Can Fibroids Affect Pregnancy? Risks and Management Options

Most women with fibroids have straightforward pregnancies. That’s the starting point worth holding onto, because fibroids are common and the majority cause little to no problems during pregnancy. 

Whether they have any effect depends on the size and location. Fibroids that sit within the uterine cavity are more likely to matter than those in the outer wall, and larger ones more than small ones. Here’s what to understand about fibroids and pregnancy, how they’re monitored during antenatal care, and which situations call for closer attention.

What are fibroids?

Uterine fibroids are non-cancerous growths that develop around or within the uterine wall. They are made of muscle and fibrous tissue, and they could range from very small (about the size of a pea) to relatively large. Fibroids are a common condition in women, yet most cause no symptoms and go unnoticed until a routine scan picks them up.

The exact cause of fibroids is not fully known, but it is likely caused by a combination of factors. Oestrogen and progesterone, the hormones that regulate your menstrual cycle, appear to encourage fibroid growth. This is why fibroids tend to develop during your reproductive years and often shrink after your menopause, when your hormone levels drop naturally.

How can fibroids affect pregnancy?

Fibroids do not always cause problems during pregnancy, and women with fibroids may have healthy pregnancies. However, depending on their size, number, and location, they may sometimes contribute to symptoms or affect how the pregnancy progresses. Some possible concerns include: 

Pain and discomfort

Some women with fibroids may feel pain during pregnancy, particularly during the first and second trimesters. One possible cause is fibroid degeneration, which could happen when a fibroid grows faster than its blood supply could support. When this happens, parts of the fibroid may not receive enough oxygen and nutrients, causing the tissue to break down and trigger inflammation. 

This condition may lead to sudden or sharp pain, which some women describe as feeling similar to painful period cramps but more intense. The discomfort could take different forms, including:

• Persistent pressure or pelvic pain

• Abdominal pain

• Back pain

Bleeding during pregnancy

Fibroids may be associated with a slightly higher risk of vaginal bleeding during pregnancy, particularly during the first trimester. This is because fibroids may affect the uterine lining or the area where the placenta attaches to the womb, which may make bleeding more likely in some pregnancies.

In rare cases, fibroids, particularly those located closer to the placenta, may be associated with placental problems, such as

• Placental abruption:

  • A condition where the placenta partially or completely separates from the wall of the womb before delivery. 

  • Placental abruption could cause heavy vaginal bleeding and may require urgent medical attention.

• Placenta praevia:

  • This occurs when the placenta attaches low in the womb and partially or completely covers the cervix. 

  • It may cause painless vaginal bleeding, particularly during the later stages of pregnancy, and may require closer monitoring as well as careful delivery planning. 

Restricted foetal growth

Larger fibroids may sometimes reduce the space available in the womb as the baby grows. In some cases, this may be associated with restricted foetal growth, also known as foetal growth restriction (FGR), where the baby is smaller than expected for its stage of pregnancy.

Your doctor may recommend the following:

• Closer monitoring during the second and third trimesters, as the baby grows and requires more space.

• Regular ultrasound scans to monitor your baby’s growth and wellbeing if there are concerns.

If you have been diagnosed with fibroids and are concerned about how they may affect your pregnancy, speaking with a gynaecologist may help. Schedule an appointment with Thomson Women's Clinic for a consultation during your pregnancy journey.

Factors that may influence pregnancy risk

Having fibroids does not necessarily mean that you will have a high-risk pregnancy. However, there are other factors that could influence pregnancy risk, including:

Size of fibroids

Although fibroids do not necessarily grow during pregnancy, the size of these growths may affect how much space they occupy in the uterus, as well as whether they press against nearby structures.

• Larger fibroids: particularly those measuring more than 5 cm, have been associated with a higher likelihood of pregnancy complications, including preterm birth, abnormal foetal position, and caesarean delivery. 

• Very large fibroids: more than 10 cm, may take up more space in the womb, which may affect how your baby is delivered. 

Location of fibroids

Where a fibroid is located could be just as important as its size. Fibroids in certain parts of the uterus may have a greater effect on pregnancy, but this does not mean that complications will occur. These may include:

• Fibroids in the lower uterus or cervix may increase the likelihood of the baby being in an unusual position or make vaginal birth more difficult.

• Fibroids located close to the placenta may be associated with a higher risk of bleeding or certain placental complications.

• Fibroids that press against the space where the baby is growing (uterine cavity) may sometimes affect the baby’s position.

Number of fibroids

Multiple fibroids may take up more space within the womb and may contribute to symptoms such as pain or bleeding. However, having multiple fibroids does not necessarily mean you will have a high-risk pregnancy. The overall pregnancy risk depends more on the combined size and location of the fibroids than on the number alone. 

During these routine antenatal care, your obstetrician may use ultrasound and other assessments to monitor the fibroids and determine whether they could affect your pregnancy.

What pregnancy complications are possible?

Most pregnancies involving fibroids progress without major complications, and women with fibroids may go on to have healthy pregnancies and deliver their babies safely. However, depending on the size, number, and location of your fibroids, there may be a slightly higher chance of certain complications. These include:

• Miscarriage: 

  • Fibroids that change the shape of the uterine cavity may be linked to a higher risk of miscarriage. Submucosal fibroids are the type most often associated with this risk.

• Preterm birth:

  • Large or multiple fibroids may make the uterus more sensitive or leave less space for your baby to grow. In some cases, this may increase the risk of labour starting before 37 weeks.

• Placenta problems: 

  • The placenta is the organ that develops during pregnancy to supply your baby with oxygen and nutrients. Fibroids may sometimes affect where and how the placenta attaches in the uterus.

  • This may increase the risk ofplacenta praevia (the placenta sits low in the womb) or placental abruption (the placenta separates from the womb wall early)

• Unusual baby position: 

  • Large fibroids could take up space inside the womb, which may make it harder for your baby to settle into a head-first position.

  • This may increase the chance of a breech position (bottom or feet first) or a transverse lie (lying sideways). If this happens, your doctor may discuss a caesarean delivery closer to your due date to keep both you and your baby safe.

When should you see a doctor?

While your regular appointments allow your doctor to monitor your pregnancy, there are certain symptoms that should be checked without delay. These symptoms do not always mean something serious is wrong, but getting them checked early allows your care team to act quickly if needed. Get checked if you notice:

• Heavy vaginal bleeding

• Severe abdominal pain

• A fever

• Contractions before 37 weeks

• Reduced movement from your baby

Reduced baby movement, in particular, should never be monitored at home. If you notice this, please contact your doctor straight away, rather than waiting for your next appointment.

If you have experienced any of the warning symptoms mentioned above, speaking with a gynaecologist may help you understand the possible cause and receive an early assessment if needed. Schedule an appointment with Thomson Women's Clinic.

How are fibroids managed during pregnancy?

If you have fibroids while pregnant, your doctor will usually focus on regular antenatal care to monitor your pregnancy and manage any symptoms that develop. Your care may include:

• Regular monitoring: 

  • Ultrasound scans may be used to monitor your baby’s growth and assess the size and position of the fibroids. 

  • Your doctor may also check the position of the placenta and recommend more frequent appointments if the fibroids are large or located in an area that could affect pregnancy or delivery.

  • If an ultrasound does not provide enough detail, or if a surgical procedure is being considered, a magnetic resonance imaging (MRI) may be recommended to assess the fibroids more closely, including their size, location and relationship to the placenta.

• Managing pain and discomfort: 

  • Fibroids could sometimes cause pelvic pain or discomfort during pregnancy, particularly if a fibroid undergoes degeneration. 

  • Resting when needed, staying well hydrated and using pregnancy-safe pain medication as advised by your doctor may help relieve symptoms and support pain management during pregnancy.

• Planning for delivery: 

  • Most people with fibroids may give birth without major complications. However, large fibroids or those located near the cervix or birth canal may make vaginal delivery more difficult. 

  • In these situations, your obstetrician may discuss whether a caesarean birth would be safer based on your individual circumstances.

FAQ

Do fibroids grow during pregnancy?

Fibroids may increase in size during pregnancy, particularly during the first trimester when pregnancy hormone levels rise. However, this does not happen with every fibroid. Some may remain the same size, while others may grow temporarily and then stabilise later in pregnancy.

Should fibroids be removed before pregnancy?

Can fibroids cause complications after delivery?

Fibroids may increase the risk of complications such as postpartum haemorrhage (heavier-than-usual bleeding after birth), slower uterine recovery, or a longer recovery after a caesarean birth. However, most women recover well after delivery with appropriate postnatal care.

Will fibroids shrink after pregnancy?

Some fibroids may shrink after pregnancy, particularly as pregnancy-related hormone levels return to their usual levels. However, the amount of shrinkage can vary, and some fibroids may remain similar in size or change very little over time.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and advice based on your individual circumstances, schedule an appointment with Thomson Medical.