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In most cases, they don’t cause serious problems, but depending on their size and location, they can sometimes affect how your pregnancy feels or progresses. Many women with fibroids go on to have completely healthy pregnancies and babies.
What Are Fibroids?
Fibroids (medically called uterine leiomyomas) are non-cancerous growths that develop in or around the walls of the uterus. They're made of muscle and fibrous tissue, and they range in size from a pea to, in rare cases, a grapefruit.
They are not tumours in the dangerous sense of the word. They do not spread, and they are rarely cancerous. Some women have just one; others have several at the same time. They can grow in different locations:
- Submucosal: Inside the uterine cavity (least common, but most likely to affect pregnancy)
- Intramural: Within the uterine wall (most common type)
- Subserosal: On the outside of the uterus (least likely to affect pregnancy)
Their location matters a lot, especially during pregnancy.
Fibroids are incredibly common. Up to 70–80% of women will develop at least one fibroid by the time they reach their 50s. Many remain unaware of them, and they are discovered only when a doctor is looking for something else, like during a prenatal ultrasound.
Why Do Fibroids Show Up (or Grow) During Pregnancy?
Pregnancy floods your body with oestrogen and progesterone – the hormones that help your baby grow. These same hormones also happen to fuel fibroid growth. This is why fibroids that were small or dormant before pregnancy can sometimes enlarge during the first and second trimester.
However, most fibroids don't grow significantly during pregnancy. Studies show that roughly 60–70% of fibroids stay the same size or even shrink. Only about 1 in 3 fibroids grow during the first trimester, and growth often plateaus after that.
Can Fibroids Affect Your Baby?
For the vast majority of pregnancies, fibroids cause no complications for the baby. Most women with fibroids go on to have completely healthy pregnancies and healthy babies.
In a smaller number of cases, particularly with large fibroids or those located near the placenta, there can be some complications.
Potential Risks and How Common They Are:
Placental Abruption
This is when the placenta separates from the uterine wall before delivery. Fibroids, especially large ones near the placenta, can slightly increase this risk. However, placental abruption occurs in approximately 0.4–1% of all pregnancies, and women with fibroids, particularly those located behind the placenta, face a modestly higher risk.Preterm Labour
Some studies suggest that women with fibroids, especially multiple or large ones, have a slightly higher risk of going into labour before 37 weeks. This is one reason your doctor will monitor your pregnancy more closely if fibroids are present.Foetal Growth Restriction
In rare cases, a fibroid positioned near the placenta can compete for blood supply, potentially affecting the nutrient supply reaching the baby. This is more of a concern with large submucosal fibroids.Malpresentation
If a fibroid is large enough, it can physically limit the space in the uterus, making it harder for the baby to settle into the ideal head-down position before delivery. This can sometimes lead to a breech or transverse position, which may increase the chances of a caesarean section.Caesarean Delivery
Women with fibroids are statistically more likely to deliver by C-section, not because fibroids make vaginal birth impossible, but because of factors like malpresentation or the location of fibroids near the lower uterine segment. If a large fibroid is blocking the birth canal, a C-section becomes necessary for safety.How Are Fibroids Monitored During Pregnancy?
If your doctor knows you have fibroids, they will likely recommend more frequent ultrasound scans throughout your pregnancy. This isn't a cause for panic; it's simply good, proactive care that lets your team track any changes in fibroid size, monitor the baby's growth and position, and check the placenta.
You don't need any special tests beyond what's standard for a monitored pregnancy. Ultrasound is safe, non-invasive, and gives your care team everything they need to keep an eye on things.
In most cases, no treatment is needed during pregnancy. Surgery to remove fibroids (myomectomy) is almost always postponed until after delivery because operating during pregnancy carries significant risks. The exception is rare, extreme cases, but these are quite uncommon.
After Delivery: What Happens to the Fibroids?
Fibroids often shrink significantly after delivery. Once pregnancy hormones drop, many fibroids reduce in size, and some disappear entirely. Women who breastfeed may see even more regression, as breastfeeding suppresses oestrogen.
If you still have symptoms after delivery, there are now many effective treatment options, from medication to minimally invasive procedures like uterine fibroid embolisation (UFE), that don't require major surgery.
Fibroids during pregnancy sound scarier than they usually are. For the majority of women, they are bystanders, not a threat, present, perhaps occasionally uncomfortable, but not putting the pregnancy or the baby in danger.
What makes the difference is good monitoring, open communication with your healthcare team, and knowing what signs to watch for.
You can absolutely have a healthy, full-term pregnancy with fibroids. Thousands of women do, every single day.
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FAQs on Fibroids During Pregnancy: Do They Affect Your Baby?
- Can fibroids harm my baby directly?
In most cases, no. Fibroids very rarely affect the baby directly. The main concerns are indirect, such as preterm labour, malpresentation, or (rarely) restricted foetal growth if a large fibroid interferes with placental blood flow. - Should fibroids be removed before trying to get pregnant?
It depends on the type, size, and location. Submucosal fibroids, those inside the uterine cavity, are generally recommended for removal before pregnancy because they have the strongest evidence of affecting implantation and early pregnancy. For other types, the decision should be made with your gynaecologist based on your individual situation. - Can I have a normal vaginal delivery if I have fibroids?
Yes, many women with fibroids deliver vaginally without any issue. A C-section becomes more likely if fibroids are very large, positioned near the cervix or lower uterine segment, or if they've caused the baby to be in a non-ideal position. Your doctor will assess this as your pregnancy progresses.