The impact of fibroids on pregnancy depends on their size, number, and location within the uterus.
Pregnant women with uterine fibroids may experience the following:
- Lower abdominal pain: This is the most common complication. The larger the fibroid, the more likely it is to cause pain, especially during the second and third trimesters.
- Miscarriages: These occur mainly in the first trimester and are associated with the number and location of the fibroids. In practical terms, a single fibroid carries a lower risk compared to multiple fibroids, and submucosal fibroids increase the risk more than intramural or subserosal ones.
- First-trimester bleeding: Higher risk in women with submucosal fibroids.
- Placental abruption: Higher risk in women with submucosal and large uterine fibroids.
- Preterm labor.
- Abnormal fetal presentation and dystocia: Large, multiple fibroids—especially those located in the lower uterine segment—increase the likelihood of abnormal fetal presentation and labor difficulties.
- Postpartum hemorrhage: Large fibroids, especially intramural ones, may prevent the uterus from contracting properly after delivery due to disruption of the myometrial fiber architecture.
Management of fibroids during pregnancy depends on the clinical symptoms they cause. In most cases, treatment is conservative, while in rare cases, surgical intervention may be necessary.
Management of fibroids during pregnancy depends on the clinical symptoms they cause. In most cases, treatment is conservative, while in rare cases, surgical intervention may be necessary.
It has also been observed that the rates of spontaneous miscarriages increase significantly in pregnant women with fibroids compared to those without (14% versus 7.6%, respectively). The mechanism by which fibroids cause spontaneous miscarriages remains unclear.
Bleeding in the early stages of pregnancy may be related to the location of the fibroid. The frequency of first-trimester bleeding is significantly higher in pregnancies where the placenta implants over or near a fibroid, compared to pregnancies in which there is no contact between the placenta and the fibroid.
Regarding preterm labor and premature rupture of membranes, pregnant women with fibroids are much more likely to deliver preterm than women without fibroids (16.1% versus 8.7% and 16% versus 10.8%, respectively). In cases of multiple fibroids that come into direct contact with the placenta, the risk of preterm delivery appears to be substantially increased. In contrast, fibroids do not seem to be a risk factor for premature rupture of membranes.
Fetal growth does not appear to be significantly affected by the presence of uterine fibroids. However, research shows that pregnant women with fibroids have a slightly increased risk of delivering a baby with intrauterine growth restriction (IUGR).
In addition, some fetal abnormalities have been reported in women with large submucosal fibroids, such as lateral compression of the fetal skull, abnormal twisting of the fetal neck (torticollis) and defects of the upper and lower limbs.
Finally, pain is the most common complication of fibroids during pregnancy. Symptoms can usually be managed with conservative treatment (rest, hydration, and analgesics), although in rare cases definitive surgical removal may be required.
The obstetrician must always be prepared to recognize and manage any potential complications.
How fibroids are monitored during pregnancy
Many women find out they have a fibroid for the first time at their first-trimester ultrasound. The diagnosis sounds frightening, but in most cases it simply means slightly closer monitoring.
The first ultrasound records four details that shape the plan for the whole pregnancy:
- Number: a single fibroid has a different significance from multiple fibroids.
- Size: fibroids smaller than about 5 centimeters rarely cause problems in pregnancy.
- Location in the uterine wall: submucosal, intramural or subserosal.
- Relation to the placenta and the cervix: the most important factor for the risk of complications and for the mode of delivery.
Based on these, the obstetrician decides how often you will have obstetric ultrasounds. For small fibroids away from the placenta, the standard schedule is usually enough. For large, multiple or retroplacental fibroids, growth scans are added in the third trimester along with assessment of the baby’s position. Rarely, when the picture is unclear, an MRI without contrast may be done.
A practical point: a temporary contraction of the uterine muscle can look like a fibroid on ultrasound. That is why a “new” finding is often rechecked after a few minutes or at the next visit before it is labeled.
Fibroid degeneration in pregnancy: the pain that causes the most concern
As the fibroid grows under the influence of pregnancy hormones, its blood supply may not keep up. Its center dies off, causing what is called degeneration. It usually happens in the second trimester.
How it presents
- Severe, localized pain directly over the fibroid, which is tender to pressure.
- A mild fever and a general feeling of being unwell.
- Nausea or vomiting in some women.
- A mild rise in white blood cells on blood tests.
How it is treated
The diagnosis is made by ultrasound, after ruling out other causes that look similar, such as placental abruption, preterm labor, pyelonephritis or appendicitis. Treatment is conservative: acetaminophen (paracetamol), fluids, rest and, when the pain is very severe, stronger painkillers on medical advice. Anti-inflammatory drugs are given only for a few days, on medical advice, and are avoided in the second half of pregnancy. The pain usually eases within a few days to two weeks. Our detailed guide covers the general approach to abdominal pain in pregnancy in more depth.
Less often, a pedunculated fibroid can twist around its stalk. The pain is then sharp and persistent, and surgery may be needed even during pregnancy.
Fibroids and the placenta: why location matters more than size
Two fibroids of the same size can have completely different effects on a pregnancy, depending on where they are.
- Retroplacental fibroid (beneath the placenta): linked to a higher risk of bleeding, placental abruption and, in some cases, restricted fetal growth. It needs more frequent monitoring.
- Fibroid in the lower part of the uterus or in the cervix: it can prevent the baby’s head from descending, leading to a breech or transverse position and the need for a cesarean section.
- Subserosal fibroid at the top of the uterus (fundus): it usually does not affect the course of the pregnancy, but it can cause pain if it degenerates.
- Submucosal fibroid that distorts the uterine cavity: mainly associated with bleeding and miscarriage in the first trimester.
Planning delivery when you have fibroids
The decision on the mode of delivery is usually made at around 34 to 36 weeks, when the baby’s position and the fibroid’s relation to the cervix can be seen clearly. If the fibroid is not in front of the baby, a vaginal birth is possible and safe.
What is prepared in advance
- Delivery in a maternity hospital with a blood bank, because the risk of bleeding after delivery is higher, especially with large or multiple fibroids.
- Checking hemoglobin and iron stores in the third trimester, so that any anemia can be corrected in time.
- Active management of the third stage of labor, with medications that help the uterus contract.
- If a cesarean section is needed, the surgeon plans the position of the incision to avoid the fibroid.
Pregnancy after a previous myomectomy
If a fibroid was previously removed through a large incision in the uterine wall or by opening the uterine cavity, there is a small but serious risk of uterine rupture during labor. In these cases, a cesarean section is often scheduled shortly before 39 weeks. Pain at the site of the old scar, especially in the third trimester, needs immediate assessment. Tell your obstetrician at your first visit what type of surgery you had.
Warning signs: when to go straight to the maternity hospital
Most pregnant women with fibroids will never need an emergency visit. But do not wait for your next appointment if you develop:
- Abdominal pain that does not ease with acetaminophen (paracetamol) and rest within a few hours.
- A fever of 38°C or higher.
- Any vaginal bleeding, especially after 20 weeks.
- A hard, constantly painful abdomen, which may mean placental abruption.
- Regular contractions or pelvic pressure before 37 weeks.
- Reduced fetal movements.
- Dizziness, a racing heart or severe fatigue, which may point to anemia or internal bleeding.
If you have a history of myomectomy, add to this list any new, persistent pain at the scar site.
After delivery: what happens to the fibroids
In the weeks after birth, as the uterus returns to its normal size and pregnancy hormones fall, most fibroids shrink. In some women they shrink considerably.
- Postpartum period: postpartum bleeding (lochia) may last a little longer or be heavier. Tell your doctor if the bleeding suddenly increases or large clots appear.
- Breastfeeding: fibroids do not affect breastfeeding, and breastfeeding helps the uterus contract.
- Reassessment: an ultrasound about three months after delivery shows the true size of the fibroids.
Only then does it make sense to discuss treatment, if the fibroids cause symptoms or you are planning another pregnancy. The options, from monitoring to minimally invasive techniques, are described in detail in our guide on uterine fibroids.
Should a fibroid be removed before pregnancy?
What we know is that pregnancy can increase the size of a fibroid, because the estrogen levels that rise during pregnancy tend to stimulate its growth.
A woman with a uterine fibroid who is planning a pregnancy or wants to undergo in vitro fertilization should discuss with her gynecologist whether the fibroid needs to be removed, so that problems do not arise later in the course and outcome of the pregnancy.
If a fibroid is small and located on the outside of the uterus, it is not necessary to remove it before pregnancy. However, when it is inside or near the uterine cavity, removal is recommended since—aside from making conception more difficult—it may grow larger due to pregnancy hormones and negatively affect the pregnancy.
When is pregnancy possible after fibroid removal surgery?
After undergoing fibroid removal surgery, a woman can usually become pregnant 4 to 6 months later. If the fibroid is pedunculated and does not affect the uterine body, pregnancy may be allowed sooner.
Finally, it is important to emphasize that even if fibroids do not cause problems, they should not be allowed to grow too large, as the treatment options become more limited. In general, a fibroid larger than 5 centimeters is best removed, regardless of whether it causes symptoms or not.
Treatment & Management
As a rule, fibroids inside the uterine cavity are treated with hysteroscopic removal, while the other fibroids are usually treated with laparoscopy or robotic surgery.
Frequently Asked Questions
Do fibroids grow during pregnancy?
Most stay the same size. About one in three grows, mainly in the first trimester, and often shrinks again after delivery.
Can they cause miscarriage or preterm labor?
The risk rises slightly when fibroids are large, multiple or distort the uterine cavity. Most women with fibroids have a normal pregnancy.
Why does a fibroid hurt during pregnancy?
When it grows quickly, it may not get enough blood supply and can degenerate, causing severe localized pain. It is managed with rest and suitable painkillers. Any abdominal pain in pregnancy should be reported to your doctor.
Will I have a vaginal birth or a cesarean section?
A vaginal birth is possible in most cases. A cesarean section is needed when the fibroid blocks the baby’s way out or when the baby is in an abnormal position.
Are fibroids removed during pregnancy or during a cesarean section?
As a rule, no, because of the risk of bleeding. Treatment is planned after delivery. See the treatment options for uterine fibroids.
Do fibroids affect the baby’s health?
In the vast majority of cases, no. The baby’s growth is usually normal. The risk of growth restriction rises slightly only with large or multiple fibroids beneath the placenta, which is why extra growth scans are done in that case.
How often do I need an ultrasound if I have a fibroid during pregnancy?
For small fibroids away from the placenta, the standard ultrasound schedule is usually enough. For large, multiple or retroplacental fibroids, growth scans are added in the third trimester, at intervals set by your obstetrician.
Can I have a vaginal birth if I have had a myomectomy?
It depends on the type of surgery. After removal of a pedunculated or subserosal fibroid without a deep incision, a vaginal birth is usually possible. If the incision was deep or the uterine cavity was opened, a planned cesarean section is usually recommended.
Can a fibroid cause bleeding after delivery?
Yes, large fibroids can prevent the uterus from contracting properly. That is why delivery takes place in a maternity hospital with a blood bank, medications that help the uterus contract are given preventively, and the mother is closely monitored for the first few hours.
What kind of painkiller is allowed for fibroid pain during pregnancy?
Acetaminophen (paracetamol) is the first choice throughout pregnancy. Anti-inflammatory drugs are given only on medical advice, for a few days, and are avoided in the second half of pregnancy. If the pain is not controlled with simple measures, you need to be assessed at the maternity hospital.
