serosal, Intra-Mural and Sub-Mucous. (They will be discussed in order with comments on how the location alters their effect.)

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Serosal Fibroids
(or those which develop in the outer portion of the uterus and expand giving the uterus a "knobby" appearance.)

A serosal fibroid develops below the capsule of the uterus, and slowly expands outwards. (Observe the animated drawing to the left.)

Probably because they are not trapped below the surface of the uterus, they can expand to large size.

They produce no change in menstrual flow, and no increase in the miscarriage rate. They are compatible with pregnancy (though because of their size they can become uncomfortable by causing increasing pressure).

Serosal fibroids produce a problem in pregnancy only if they are in the lower part of the uterus. There they can block the outlet of the pelvis making a C-Section the only way to deliver the baby.

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Intra-Mural Fibroids
(or those which develop within the wall of the uterus and expand making the uterus feel larger than normal during a pelvic exam.)

An Intra-mural fibroid develops below the capsule of the uterus, and slowly expands, increasing the bulk of the uterus. (Observe the animated drawing to the left.)

When there are many fibroids within the wall, the uterine cavity also expands. This can result in heavier menstrual flows.

Should the combined bulk of the fibroids (all types) be large enough to fill the pelvis tightly, a blockage of flow of urine from the kidneys may result. Though this is uncommon, it can damage the kidneys if left untreated. Hence once this blockage is discovered, these fibroids must be removed.

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Sub-Mucous Fibroids
(or those which are deep in the uterus and deform the cavity.)

A Sub-Mucous fibroid is one which expands into the cavity of the uterus. (Observe the animated drawing to the left.)

Although these are the least common fibroids (5%), they produce the most symptoms. Whereas periods with a huge serosal fibroid may cause no problems, even a tiny sub-mucous fibroid can cause gushing, heavy flows and prolonged periods.

Because fibroids have a poor blood supply, a pregnancy which implants on the fibroid itself (a random event) will generally end in miscarriage. But if the pregnancy implants well away from the fibroid - it may develop normally. There is also an injury to the lining of the uterus (extending well beyond the fibroid and called chronic endometritis) which may also a factor in pregnancy loss.