Increased Ductus Venosus Pulsatility Index on Fetal Ultrasound
An increased ductus venosus pulsatility index (PI) is defined as a value above the 95th percentile for gestational age, though abnormality is primarily determined by qualitative waveform analysis showing decreased, absent, or reversed flow during atrial contraction (the A-wave), rather than by PI percentile alone. 1
Primary Definition of Abnormality
The most clinically significant abnormality in ductus venosus Doppler assessment is qualitative waveform analysis, not the PI percentile:
- Decreased, absent, or reversed flow in the A-wave (during atrial contraction) represents the key abnormal finding linked to adverse outcomes 1
- This waveform abnormality indicates myocardial impairment and increased ventricular end-diastolic pressure from elevated right ventricular afterload 1
- These abnormal waveforms are directly linked to neonatal acidemia and perinatal mortality in growth-restricted fetuses 1
Pulsatility Index Percentile Thresholds
When PI values are used quantitatively, the following thresholds define abnormality:
- >95th percentile is the standard cutoff for abnormally increased ductus venosus PI 2, 3
- >90th percentile has been associated with increased risk for chromosomal abnormalities, small for gestational age infants, and low birth weight 4
- In first-trimester screening for trisomy 21,73% of affected fetuses showed PI values >95th percentile 2
Clinical Context and Timing
The interpretation varies by gestational age and clinical scenario:
- First trimester (10-18 weeks): Increased PI >95th percentile is associated with chromosomal abnormalities, particularly trisomy 21, and predicts later fetal growth restriction 2, 4
- Second and third trimester (≥23 weeks): Focus shifts to qualitative A-wave assessment in growth-restricted fetuses, where abnormal waveforms indicate cardiovascular decompensation 1
- Normal ductus venosus shows continuous forward flow throughout the cardiac cycle with a biphasic waveform pattern 1
Important Technical Considerations
Common pitfalls to avoid:
- Mistaking the inferior vena cava for the ductus venosus is the most frequent technical error 1
- Proper identification requires color Doppler showing aliasing (mixture of colors) at the site where the ductus venosus branches from the umbilical vein 1
- Measurements should be obtained in transverse or sagittal views of the fetal abdomen at the diaphragm level 1
Clinical Significance
The strength of evidence prioritizes waveform morphology over PI percentiles because:
- Abnormal A-wave flow has direct correlation with neonatal acidemia and mortality in intrauterine growth restriction 1
- This represents late-stage cardiovascular compromise requiring urgent clinical decision-making 1
- PI percentiles are more useful for early screening (first trimester) rather than acute fetal assessment 2, 4
In practice, when evaluating a growth-restricted fetus, the presence of absent or reversed A-wave flow is more clinically actionable than a mildly elevated PI percentile, as it indicates imminent cardiovascular decompensation requiring delivery consideration. 1