What causes Uterine Fibroids?

Age

Uterine Fibroids become more common as women get older, until they reach the age where they go through the menopause. There seems to be a large increase in the number of fibroids diagnosed in women in their 40s. This does not necessarily mean that fibroids are more common in women in their 40s, but rather that existing fibroids could start to grow quicker or symptoms could become more obvious.

Number of children

Women who have given birth have a lower risk of developing Uterine Fibroids than those who have had no children. This risk becomes lower as a woman has more children and also if there are shorter gaps between each birth. Having children could lower the risk of fibroids because pregnancy limits the time a woman is exposed to high levels of a specific hormone called oestrogen.

High blood pressure or risk of heart disease

Women with high blood pressure or a risk of heart disease have a higher likelihood of developing fibroids. One study showed that high blood pressure is linked to a higher risk of developing fibroids, even when medical care and treatment with blood pressure medications was taken into account.

Menopause

Women who have gone through the menopause have a lower risk of developing Uterine Fibroids. Existing fibroids tend to shrink in postmenopausal women because oestrogen levels in the body are very low, and when deprived of oestrogen, fibroids shrink.

Ethnicity

Uterine Fibroids are 2-3 times more common in Afro-Caribbean origin women and tend to be larger, more numerous and develop at an earlier age.

Exercise

Women with active lifestyles who get plenty of exercise have a reduced risk of developing Uterine Fibroids. One study showed that the risk could be reduced by as much as 40%.

Family history

The development of Uterine Fibroids appears to be more common if there is a family history; women with fibroids are more likely to have a close female family member, such as a sister or mother, with the same condition compared to women without fibroids.

Obesity

There is a higher risk of Uterine Fibroids in overweight women and the risk seems to increase consistently the more overweight a woman is. This could be due to hormone changes associated with obesity.

Age of first period

The age of the first period varies greatly depending on regions, race, genetic factors, etc, but a rough average age is 13 years. There is a slightly higher risk of developing Uterine Fibroids if the first period happened at an early age. Women who were 10 years old or younger when they had their first period have a higher risk of Uterine Fibroids when compared with women who were 12 years old at the time of their first period. Women whose periods began at age 16 or older have a lower risk of developing Uterine Fibroids. The early onset of periods can slightly increase the risk of developing fibroids because the womb (uterus) wall (the myometrium) goes through more changes; called cell divisions, increasing the chance of an error being introduced into the process of cell divisions – which leads to fibroids forming.