How often should uterine fibroids be monitored via ultrasound in a 20-week pregnant woman?

Ultrasound Monitoring of Uterine Fibroids During Pregnancy

For a 31-year-old woman at 20 weeks of pregnancy with three uterine fibroids, ultrasound monitoring should be performed at the time of diagnosis and then again in the third trimester (32-34 weeks) to evaluate fibroid growth and assess potential complications.

Initial Assessment

• Uterine fibroids are common benign tumors occurring in approximately 10.7% of pregnant women 1.
• The initial ultrasound assessment should thoroughly document:
  • Number, size, and location of fibroids (submucosal, intramural, or subserosal) 2
  • Relationship of fibroids to the placenta 1
  • Any distortion of the uterine cavity 2

Monitoring Schedule

• After initial documentation at 20 weeks, a follow-up ultrasound should be performed in the third trimester (≥32 weeks) to:
  • Reassess fibroid size and growth 2
  • Evaluate fetal growth 2
  • Detect potential complications 2
  • Plan for appropriate delivery management 1

Rationale for This Schedule

• Most fibroids do not significantly increase in size during pregnancy despite common belief 1, 3.
• The third-trimester ultrasound is critical as 15% of fetal anomalies are only detected during this period 2.
• For fibroids that may affect delivery planning, assessment at ≥32 weeks provides timely information for obstetric decision-making 2.

Special Considerations

• Additional ultrasounds may be indicated if the patient develops:
  • Acute abdominal pain (possible red degeneration) 1, 4
  • Vaginal bleeding 4
  • Signs of preterm labor 4
  • Significant growth in fibroid size between scheduled ultrasounds 2

Potential Complications to Monitor

• Fibroids can affect pregnancy in several ways that should be assessed during ultrasound monitoring:
  • Miscarriage risk (34% may experience threatened miscarriage) 4
  • Preterm labor (occurs in approximately 21% of cases) 4
  • Malpresentation due to mechanical obstruction 1
  • Placental abnormalities if fibroids are near the placental implantation site 1
  • Intrauterine growth restriction 2, 4

Delivery Planning

• The third-trimester ultrasound is crucial for delivery planning as fibroids may influence:
  • Route of delivery (85% of women with fibroids may require cesarean section) 4
  • Risk of postpartum hemorrhage (occurs in approximately 4% of cases) 4
  • Need for additional interventions during delivery 1

Key Points to Remember

• Ultrasound is the primary imaging modality for monitoring fibroids during pregnancy 2.
• Color Doppler assessment helps differentiate fibroids from myometrial thickening 1.
• Most fibroids remain stable or may even decrease in size during pregnancy 3.
• The location of fibroids relative to the placenta and cervix is more clinically significant than their absolute size 1, 4.