Uterine fibroid(s) in pregnancy

1. What is fibroid?
  • Uterine fibroid is benign tumour that grows from the muscle wall (myometrium) of the womb (uterus). It is also known as uterine fibroma;
  • Approximately 20-30% of women between 30-50 years of age do have fibroids in their uterus;
  • Based on the location at the uterine wall, fibroids are given different names:
  1. (i) Intramural- grow mainly within the muscle wall
  2. (ii) Subserosal- grow on the outside of the uterine wall
  3. (iii) Submucosal- grow in the inner layer of the uterus towards the uterine cavity
  • One can have a solitary fibroid while some can have multiple ones;
  • Uterine fibroids can be of different sizes, ranging from < 1cm to > 10cm;
  • The chance of turning malignant is very low, only in the order of ~1 in 500 to 700
2. Is it common to have fibroid?
  • It is common- approximately 20-30% of women between 30-50 years of age;
  • Most do not have symptom and are only picked up on ultrasound scan
3. Has pregnancy got any effect(s) on the fibroid(s)?
  • The fibroid(s) may increase in size during pregnancy. The rise of oestrogen level associated with pregnancy is thought to be the underlying cause. Usually the size will reach maximum at around 20 weeks of gestation. The growth afterward should be minimal. Following delivery, the fibroid(s) usually shrink back to its original pre-pregnancy size gradually as the level of oestogen drops;
  • Larger fibroids (usually > 5 cm) may undergo ‘red degeneration’. It is thought to be due to the rapid growth of the fibroid, which has outgrown its blood supply. The insufficient blood supply causes infarction of the fibroid and hence it looks ‘red’ if cut open. Acute severe pain at the site of the fibroid is the usual symptom.
4. Has the fibroid(s) got any effect(s) on the pregnancy?
  • Usually no effect. Most fibroids do not cause problem in pregnancy;
  • Sometimes the fibroid is located at the lower part of the uterus or cervix, it may block the birth canal, increasing the chance of non-vertex fetal presentation at term and the need for caesarean section;
  • Large fibroid may occasionally affect the uterine contraction after delivery, leading to more blood loss. When required, medication can be used to enhance the uterine contraction following childbirth.
5. Does the fibroid(s) affect the fetus?
No. Fibroid will not compete with the fetus for nutrition or compress the fetus causing harm.

6. Does the fibroid(s) need to be removed if caesarean section is performed?
It is a common question as it seems ‘convenient’ to remove the fibroid as the tummy is already laid open during the caesarean section. However, the traditional way is NOT to remove the fibroid at the same time. The blood vessels are much larger at term pregnancy and can bleed more. For large fibroids, control of bleeding is particularly a concern. For small fibroids, they will shrink after delivery and may not need to be removed anyway. However, there might be exceptional cases where removal of the fibroid is feasible and justified. A careful planning and counselling are important for such decision.
This article is contributed by Dr. T.N. Danny Leung
Updated on 25.09.2020