Uterine fibroids (leiomyomas) are common, benign tumours of smooth muscle in the uterus affecting 20% of women of reproductive age. ‘Red’ degeneration describes the breakdown of myocytes secondary to ischaemia and is the most common form of fibroid degeneration. It most commonly presents in pregnancy, when fibroids tend to outgrow their blood supply owing to increased circulating oestrogen. Typical presentation is in the second trimester of pregnancy with acute pain and low-grade fever. Management during pregnancy consists of symptom management, and myomectomy can be performed after delivery.


  • Incidence: 50.00 cases per 100,000 person-years
  • Peak incidence: 30-40 years
Condition Relative
Fibroid degeneration1
Placental abruption0.40
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


Growth of fibroids in red degeneration is driven by oestrogen-dependence and is therefore associated with pregnancy.
  • Studies indicate that red degeneration affects 5% of pregnancies
  • Fibroid degeneration in non-pregnant women occurs extremely rarely
  • Key epidemiological risk factor for fibroids include:
    • Commonest in women between 30-50 years
    • Most common in African-Caribbean women


The pathophysiology of fibroids is not entirely clear. However, it is clear that they are oestrogen dependent, and receptors for this hormone bind 20% more oestradiol (E2) than in adjacent myometrium tissue.
  • 15% of pregnant women who have fibroids experience red degeneration during pregnancy, a period of physiological hyper-oestrogenism.
  • Experimental studies suggest that the growth of fibroid tissue under oestrogen influence is related to excessive production of extracellular matrix and hyaline tissue, which interposes between myocyte cells and the capillary beds causing ischaemia (necrobiosis).
  • This then leads to aseptic lysosomal digestion of ischaemic myocytes between areas of hyalinised tissue (cystic degeneration).

Clinical features

Approximately 15% of women with known fibroids experience red degeneration during pregnancy. In other cases, growth and degeneration of fibroids during pregnancy may reveal previously occult fibroids.

  • Fibroid degeneration most commonly occurs in the 12th – 22nd week of pregnancy, and should be considered in women presenting with acute abdominal pain in this period.
  • Acute abdominal pain during pregnancy should be examined urgently.
  • Vaginal bleeding is not a common feature of degeneration and should prompt suspicion of other conditions such as placental abruption.

Abdominal examination:
  • Constant abdominal pain localising to the area of the fibroid
  • Area tender to palpation
  • Rebound tenderness present
  • Fibroid likely palpable as it enlarges
    • Firm and fixed on palpation
    • Assess the fibroid location in relation to the fetal position

Vital signs:
  • Tachycardia and tachypnoea may be present secondary to pain
  • A low-grade fever commonly accompanies fibroid degeneration
  • There should be no haemodynamic compromise or increased oxygen requirement in simple acute fibroid degeneration


Beyond clinical examination, blood tests should be done to check for signs of infection, and foetal monitoring is vital.

Blood tests
  • FBC
    • May show raised WCC
    • Highly elevated WCC and CRP with clinical signs of infection suggests sepsis secondary to infection of degenerating fibroid, a serious condition for both mother and baby

  • Ultrasound
    • Colour-flow doppler can help differentiate fibroids from myometrial thickening
    • Serial ultrasound scans are useful to track developing size and relation to the fetus of fibroid
    • Fibroids in the lower uterine segment are most likely to cause obstruction and complications for the fetus.
  • MR imaging
    • Considered if symptoms continue or exacerbate despite conservative management, and to rule out other diagnoses such as torsion of a pedunculated fibroid if ultrasound is inconclusive
    • MR imaging can map fibroid location and relation to the fetus if surgery is being considered

  • Cardiotocography (CTG)
    • Close monitoring of the fetus for complications
    • Fetal distress is an indication for emergency caesarean section


The management of a degenerating fibroid depends on the severity of the symptoms. Patients with existing fibroids, or with fibroids identified during pregnancy (e.g. during a routine assessment of the fetus) should be counselled about the risks of degeneration, the symptoms suggestive of this, and how to seek medical attention.

Conservative management
The mainstay of treatment is conservative management. The patient will need to be assessed at a centre with obstetrics care. The decision will then be made whether to manage in ambulatory care with regular check-ups or to admit the patient for observation. Patients should be reassured that fibroids usually regress during the puerperium owing to hormonal withdrawal.

  • Analgesia
    • Most cases can be managed at home with simple measures such as paracetamol
    • Some may require hospitalisation and monitoring, with opiate analgesia for severe pain
    • Acute painful episode usually resolves in 4-7 days
    • NSAIDS should be used with caution to avoid fetal complications such as premature closure of the ductus arteriosus

Surgical management
In very rare cases, the decision may be made to remove fibroids in the first or second trimester of pregnancy.
  • Myomectomy
    • Fibroids causing intractable pain or a torted pedunculated fibroid are rare indications for myomectomy, and the risk of intra-operative bleeding is very high
    • Combined caesarean section with myomectomy following delivery of the baby is also not recommended