Fibroids, or uterine fibroids, are benign tumours that grow inside the uterus.
They form from the cells that make up the muscle of the uterine wall. Medically, they are known as leiomyoma or myoma of the uterus.
A fibroid can range in size, and can be as small as a pea or much, much larger – in some cases, the size of a football. They do not increase the risk of cancer and, in most cases, do not affect fertility.
However, it is not uncommon for fibroids to press against the fallopian tubes, or affect the implantation of a fertilized egg. They can also put pressure on areas such as the intestines and bladder.
Additionally, if a pregnant woman has a large fibroid blocking the opening of her uterus, she will need to have a caesarean section.
It is not certain what causes fibroids, but they are known to grow faster when a woman's oestrogen levels are high. This particularly applies to pregnant women, or women using the contraceptive pill.
They are normally discovered from around age 30 onwards, and tend to shrink once a woman reaches the menopause as her levels of oestrogen will also decrease. However, they can be surgically removed if deemed necessary.
Symptoms of fibroids include heavy, painful and prolonged periods; backache and pelvic pain; constipation; and the feeling of a full and heavy abdomen. However, it is also possible to bypass symptoms altogether, and some women are never aware that they have fibroids.