Fibroids are benign (non-cancerous) growths of the muscle of the uterus (womb). They are sometimes called myomas, fibromyomas or leiomyomas, but most people call them fibroids. Fibroids are common – around 20% of women get them.

Fibroids are most common in women in their 40s and 50s, towards the end of the reproductive years. They are more common in women of Afro-Caribbean origin, who also tend to be affected at a younger age. Fibroids are more likely to be found in women who have had no children or who only have one child. Obesity (being very overweight) is also associated with an increased risk of developing fibroids. They do not appear to run in families.

Fibroids grow very slowly and tend not to cause any problems or symptoms in younger women. They can cause symptoms as they grow bigger, but even so, at least half of all fibroids cause no problems at all.

Fibroids can be tiny or very large and a woman may have one or many. Their growth is stimulated by the hormone oestrogen, which is released from the ovaries during the reproductive years. Fibroids tend to become smaller after the menopause when oestrogen levels fall.

There are different types of fibroids, named according to where they are found:-

  • Intramural fibroids are found within the muscular wall of the uterus.
  • Subserosal fibroids grow outwards from the outside wall of the uterus. They can become very large.
  • Submucosal fibroids grow from the inner wall of the uterus and can take up space inside the uterus. These account for only 5% of all fibroids.

The problems that fibroids may cause depend on their location. Fibroids are not the same as polyps. Polyps grow from the lining of the uterus (the endometrium) rather than from the underlying muscle (myometrium) as is the case with fibroids.

What are the symptoms?

Heavy periods

Up to half of all women with fibroids have heavy periods. In some cases this can lead to anemia. Fibroids do not usually cause other problems with the menstrual cycle, such as bleeding between periods.

Pressure symptoms

Fibroids tend to enlarge the uterus. This may lead to lower abdominal discomfort or backache, or may press on the bladder causing symptoms such as needing to pass urine more often than normal. The uterus may also press on the rectum causing constipation. Some women experience pain or discomfort during sexual intercourse (dyspareunia) because of fibroids.

Problems with fertility

It is estimated that fertility problems are one of the presenting features in about ¼ of women with fibroids. There is a well-established relationship between the presence of fibroids and lower fertility or childlessness. When compared to other causes of infertility, however, they are a relatively uncommon cause, being implicated in only 3% of couples. It may be that a delay in having children (whether voluntary or involuntary) predisposes to the development of fibroids and this is more often an association rather than a causative feature.

Fibroids can affect the shape and internal environment of the uterus. They can make it more difficult to conceive but they only account for about 3% of the total cases of infertility.


Fibroids can cause discomfort because of pressure symptoms. Heavier periods can lead to worse period pains. Severe pain is quite rare but can occur if a fibroid grows on a stalk, which they twists (torsion) or if a fibroid outgrows its blood supply causing it to break down (red degeneration).

Diagnosis of fibroids

A doctor may suspect fibroids if he or she feels an enlarged uterus during a pelvic examination (an “internal”). An ultrasound scan is a useful way of confirming the present of fibroids. Here, a probe is placed on the woman’s lower abdomen and sound save signals are translated into pictures on a screen.

Fibroids can be detected by chance when women have ultrasound scans during pregnancy. Fibroids can also be detected by hysteroscopy, where a small telescope is passed through the cervix to view the inside of the uterus, or by laparoscopy, where a camera is passed into the abdomen through a keyhole incision and the outer wall of the uterus can be seen.

Treatment of fibroids

Fibroids don’t need to be treated if they cause no symptoms, or only mild symptoms, and if the diagnosis is certain. A repeat ultrasound scan may be carried out to ensure that the fibroids are not growing too rapidly.


There are no long-term drug treatments that can “cure” fibroids. However, drugs are available that can help relieve the symptoms.

One group of drugs aimed at reducing the size of fibroids are called gonadotrophin releasing hormone analogues (GnRH analogues). These drugs stop the ovaries from producing hormones. Their effect is sometimes described as a “medical menopause” and they can cause menopausal symptoms such as hot flushes. However, there are increased risks of harmful side-effects such as osteoporosis (thinning of the bones) if they are given for more than six months. They may be used to control symptoms in women who are close to the menopause for whom symptoms may soon be about to improve anyway.

GnRH analogues are sometimes given before surgery on the uterus because shrinking the fibroids makes the operation easier.


  • Hysterectomy – this is a major operation to remove the uterus, usually via a “bikini-line” cut in the abdomen or, if the fibroids are not too large, via the vagina.
  • Myomectomy – this is the removal of individual fibroids, leaving the uterus intact. It is usually only considered for women who still wish to have a baby. This may be done with through small cuts in the belly, using a laparoscope (keyhole surgery), but may require an open operation.
  • Hysteroscopic resection – fibroids within the uterus can sometimes be removed during hysteroscopy using a hot wire loop (diathermy).
  • Uterine artery embolisation – this is a new technique in which the blood supply to a fibroid is blocked, causing the fibroid to shrink. It is still undergoing research and is not yet widely available.

Fibroids are often detected at a routine scan during pregnancy. They do not necessarily cause any problems. However, there is an increased risk of miscarriage, premature labor and bleeding in women who have fibroids so it’s important to consider seeking specialist care from an obstetrician.

Most fibroids (around 80%) do not increase in size during pregnancy despite the extra hormones. Fibroids sometimes cause a severe abdominal pain during pregnancy if they break down (this is called red degeneration). The treatment for this is rest and painkillers.

Cancer arising in a fibroid is very rare. However, surgery to remove fibroids may still be recommended if there are symptoms of pain, bleeding and/or rapid growth of fibroids, especially in a post-menopausal woman.