Fibroids and Fertility
Fibroids are benign (non-cancerous) smooth muscle growths of the uterus. Medical terms for fibroids are uterine leiomyomas and simply myomas. Fibroids are the most common growths found in young women. They grow from muscle cells in the uterus, can be found in the muscular wall and may protrude from the inside or outside surfaces of the uterus.
Fibroids are classified according to their location within the uterus. The uterus has three layers that are the inner lining (endometrium), the wall of the uterus which consists of smooth muscle (myometrium), and the outer lining (serosa).
Types of Fibroids
The diagram below demonstrates the different types/locations of fibroids within the uterus. A fibroid that grows in the muscular wall of the uterus is called an intramural (within the wall) fibroid. A fibroid that grows mainly on the outer surface of the uterus, under the serosa is called subserosal. A fibroid that grows just under the uterine lining inside the uterine cavity is called a submucous or intracavity fibroid.
Cause of Fibroids
Although the exact cause of fibroids is unknown, their growth may be related to a gene that controls cell growth. When this gene is functioning normally, cells grow normally. When the gene is functioning abnormally cells grow and divide at an accelerated rate. In this way, one cell becomes two, two become four etc. until finally a fibroid is detected. Fibroid growth is also affected by reproductive hormones such as oestrogen and progesterone, and certain growth factors. Abnormalities in the blood vessels around the uterus may also play a role in the development of fibroids.
Fibroid Risk Factors
Many factors are associated with the risk of developing fibroids, and these include;
- Women who have one or more pregnancies that develop beyond five months have a decreased risk of having fibroids.
- Use of birth control pills can generally protect against fibroids, but the use of the pill at an early age may increase the risk.
- Women who smoke appear to have a decreased risk of having fibroids. This may be due to an oestrogen lowering effect of smoking.
- Eating large amounts of red meat is associated with an increased risk of having fibroids, and eating green vegetables decrease the risk. Some studies have suggested that changes in diet may lead to changes in the incidence of symptoms associated with fibroids.
- Fibroids are 2-3 times more common in African American women, who tend to develop fibroids at a younger age, and have more numerous, larger and symptomatic fibroids.
- First degree relatives of women with fibroids have a 2.5 times greater risk of developing fibroids.
The majority of fibroids are small and do not cause any symptoms. However, some women have significant problems associated with fibroids that affect their quality of life including pelvic and abdominal pressure, pain and heavy periods.
Some women who have fibroids have abnormal periods that can be heavy and/or prolonged, and are often associated with pain. There are other possible causes of pain and heavy periods that may need to be excluded before assuming that such symptoms are due to fibroids.
Fibroids can range in size from being microscopic (tiny) to much larger. Larger fibroids may cause a feeling of pressure and fullness in the abdomen, similar to that of a pregnancy. If fibroids grow toward the back, pressure can cause pain in the lower back. Large fibroids can also be associated with discomfort with activity or intercourse, constipation and frequency of urination.
Fibroids and Fertility
Although fibroids are more common in women who experience problems with fertility, there is debate amongst fertility specialists about whether fibroids cause infertility and if fertility can be improved by treating fibroids. Theories about how fibroids may affect fertility include;
- The inside lining of the uterus may be enlarged or abnormally shaped.
- The fallopian tubes could be blocked (particularly at the point where they join the uterus).
- The anatomy of the fallopian tubes and ovaries may be altered making it more difficult for eggs to enter the fallopian tubes.
- Uterine blood flow may be abnormal.
- Fibroids protruding into the inner surface of the uterus may cause inflammation or release chemical substances, possibly making it more difficult for embryos to implant and/or increasing the risk of miscarriage.
Most fertility specialists believe that submucous fibroids decrease fertility, and that removing such fibroids may restore fertility. However, there continues to be debate as to whether intramural and subserosal fibroids affect fertility. Currently, there is no clear evidence that removing these latter types of fibroids improves fertility.
Large fibroids, especially those that protrude on the outside of the uterus may be felt during a routine pelvic examination. However, a pelvic examination can frequently miss if fibroids are present. An ultrasound examination performed by an experienced person can detect most fibroids. During fertility care a dye test such as a hysterosalipingogram or sonohysterogram is a good method of telling if fibroids are distorting the shape of the inner surface/lining of the uterus. Fibroids can be diagnosed during telescopic examinations called hysteroscopy and laparoscopy, which are often performed to find and/or treat certain causes of infertility. Please refer to our Bubtree fact sheets and web pages for more information on the above methods of diagnosing fibroids. Occasionally specialized x-ray examinations called an MRI or a CAT scan can be used to detect and assess fibroids.
Treatments for Fibroids
A surgical operation to remove fibroid(s) is called a myomectomy. There is much disagreement amongst fertility specialists about when a myomectomy should be performed in women who have fertility problems.
Most fertility specialists agree that fibroids that are within the uterine cavity or that cause significant distortion of the cavity (submucous fibroids) should be removed. Submucous fibroids can be removed by a telescopic procedure called a hysteroscopy. More information is available about hysteroscopy in our Bubtree fact sheet and web page.
However, what about a single small fibroid that is located within the muscular wall of the uterus but does not protrude into or distort the cavity? What if there were two such fibroids? What about a very large fibroid that is only attached to the outside of the uterus (subserous fibroid) by a thin stalk? This controversy exists because it is very difficult to do studies that prove a beneficial effect of myomectomy, and analysis of studies performed to date does not give a clear answer. Moreover, there are risks associated with performing a myomectomy.
If fibroids are large there may be a concern that they will grow in pregnancy, cause pain in pregnancy or rarely increase the risk of some pregnancy complications. Because of that, a fertility specialist may occasionally advise performing a myomectomy in preparation for pregnancy, even although surgery may not improve fertility.
Intramural and subserous fibroids can be removed by either an open operation called a laparotomy or by a telescopic procedure called a laparoscopy. The choice of which type of operation to perform will depend upon the number, size and location of fibroid(s), and the preference, training and the experience of the surgeon/fertility specialist performing surgery.
There may be significant complications associated with a myomectomy including heavy bleeding, blockage of one or both fallopian tubes, and scar tissue formation (adhesions). If the bleeding is very heavy then a blood transfusion may be required and very rarely it is necessary to perform a hysterectomy (remove the uterus) in order to stop the bleeding. Depending upon the details of such surgery a woman may be advised to have a caesarean section to deliver future babies and there is a small risk of the uterus rupturing in pregnancy due to a weakness in the wall of the uterus where surgery was performed. Given these risks and the uncertainty in many cases if fibroids are causing/contributing to fertility problems, the decision as to whether to perform a myomectomy is often complex and involves a detailed discussion with an experienced fertility specialist.
Uterine Artery Embolization
Fibroids can be treated by cutting off/blocking their blood supply by either surgery or inserting a plug (embolus) into the artery supplying them under x-ray control (uterine artery embolization). In a proportion of women who have fibroids embolization has been shown to be a viable alternative to surgery for managing associated symptoms such as heavy bleeding. A clear advantage of x-ray guided embolization is that surgery can be avoided in a proportion of women.
There have been a number of small studies that have assessed if embolization can be used to treat women who have both fibroids and infertility. A theoretical concern about embolization in women who wish to become pregnant is that if the blood supply to the uterus (womb) is reduced then this might have a negative impact on the pregnancy/baby. Whilst some small studies have suggested that there is no adverse affect of embolization on future pregnancies, other studies have found that embolization may be associated with a significant increase in the risk of miscarriage.
Risks associated with uterine artery embolization include failure to improve symptoms such as bleeding and pain (20-30%), readmission to hospital after the procedure with pain (10%), infection and unrecognized cancer.
To date there have been no large studies using appropriate scientific methods (randomization) comparing surgery for fibroids to embolization or comparing no treatment to embolization. Therefore, at the moment the role and safety of embolization in the management of fibroids and infertility is unclear.
Medication can occasionally be used to shrink fibroids. They are usually only given as a temporary measure, such as during the time a woman is preparing for surgery to remove fibroids. In some cases, medication can cause shrinkage of fibroids which may allow them to be removed through a smaller incision. Many women taking these medicines have a cessation of menstrual periods. The lack of periods can help women with anaemia from fibroid related heavy or prolonged menstrual bleeding to build their blood counts up before surgery, but in women who are anaemic other measures are often needed to improve their blood count such as iron treatment and/or a blood transfusion. Fibroids rapidly enlarge again after medication is discontinued. Since there are adverse effects associated with prolonged low estrogen levels, medication is only a temporary approach to managing fibroids.