Uterine fibroids are the most common noncancerous growths that can form in the uterus. They are sometimes called leiomyomas or myomas and can range in size from as small as a pea to as large as a grapefruit. Fibroids are discovered in up to 11% of pregnancies and are more often seen in people over 35 or of African ancestry.
While many individuals with fibroids experience no issues during pregnancy, understanding their potential impact can help patients and providers prepare for safe outcomes.
Can Fibroids Affect Pregnancy?
Most people with fibroids will go through pregnancy without complications. However, fibroids can be associated with an increased risk of:
- Fetal malpresentation (baby not in the head-down position)
- Preterm labor or preterm birth
- Placenta previa (placenta covering the cervix)
- Placental abruption (placenta separating too early from the uterus)
- Cesarean delivery
- Postpartum hemorrhage
In some cases, babies born to individuals with large fibroids may also have a lower birth weight.
Do Size and Location Matter?
The relationship between fibroids and pregnancy outcomes is still being studied. Some research shows that fibroids larger than 10 centimeters may increase the risk of complications. Interestingly, other studies suggest that the number or location of fibroids doesn’t significantly affect pregnancy outcomes.
Fibroid Changes During Pregnancy
Fibroids can grow or shrink due to hormonal and blood flow changes in pregnancy. About 60% of fibroids will change in size by more than 10%. Larger fibroids (greater than 5 cm) are more likely to grow, especially during the first trimester. In some cases, fibroids present early in pregnancy shrink or disappear by delivery.
Managing Fibroid-Related Pain
Up to 15% of patients with fibroids may experience pain during pregnancy.
- Mild to moderate pain: Often managed with acetaminophen.
- More severe pain: NSAIDs such as ibuprofen or indomethacin may be prescribed short-term before 32 weeks of pregnancy. These usually work within 48 hours. If pain persists, patients should contact their healthcare provider.
Pregnancy After Myomectomy
For patients who have had fibroids surgically removed (myomectomy), pregnancy requires careful monitoring. The major concern is uterine rupture, which depends on the size and location of prior incisions and the number of fibroids removed.
Healthcare providers will review surgical history and may recommend a detailed ultrasound in the second trimester to check the placenta’s position. Delivery planning—including timing and whether a cesarean is recommended—will be based on these factors.
