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Updated: Oct 7, 2026
Fetal Echocardiography and Pulsed-wave Doppler Ultrasound in a Rabbit Model of Intrauterine Growth Restriction
Published on: June 29, 2013
Characterization of growth-restricted fetuses with breakdown of the brain-sparing effect diagnosed by spectral
Y Takahashi1, I Kawabata, T Tamaya
1Department of Obstetrics and Gynecology, Gifu University School of Medicine, Gifu City, Japan. y-taka@cc.gifu-u.ac.jp
Insights
Serial Doppler findings in growth-restricted fetuses reveal distinct patterns. A "breakdown of the brain-sparing effect" in middle cerebral artery (MCA) and umbilical artery (UA) flow patterns predicts severe growth restriction and adverse outcomes.
Area of Science:
- Perinatology
- Fetal Medicine
- Doppler Ultrasound
Background:
- Fetal growth restriction (FGR) is a major cause of perinatal morbidity and mortality.
- Doppler ultrasound assessment of fetal circulation, particularly the middle cerebral artery (MCA) and umbilical artery (UA), is crucial for monitoring FGR.
- Understanding the progression of circulatory changes is key to predicting neonatal outcomes.
Purpose of the Study:
- To characterize serial Doppler flow patterns in the MCA and UA in fetuses with FGR.
- To investigate the relationship between MCA and UA flow patterns.
- To correlate these Doppler findings with neonatal outcomes.
Main Methods:
- Serial pulsatility indices (PIs) of MCA and UA were measured in 41 growth-restricted fetuses.
- Three distinct Doppler patterns were identified: no brain-sparing, brain-sparing effect, and breakdown of the brain-sparing effect.
- Umbilical cord blood gas analysis was performed at delivery for comparison between groups.
Main Results:
- Significant differences in gestational age at delivery and body weights were observed across the three Doppler patterns.
- All fetuses exhibited diminished body weights, confirming growth restriction.
- Phase 3 (breakdown of brain-sparing) was associated with significantly different pH and base excess values, indicating metabolic acidosis.
Conclusions:
- Fetuses exhibiting the "breakdown of the brain-sparing effect" (elevated MCA and UA PIs with absent or reversed end-diastolic flow) were delivered early with severe growth restriction and mild metabolic acidosis.
- A transition from decreased to increased MCA PI, coupled with rising UA PI, may serve as a predictor of severely growth-restricted infants.
- Serial Doppler assessment of MCA and UA flow patterns provides valuable prognostic information in FGR.
Objective:
To characterize serial findings of the middle cerebral artery (MCA) and umbilical artery (UA) flow patterns, their relationship to each other, and neonatal outcomes in growth-restricted fetuses.
Methods:
Serial pulsatility indices (PIs) from MCA and UA Doppler waveforms were measured in 41 growth-restricted fetuses until Cesarean delivery. We found three patterns, as follows: phase 1 (n = 27), UA PI < MCA PI (no brain-sparing effect); phase 2 (n = 11), UA PI > MCA PI (brain-sparing effect); phase 3 (n = 3), both PIs elevated with the absence of end-diastolic flow or presence of reverse end-diastolic flow, which was designated as the 'breakdown of the brain-sparing effect'. Umbilical cord blood gas data at delivery were compared between each group.
Results:
Age at delivery and body weights were significantly different for each phase. The mean body weights in all phases were significantly diminished from Japanese standard body weights, indicating growth restriction. The phase 3 pH and base excess were significantly different from those of the other two phases.
Conclusions:
Growth-restricted fetuses which suffered from the state of breakdown of the brain-sparing effect were delivered early with severe growth restriction and mild metabolic acidosis. The change from decreased to increased MCA PI along with increasing UA PI may predict a severely growth-restricted infant.
