Uterine Fibroids

What are uterine fibroids? 

Uterine fibroids are growths arising from the muscle wall of the uterus. I

t is a round and firm structure amid the soft muscle layer. When cut open, the pale and dense cut surface gives us the impression that it is a growth of densely packed fibrous tissue. The growth attracts the common name of fibroid because of these characteristics.

In medical term, fibroid is known as leiomyoma. It reflects the true nature that the growth is a benign (not cancerous) tumour developed from abnormal muscle cells of the uterus, not fibrous tissue.

How common are uterine fibroids?

Uterine fibroids are the most common noncancerous growths in women. They can develop in women of any age after the onset of menstruation. The incidence increases with age. By 40 years old, more than 50 percent of women would have one or more fibroids. It is not uncommon to see mother and daughters or sisters in the same family with uterine fibroids.

What happens to uterine fibroids once developed?

Although the muscle cells made up of fibroids are abnormal in their genes, they are responsive to oestrogen, the female sex hormone.

During the years that a woman is menstruating, oestrogen stimulation leads to the continual growth of fibroids. In general, a fibroid increases in size by 1 cm a year.

During pregnancy, fibroids are known to grow more rapidly than during the non-pregnant period.

At menopause as oestrogen secretion ceases, many fibroids shrink in size slowly in the post-menopausal years. However, fibroids will not disappear completely, even years after menopause.

Some other growth factors are known to influence the growth of fibroids. These growth factors are not changed by menopause. This explains why some fibroids fail to shrink or may even continue to grow despite menopause.

Uterine fibroids can be classified according to their size (Table 1) or by their location in the uterus (Table 2):

Table 1: Classification of fibroids by size

Table 2: Classification by location

It is very common for fibroids of different sizes and locations to be present on the same uterus.

Does a uterine fibroid affect my fertility or my pregnancy?

A common condition, uterine fibroids are found in many women who experience difficulty in becoming pregnant. There is, however, no evidence to show that uterine fibroids cause infertility. If they do, it happens only in a very small proportion of women, for example, in a situation when a fibroid of moderate size located near the fallopian tube causes a blockade in the tube.

It is a common belief that uterine fibroid can cause the pregnancy to miscarry. Research has not shown a conclusive evidence for this belief. Why miscarriage seems to happen commonly in women who have fibroids can be explained by the facts that both fibroids and miscarriage are commoner as a woman becomes older. In fact, the great majority of women with fibroids, including those with a large fibroid, continue the pregnancy with no abnormal outcomes.

A peculiar complication of uterine fibroids during pregnancy is an uncommon change in the fibroid known as ‘red degeneration’. This condition causes abdominal pain that may require treatment with pain killers. This condition, however, has no adverse outcome on the pregnancy in terms of miscarriage or premature birth of the baby.