- Fibroids are common, benign growths and most do not complicate pregnancy.
- The location of the fibroid is more important than its size.
- Submucosal fibroids, which impinge on the uterine cavity, are the most problematic.
- Your care team will monitor fibroid size and position during your pregnancy scans.
What Are Fibroids, and Why Do They Matter?
Fibroids, or uterine leiomyomas, are extremely common benign tumours of the muscular wall of the uterus. Their growth is fuelled by oestrogen, and they affect a large number of women, often without causing any symptoms at all.
Many women in the UK only discover they have fibroids when they have an ultrasound scan for an unrelated reason, or during their routine first-trimester pregnancy scan. For most, they are a harmless finding. However, depending on their size and location, they can sometimes have an impact on fertility and pregnancy.
How Fibroids Can Affect Pregnancy
The primary concern with fibroids is their location. A fibroid that grows into the uterine cavity (submucosal) can interfere with the implantation of an embryo or the development of the placenta, increasing the risk of miscarriage or bleeding.
Fibroids located within the uterine wall (intramural) or on the outer surface (subserosal) are less likely to cause issues, unless they grow very large. Large fibroids can sometimes cause pain due to degeneration, or in late pregnancy, they might affect the baby's position or block the birth canal, which could mean a caesarean delivery is needed.
Management Before and During Pregnancy
If you know you have large or submucosal fibroids before trying to conceive, we may discuss treatment options such as a myomectomy (surgical removal). This is a significant operation, and the decision depends on balancing the risks of surgery against the potential pregnancy risks posed by the fibroids.
If you are already pregnant, fibroids are simply monitored. We watch their growth and the baby's development via ultrasound. If you experience pain, it can usually be managed with simple painkillers. The important thing is to ensure your obstetric team in London, Manchester, or wherever you are based, is aware of them from the start.
Frequently asked questions
Do fibroids mean I will have a complicated pregnancy?
Fibroids are very common, non-cancerous growths of the uterine muscle. Most women with fibroids have perfectly normal pregnancies and deliveries. They are often found incidentally during early NHS pregnancy scans.
Does the size and location of my fibroids matter?
The location is key. Submucosal fibroids, which grow into the uterine cavity, are most likely to affect implantation and increase miscarriage risk. Intramural (in the muscle wall) and subserosal (on the outside) fibroids are less likely to cause problems unless they are very large.
Can fibroids grow or cause pain during pregnancy?
Sometimes. During pregnancy, the increase in hormones can cause fibroids to grow, which may lead to pain or discomfort. In some cases, they can outgrow their blood supply, causing a painful process called 'red degeneration'.
Will I need a caesarean section if I have fibroids?
This depends on their size and location. Large fibroids low down in the uterus can potentially block the baby's exit, making a caesarean section necessary. Your obstetric team will monitor this with ultrasound scans as you approach your due date.
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