What are the complications of uterine fibroids?

EFFECT ON FERTILITY

Large fibroids may cause infertility in the following way:

• By impairing the uterine lining.
  
• By blocking the fallopian tubes.
  
• By distorting the shape of the uterine cavity.
  
• By altering the position of the cervix and preventing sperm from reaching the uterus.

Some evidence suggests that even small fibroids may reduce the chances of pregnancy in women who are undergoing assisted reproductive techniques. Treatments to reduce fibroids may be helpful in such women, although there has been little research on this subject.

EFFECT ON PREGNANCY

Fibroids pose some risk to a pregnancy:

• A cesarean section may be required in cases where multiple fibroids, particularly those located in the lower part of the uterus, block the vagina during pregnancy. Fortunately, this is a rare occurrence.
  
• Multiple fibroids can also increase the risk for miscarriage. In one 2001 study the presence of intramural fibroids halved the chances for a successful pregnancy. (The largest fibroid observed in the study was less than an inch.)
  
• Fibroids can degenerate during pregnancy causing pain and may cause premature labor.

ANEMIA

Anemia from iron deficiency can develop if fibroids cause excessively heavy bleeding.

Most cases of anemia are mild, but even mild anemia can cause weakness and fatigue. Moderate to severe anemia can also cause shortness of breath, rapid heart rate, lightheadedness, headaches, ringing in the ears (tinnitus), irritability, pale skin, restless legs syndrome, and mental confusion. Heart problems can occur in prolonged and severe anemia that is not treated.

URINARY TRACT INFECTION

Large fibroids that press against the bladder occasionally result in urinary tract infections. Pressure on the ureters may cause urinary obstruction and kidney damage.

SEVERE PAIN

Fibroids can cause cramping during a period, which can be quite intense at times.

Pain can also develop if the blood supply is cut off from the fibroid tissue. In such cases, the cells blacken and die (called necrosis) from lack of oxygen. This event may occur under the following circumstances:

• A very large fibroid outgrows its own blood supply.
  
• A pedunculated fibroid (one that grows on a stem from the uterine wall) becomes twisted, thus cutting off its blood supply.
  
• Pregnancy occurs, in which the risk for fibroid cell degeneration and necrosis increases.

LEIOMYOMAS THAT SPREAD OUTSIDE THE UTERUS

Rarely, a fibroid breaks away from the uterus and develops in other locations.

They are typically one of the following:

• Benign Metastasizing Leiomyoma or BML (which usually spreads to the lung).
  
• Disseminated Peritoneal Leiomyomatosis (which spreads to the abdominal wall).

Neither is cancerous, although there is some evidence that BML, which often occurs after menopause, may represent a slow-growing variant of leiomyosarcoma.

UTERINE CANCER

Fibroids are nearly always benign and noncancerous, even if they have abnormal cell shapes.
Cancer of the uterus nearly always develops in the lining of the uterus (endometrial cancer).
Only in rare cases (a less than 0.1% incidence) does cancer develop from a malignant change in a fibroid (called leiomyosarcoma).
Nevertheless, rapidly enlarging fibroids in a premenopausal woman or even slowly enlarging fibroids in a postmenopausal woman require surgical evaluation to rule out cancer.