How Fibroids Affect Fertility and Pregnancy

Why Uterine Fibroids Sometimes Cause Pregnancy Complications

Doctor examining pregnant patient's belly

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In This Article

Fibroids, also known as leiomyomas, are lumps of muscle tissue that grows in the wall of the uterus in many women. While these growths are common, they can sometimes cause pregnancy complications such as pain, infertility, miscarriage, or preterm labor

What Are Fibroids?

Fibroids are muscular tumors that may develop in the wall of a woman's womb. They are usually benign, meaning they are not cancerous. Fewer than 1 in 1,000 fibroids are cancerous.

Fibroids fall into one of four categories based on the location of the growth:

  • Intramural: In the wall of the uterus
  • Subserosal: On the outside of the uterus
  • Submucosal: In the uterine cavity
  • Pedunculated: Outside the uterus attached by a stem

Fibroids range from small (seed-sized) to large (grapefruit-sized). Women who develop them may have one or several of the tumors. The location and size of the fibroids determines whether they need to be treated as well as what type of treatment would be most effective.


Because fibroids are usually so small, they often go unnoticed. Fibroids are usually not dangerous to a woman's health, although they may affect her quality of life. Some women experience no symptoms from their fibroids and may not even know they have them.

Women who do have symptoms may experience: 

  • Anemia
  • An enlarged lower abdomen and a feeling of fullness
  • Bleeding between periods
  • Chronic vaginal discharge
  • Constipation or other digestive issues
  • Difficulty urinating
  • Long periods, heavy menstrual bleeding, and/or menstrual pain
  • Lower back pain
  • Painful sex
  • Pressure on the bladder, causing frequent urination 
  • Pressure on the rectum, causing constipation or difficult bowel movements

Such symptoms often begin to decline following menopause due to decreased hormone levels.


Fibroids are typically discovered during a pelvic exam or when a woman is receiving prenatal care. A doctor may confirm a diagnosis using tools such as: 

  • Computed tomography (CT)
  • Laparoscopy
  • Hysterosalpingography (HSG)
  • Magnetic resonance imaging (MRI)
  • Ultrasound

Women at Risk 

Fibroids are very common. By age 35, 40 to 60% of women have them. By age 50, the incidence jumps to 70 to 80%. 

Fibroids are most common in women in their 30s, 40s, and early 50s and in African American women, although women of all races can develop them. Having a family member with fibroids or being overweight or obese also puts women at greater risk of fibroids. 

Why some women develop fibroids and others don't is unknown. Genetics and hormones appear to play a role. 

Fibroids and Pregnancy Complications

Usually, women with fibroids have normal pregnancies. However, in some women (10 to 30%), fibroids cause complications with pregnancy or labor. These problems can include: 

  • Abnormal placenta
  • Bleeding early in the pregnancy
  • Breech presentation
  • C-section - women with fibroids are much more likely to need to deliver by cesarean section 
  • Incomplete cervical dilation
  • Infertility, although fibroids are usually not the cause of fertility problems
  • Miscarriage
  • Pain, most often in women with fibroids that are larger than 5 centimeters during the second and third trimesters 
  • Placental abruption (separation of the placenta from the uterus 
  • Postpartum hemorrhage
  • Preterm delivery
  • Slow labor

In about a third of women, fibroids grow during the first trimester of pregnancy. Fibroids can sometimes prevent pregnancy, although this tends to be uncommon and the exact mechanisms are not entirely understood. 

The Link Between Fibroids and Miscarriage

Although most pregnancies with fibroids are normal, the tumors can cause miscarriages, especially early in pregnancy. The miscarriage rate for women with fibroids is 14% vs 7.6% for women who do not have fibroids. 

The risk of a miscarriage appears to increase with multiple fibroids. How fibroids cause miscarriage is unknown. One factor may be that the tumors restrict blood supply to the developing placenta and fetus. 

Do Fibroids Need to Be Treated?

The approach to treatment may depend on your symptoms as well as the size and location of the fibroids. If you don't have symptoms, your doctor may just keep an eye on the size of your fibroids.

The treatment that is recommended depends on factors such as:

  • Desire to preserve the uterus
  • Location of fibroids
  • Future plans for pregnancy
  • Number of fibroids
  • Size of fibroids
  • Symptoms you are experiencing

Your future fertility plans are a major factor in the course of treatment. If you are planning to become pregnant in the future, there are some treatment options that should be avoided. 


Pain and heavy menstrual bleeding from fibroids can be treated with the use of medications. Some of the options that your doctor may recommend include:

  • Gonadotropic-releasing hormone (GnRH) agonists: These medications, usually administered by injection or nasal spray, can be used to temporarily shrink fibroids. However, the fibroids usually return once you discontinue use.
  • Hormonal birth control: Birth control pills or a progestin-releasing intrauterine device (IUD) can often help alleviate the symptoms of fibroids.
  • Iron supplements: If you're anemic from heavy bleeding, your doctor may recommend iron pills to restore your levels of this nutrient. 
  • Oral therapy medications: There are also medications your doctor can prescribe that are used to treat uterine fibroids and heavy menstrual bleeding. Such medications can be helpful, but may not be a permanent or long-term solution.
  • Over-the-counter (OTC) pain medications: Medications such as ibuprofen and acetaminophen can help relieve symptoms of pain and discomfort.


Sometimes surgery (or other methods of shrinking or destroying the tumors) is recommended for fibroids that are causing moderate to severe symptoms or pregnancy complications. For example, if it's suspected that your fibroids are contributing to fertility problems or recurrent miscarriages, you can talk to your doctor about removing them.

You should be aware, however, that it's unclear if removing fibroids helps improve fertility or prevent miscarriages.

Fibroids are rarely removed during pregnancy unless there is a critical need to do so. This process, known as a myomectomy, involves surgically removing fibroids from the uterus. There are several different types of myomectomy that doctors may use.

The only cure for fibroids is to perform a hysterectomy. This is a surgery that involves the complete removal of the uterus. By removing the uterus, the fibroids are unable to grow back.

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