Doppler assessment of the aortic isthmus in fetuses with intrauterine growth restriction and placental insufficiency
Aim
To study the aortic isthmus (AoI) circulation in preterm growth-restricted fetuses (IUGR).
Method
Fifty one IUGR fetuses with either an umbilical artery (UA) pulsatility index (PI)>95th centile or a cerebroplacental ratio <5th centile at 24–36 weeks gestation were examined. AoI absolute velocities (end-diastolic velocity (EDV), peak systolic velocity (PSV) and time-averaged maximum velocity (TAMXV)) and PI were compared to reference ranges. Fetuses were also stratified into two groups according to the direction of the diastolic flow in the AoI: 1) antegrade, 2) retrograde. Adverse outcome was defined as perinatal death, respiratory distress syndrome, bronchopulmonary dysplasia, intraventricular hemorrhage (grade III–IV) and necrotising enterocolitis.
Results
AoI absolute velocities showed values of PSV, EDV and TAMXV <5th centile in 40/51, 10/51 and 48/51 cases, respectively. AoI PI > 95th centile was shown in 21/51 cases (41%). No adverse perinatal outcome was significantly associated with neither a high PI or low absolute velocities. Comparing group 1 (anterograde) and group 2 (retrograde), significant differences were found in birth weight (p < 0.01), gestational age at delivery (p < 0.001), UA pH values (p < 0.001) and need of mechanical ventilation (p < 0.01). Perinatal mortality was higher in group 2 than in group 1 (5.7% vs 60%; p < 0.001). A significant correlation (p < 0.001) was found between retrograde flow in the AoI and adverse perinatal outcome.
Conclusion
The decrease in AoI absolute velocities is likely to reflect a decrease in AoI blood flow. Retrograde blood flow in the AoI is clearly related to adverse perinatal outcome.
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