Uterine fibroids are common, affecting up to one in five women of child-bearing age. And though the thought of having one might send off alarm bells, the comforting truth is they’re usually harmless.

However, it’s possible for a fibroid to make it harder to conceive and having one can potentially increase the chance for complications once a woman is pregnant. Here’s what you should know about these growths, whether you’re trying for a baby or already have one on the way. 

What are uterine fibroids?

Uterine fibroids are knotty masses of muscle and fibrous tissue that grow in and around the wall of the uterus. Fibroids are nearly always benign tumors and are very common. In fact, they affect up to 20 percent of women of child-bearing age and up to 80 percent of women by age 50.  

Fibroids often go unnoticed, sometimes only getting picked up during a pelvic exam or prenatal ultrasound. But in some cases they can cause symptoms. These may include:

  • Heavy, long or painful periods
  • A full, heavy feeling in the lower abdomen
  • Abdominal bloating
  • Frequent urination
  • Painful sex
  • Lower back pain
  • Constipation

During pregnancy, the most common symptoms of fibroids are pain, vaginal bleeding and pelvic pressure, particularly in the second and third trimester.

Experts don’t know for sure what causes fibroids, though hormones (like estrogen and progesterone) and genetics are thought to play a role. They also seem to be more common in Black women. Other risk factors may include obesity, early menstruation onset and a diet that’s higher in red meat and lower in green vegetables.

Can you get pregnant if you have fibroids?

First, the good news: It’s rare for fibroids to cause fertility problems. Occasionally though, the growths can make it harder to get pregnant. Between 5 and 10 percent of women who seek help for infertility have fibroids, according to the American Society for Reproductive Medicine (ASRM). 

Depending on its size and location, it’s possible for a fibroid to cause a fallopian tube blockage or change the shape of a woman’s cervix or uterus, making it harder for sperm to reach and fertilize an egg. In some cases fibroids can also affect the ability of an embryo to successfully implant on the uterine wall.

If you have fibroids and are having trouble conceiving, both you and your partner should see a fertility specialist, the ASRM recommends. (It’s possible for fibroids to be the culprit, but the problem could also be caused by other factors related to you or your partner.) If the fibroid turns out to be the cause, it can be treated to improve your chances of getting pregnant. 

Can fibroids cause problems during pregnancy?

Fibroids aren’t typically problematic during pregnancy. And when they do cause symptoms, they’re usually minor — some abdominal pain, light vaginal bleeding or a feeling of pressure on the bladder.

Occasionally, estrogen may promote the growth of uterine fibroids. Since pregnant women churn out lots of the hormone — it helps the uterus (and your breasts) grow, maintains the uterine lining and increases blood flow — fibroids can sometimes grow during pregnancy. But the majority tend to shrink back down to their original size after giving birth. 

Fibroids do, ever-so-slightly, raise the risk of preterm delivery, and they can sometimes push the baby into an odd position for delivery or block off part of a baby's exit path through the cervix (which makes for a slightly higher chance of cesarean delivery). Both women who have fibroids and those who have had fibroids removed prior to becoming pregnant may be more likely to need a C-section as well, so you should let your practitioner know if that was the case for you.

While these increased risks can be unsettling to think about, they shouldn’t be a huge worry. Your provider will keep a close eye on the size and placement of your fibroid throughout your pregnancy, and the majority of these growths don’t affect your ability to have a healthy delivery and baby.  

How are fibroids treated during pregnancy?

Because fibroids aren’t usually problematic, they’re mostly treated conservatively during pregnancy and don’t require a specialist. Often symptoms like discomfort or occasional bleeding are managed with bed rest and hydration.

Nonsteroidal anti-inflammatory drugs (NSAIDs) or other pain medications may be prescribed, but they should be used for short periods under the supervision of your health care provider.

It’s possible for fibroids to be removed surgically during pregnancy. But since surgical procedures can pose risks to both a woman and her baby, they’re typically only performed in cases where the fibroid is very large or fast-growing. 

When to talk to a doctor about fibroids

Fibroids are usually benign and don’t always cause discomfort. That said, it’s still important to keep your doctor informed about your fibroid history and symptoms, since fibroids have the potential to affect your fertility and can cause possible pregnancy complications. Call your doctor if you’re experiencing vaginal bleeding, abdominal pain or pelvic pressure, whether you know it’s related to a fibroid or not.

If you’re pregnant and previously had a fibroid removed by another provider, let your current doctor know about it. That way, they can monitor you for possible (but unlikely) complications or risks.

Finally, see your doctor if you have a fibroid or a history of fibroids and are having trouble getting pregnant. Together you can determine if the fibroid is getting in the way of your ability to conceive, and if so, how to treat it.