Are serial third trimester growth ultrasounds recommended for a uterus with uterine fibroids (leiomyomas)?

From the Guidelines

Serial third trimester growth ultrasounds are recommended for pregnant women with a fibroid uterus, especially if the fibroids are large (>5 cm) or numerous, to monitor fetal growth and detect potential growth restriction. These ultrasounds should typically be performed every 3-4 weeks starting at around 28 weeks gestation until delivery, as suggested by general clinical guidelines 1. The primary purpose is to monitor fetal growth and detect any potential growth restriction that might occur due to placental insufficiency caused by fibroids. Fibroids can compete with the fetus for blood supply or potentially distort the uterine cavity, which may affect fetal growth. Additionally, these ultrasounds help monitor the fibroids themselves, as they can change in size during pregnancy due to hormonal influences. Some fibroids grow during pregnancy while others may degenerate, causing pain. Serial ultrasounds also help in planning delivery, as large fibroids can obstruct the birth canal or interfere with uterine contractions, potentially necessitating a cesarean section. If growth restriction is detected, more frequent monitoring or earlier delivery might be required depending on the severity of the situation and gestational age.

Key Considerations

• The size and number of fibroids are important factors in determining the need for serial ultrasounds, with larger or more numerous fibroids posing a greater risk to fetal growth 1.
• The American College of Radiology (ACR) provides guidelines for the management of uterine fibroids, including the use of imaging modalities such as ultrasound and MRI 1.
• The Society for Maternal-Fetal Medicine (SMFM) recommends a detailed obstetrical ultrasound examination for the initial diagnosis of fetal growth restriction (FGR), which may be associated with uterine fibroids 1.
• The management of FGR involves serial umbilical artery Doppler assessment and consideration of prenatal diagnostic testing, including chromosomal microarray analysis (CMA) 1.

Monitoring and Management

• Serial ultrasounds should be performed every 3-4 weeks starting at around 28 weeks gestation until delivery to monitor fetal growth and detect potential growth restriction.
• Umbilical artery Doppler assessment should be performed to assess for deterioration in fetal growth.
• Prenatal diagnostic testing, including CMA, should be considered in cases of unexplained isolated FGR diagnosed at <32 weeks of gestation.
• Delivery should be considered at 37 weeks of gestation in pregnancies with FGR and an umbilical artery Doppler waveform with decreased diastolic flow but without absent or reversed end-diastolic velocity (AEDV/REDV) or with severe FGR with estimated fetal weight (EFW) less than the third percentile 1.

From the Research

Serial Third Trimester Growth Ultrasounds for Uterus with Uterine Fibroids

• There is no direct evidence to suggest that serial third trimester growth ultrasounds are recommended specifically for a uterus with uterine fibroids (leiomyomas) 2, 3, 4, 5, 6.
• However, studies have shown that serial third-trimester ultrasound examinations can identify significantly more cases with fetal growth or amniotic fluid abnormalities than routine fundal height measurements 2.
• Uterine fibroids are common benign neoplasms that can cause abnormal uterine bleeding, pelvic pressure, and other symptoms, and ultrasonography is the preferred initial imaging modality for their diagnosis and characterization 3, 4.
• The International Federation of Gynecology and Obstetrics has developed a system for describing and classifying uterine fibroids uniformly and consistently, and an accurate description of fibroids in the ultrasound report is essential for planning surgical treatment and preventing complications 4.
• Routine third-trimester ultrasound can identify fetal abnormalities, including congenital anomalies, and the prevalence of new abnormalities diagnosed is approximately 3.68 per 1000 women scanned 5.
• Third trimester growth restriction patterns can be characterized using a fetal growth pathology score, and individualized assessment can help identify patterns of growth restriction 6.