1. Introduction
Uterine fibroids (leiomyomas or myomas) are benign smooth muscle tumors of the uterus. They are the most common benign tumors in women of reproductive age, with an estimated incidence of up to 70% in certain populations 111. During pregnancy, the hormonal milieu (high estrogen and progesterone levels) and increased uterine vascularity can lead to rapid growth of fibroids. Often, these fibroids may outstrip their blood supply, causing degenerative changes.
Among the various possible degenerations, red (carneous) degeneration is the most frequently encountered during pregnancy and can lead to hemorrhage and pain, two of the most significant complications. Understanding the specific mechanisms driving these complications helps guide clinical management and prevent adverse outcomes for both mother and fetus.
2. Types of Myoma Degeneration in Pregnancy
Fibroids commonly undergo degenerative changes when their blood supply becomes insufficient to meet the demands of an enlarging tumor. This can happen especially during pregnancy because the uterus grows rapidly, and while overall blood flow increases, certain fibroids may still be prone to ischemia due to their size, location, or vascular pattern.
The main types of fibroid degeneration include:
Type of Degeneration | Pathophysiology | Symptoms |
Red (Carneous) Degeneration | Venous thrombosis within the fibroid leads to hemorrhagic infarction. More common in pregnancy due to increased estrogen and progesterone. | Severe pain, localized tenderness, low-grade fever, leukocytosis |
Hyaline Degeneration | Replacement of smooth muscle cells with a homogeneous eosinophilic substance due to chronic ischemia. | Usually asymptomatic, but large fibroids may cause pressure symptoms |
Cystic Degeneration | Liquefaction of fibroid tissue leads to fluid-filled (cystic) spaces. | Pain and possible mass effect symptoms |
Myxoid Degeneration | Excessive mucopolysaccharide deposition softens the fibroid. | Soft, gelatinous mass, can cause pressure symptoms |
Calcific Degeneration | Deposition of calcium in the fibroid, often seen in long-standing fibroids. | Rare in pregnancy, usually observed in older women; often asymptomatic |
Among these, the red (carneous) degeneration is the most commonly encountered type of degeneration during pregnancy and is chiefly responsible for the acute onset of hemorrhage and pain.
3. Mechanisms of Hemorrhage and Pain
3A. Hemorrhage
Vascular Compromise & Venous Thrombosis
During pregnancy, the uterus receives significantly more blood flow to support fetal development. However, fibroids can become relatively under-perfused, especially larger fibroids or those with poor vascularization patterns.
Venous thrombosis develops within the fibroid’s vessels, leading to hemorrhagic infarction (red degeneration).
The infarcted tissue may bleed internally, causing localized hematoma formation within or around the fibroid.
Necrosis & Breakdown of Fibroid Tissue
As the fibroid undergoes ischemia from compromised blood supply, tissue necrosis ensues.
Necrotic fibroid tissue can bleed into the tumor’s substance, resulting in internal hemorrhage within the fibroid.
In some cases, this process may extend to the uterine cavity if the fibroid is submucosal, leading to vaginal bleeding.
Disruption of Endometrial Blood Vessels
Submucosal fibroids that bulge into the uterine cavity can disrupt overlying endometrial vessels, causing vaginal hemorrhage.
If the hemorrhagic infarction extends through the myometrium into the endometrium, it can lead to notable bleeding into the uterine cavity.
3B. Pain
Ischemia and Necrosis of Fibroid Tissue
Insufficient blood supply leads to ischemic pain, which is typically sudden in onset and can be severe.
The necrosis of tissue activates local pain receptors and can also elicit a systemic inflammatory response, contributing to low-grade fever and leukocytosis.
Inflammatory Response
The body’s immune response to necrotic tissue involves the release of cytokines, prostaglandins, and other inflammatory mediators.
Elevated prostaglandin levels can increase uterine contractility, compounding the pain and even raising the risk of preterm labor if the irritability spreads through the uterus.
Uterine Contractions & Increased Pressure
As the pregnancy progresses, the growing uterus puts additional mechanical stress on fibroids.
This stretching tension can worsen ischemia or cause discomfort by irritating nerve fibers within or near the fibroid.
Pain can present as cramping and may mimic other obstetric causes of abdominal pain.
Compression of Surrounding Structures
Large fibroids or fibroids with an exophytic growth pattern can compress adjacent organs (e.g., bladder, bowel, ureter).
This compression can lead to pelvic pressure, urinary frequency, or obstructive symptoms, indirectly causing or exacerbating pain.
4. Clinical Presentation
Pain: Sudden onset, severe, localized to the area of the fibroid. Often described as sharp or stabbing.
Tenderness: The fibroid or the uterus may be tender on palpation.
Low-Grade Fever: A temperature elevation typically <38.5°C due to localized inflammation and necrosis.
Leukocytosis: Mild elevation in white blood cell count in response to inflammation or necrosis.
Vaginal Bleeding: More common if the fibroid is submucosal or if necrotic changes extend into the uterine cavity.
Although these signs and symptoms are relatively nonspecific, the sudden onset of localized uterine pain in a pregnant woman with a known fibroid is highly suggestive of red degeneration.
5. Differential Diagnoses
Pregnant women presenting with acute abdominal pain should be evaluated for several differential diagnoses, including:
Round Ligament Pain
Commonly presents as a sharp pain on the side of the uterus, but typically not associated with fever or leukocytosis.
Placental Abruption
Presents with vaginal bleeding (in most cases), uterine tenderness, and often fetal distress. It is a critical emergency.
Ovarian Torsion
Typically presents with sudden onset, severe unilateral pelvic pain, sometimes with nausea/vomiting. Doppler ultrasound can help differentiate by showing decreased ovarian blood flow.
Appendicitis
Right lower quadrant (RLQ) or right upper quadrant (RUG) pain in later pregnancy, often with systemic signs such as fever, elevated inflammatory markers.
Pyelonephritis
Flank pain, fever, and urinary symptoms are more common; tenderness is usually costovertebral.
Other Gastrointestinal Causes
Bowel obstruction, cholecystitis, or pancreatitis can also present with abdominal pain and systemic symptoms.
6. Diagnosis
Ultrasound (USG)
The first-line imaging modality.
Degenerating fibroids may appear heterogeneous or hypoechoic with possible cystic or hemorrhagic areas.
Use of Doppler may show reduced blood flow in the affected areas.
Magnetic Resonance Imaging (MRI)
Offers greater sensitivity in differentiating fibroid degeneration from other pathologies (e.g., adenomyosis, malignancy).
Especially useful if ultrasound findings are inconclusive or if a complex adnexal mass or other pelvic pathology is suspected.
Doppler Studies
May show reduced or absent flow in the affected fibroid segment, aiding in the confirmation of red degeneration.
Laboratory Tests
Complete Blood Count (CBC): May reveal mild leukocytosis.
Inflammatory Markers (CRP, ESR): Can be elevated during acute degeneration.
7. Management
7A. Conservative (First-Line)
Pain Control
Acetaminophen (Paracetamol): Safe in all trimesters of pregnancy.
NSAIDs (e.g., Ibuprofen, Indomethacin): Generally used with caution and typically avoided in the 3rd trimester due to the risk of premature closure of the ductus arteriosus and other fetal complications.
Opioids: Reserved for severe pain when other measures are insufficient, under strict supervision.
Rest & Hydration
Adequate hydration and bed rest can help reduce uterine irritability and contractions.
Tocolytics (if preterm contractions occur)
Nifedipine: A calcium channel blocker that can reduce uterine contractions.
Indomethacin: An NSAID-based tocolytic, but typically avoided after 32 weeks of gestation.
Magnesium Sulfate: Sometimes used for neuroprotection of the fetus (in very preterm labor) and can have a tocolytic effect.
Monitoring
Serial abdominal exams to ensure the pain and tenderness are improving.
Fetal monitoring to check for signs of distress or preterm labor.
Follow-up ultrasounds to evaluate fibroid size and resolution of degenerative changes.
7B. Surgical (Rare)
Myomectomy
Surgical removal of fibroids is generally avoided during pregnancy due to the risk of severe hemorrhage and potential harm to the pregnancy.
It may be considered only in extreme cases where there is intractable pain unresponsive to medical management, or when uncontrolled hemorrhage threatens maternal hemodynamic stability.
Cesarean Delivery with Concurrent Myomectomy
Sometimes performed at term or near term if the fibroid is subserosal or pedunculated and easily accessible.
However, the decision is individualized based on the size, location, and degree of fibroid vascularity.
8. Potential Complications
Preterm Labor: Excessive uterine irritability and contractions triggered by degenerating fibroids can lead to preterm cervical changes.
Chorioamnionitis (rare): In cases of severe infection secondary to necrotic tissue and infiltration by pathogens.
Acute Hemodynamic Instability: If a large fibroid bleeds significantly, resulting in hypovolemia.
Adverse Fetal Outcomes: Fetal growth restriction or abnormal fetal lie/presentation if large fibroids distort the uterine cavity.
9. Summary
Degenerative fibroids in pregnancy often undergo red (carneous) degeneration, which primarily presents with hemorrhage and significant pain. These complications arise from vascular compromise, leading to ischemia, venous thrombosis, and necrosis within the fibroid. The ensuing inflammatory response and local tissue breakdown exacerbate pain and can incite uterine contractions, posing risks such as preterm labor.Most cases are managed conservatively with pain control, rest, and, where necessary, tocolytics. Surgical intervention is rare but may be essential if there is uncontrolled hemorrhage or severe complications. A thorough differential diagnosis is crucial given the range of acute abdominal and pelvic pathologies in pregnancy. With vigilant management, outcomes for both mother and fetus are generally favorable.
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