How Fibroids Affect Fertility and Pregnancy

Why Uterine Fibroids Sometimes Cause Pregnancy Complications

Doctor examining pregnant patient's belly

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Fibroids, also known as leiomyomas, are lumps of muscle tissue that grow in the wall of the uterus. 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 the uterus. They are usually benign, meaning 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. The location and size of the fibroids determine whether they need to be treated, as well as what type of treatment would be most effective.

Symptoms

Because fibroids are usually so small, they often go unnoticed. Fibroids are usually not dangerous, although they may affect quality of life. Many people experience no symptoms from their fibroids and may not even know they have them.

People 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 fade following menopause, due to decreased hormone levels.

Diagnosis

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

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

People at Risk 

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

Fibroids are most common in people in their 30s, 40s, and early 50s and in Black people, although people of all races can develop them. Having a family member with fibroids or being overweight or obese increases the risk of fibroids. 

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

Fibroids and Pregnancy Complications

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

  • Abnormal placenta
  • Bleeding early in the pregnancy
  • Breech presentation
  • Cesarean section (increased likelihood of delivery by C-section) 
  • Incomplete cervical dilation
  • Infertility, although fibroids are usually not considered the cause of fertility problems
  • Pain, most often in people 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. The exact mechanisms are not entirely understood but could include changes in the shape of the uterus and blockages of the cervix or fallopian tubes. Fibroids may shrink or "die out" in pregnancy as their blood flow is redirected to the fetus instead, but this is also not well understood.

Fibroids and Miscarriage

Most pregnancies with fibroids are normal and carried to term—and fibroids are no longer considered to increase the risk of pregnancy loss. In the past, in cases of miscarriage in pregnancies with fibroids, many doctors and pregnant women blamed the fibroids for causing the pregnancy loss. Some studies backed up this perceived increased risk, including a 2010 study that found the miscarriage rate for pregnancies with fibroids was 14% compared to 7.6% without fibroids.

However, more recent, large-scale studies have shown identical miscarriage rates for pregnancies with and without fibroids. One study with over 5,000 participants found that both groups experienced pregnancy loss at an incidence of 11%, suggesting that previous studies were poorly designed. Due to these results, researchers recommend that removing fibroids to prevent miscarriage is likely unnecessary.

Do Fibroids Need to Be Treated?

The approach to treatment may depend on 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. Recommended treatment depends on factors such as:

  • Desire to preserve the uterus
  • Future plans for pregnancy
  • Location of fibroids
  • 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. 

Medication

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:

  • Gonadotropin-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. 
  • Over-the-counter (OTC) pain medications: Medications such as ibuprofen and acetaminophen can help relieve symptoms of pain and discomfort. However, be sure to check with your doctor about which ones are safe for you to take if you are pregnant.
  • Other medications: There are other oral medications your doctor can prescribe that are used to treat uterine fibroids and heavy menstrual bleeding. Such medications can be helpful but are not a permanent or long-term solution.

People who are pregnant should not take nonsteroidal anti-inflammatory drugs (NSAIDs), which include ibuprofen, aspirin, and naproxen, after 20 weeks gestation due to the risks of serious side effects.

Surgery

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 (this is uncommon, occurring in only approximately 2.4% of cases), your doctor may discuss the possibility of removing them. However, as noted above, current research doesn't support removing fibroids to prevent miscarriage.

You should be aware, however, that it's unclear if removing fibroids will improve fertility or prevent pregnancy complications. However, some studies do show increased positive outcomes after these procedures.

This process, known as a myomectomy, involves surgically removing fibroids from the uterus. There are several different types of myomectomy that doctors may use and there are important risks to consider, including possible uterine rupture in pregnancy. There are other procedures, such as uterine artery embolization and radiofrequency ablation, which can destroy the fibroids without surgery. Fibroids are rarely removed during pregnancy unless there is a critical need to do so.

In more severe cases, or when pregnancy is no longer desired, a hysterectomy can be done to permanently cure the fibroids. 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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11 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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