Fetal Doppler reference ranges (gestational-age specific) for umbilical artery, middle cerebral artery, cerebroplacental ratio, and ductus venosus waveforms
Gestational-age–specific umbilical artery pulsatility index (UA-PI) and umbilical artery resistance index (UA-RI) reference intervals can be taken from INTERGROWTH-21st centiles (healthy, low-risk pregnancies). INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
Gestational-age–specific reference standards for middle cerebral artery (MCA-PI), cerebroplacental ratio (CPR), and ductus venosus (DV) A-, S-, and V-wave patterns are published as centile-based charts or qualitative waveform criteria in specialized fetal-hemodynamic references, with abnormality typically defined by extreme centiles (commonly ≤5th or ≥95th) or loss of forward/“true reversal” of the A-wave. [1], [2], ISUOG Doppler in the ductus venosus (qualitative waveform abnormality)
Umbilical artery pulsatility index (UA-PI): normal and abnormal gestational-age centiles (INTERGROWTH-21st)
Reference interval values below are INTERGROWTH-21st centiles for UA-PI (gestational age shown as weeks+days). INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
Abnormal (high resistance pattern): UA-PI ≥95th centile. INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
| Gestational age | 5th centile | 50th centile | 95th centile |
|---|---|---|---|
| 24+0 | 0.86 | 1.10 | 1.38 |
| 25+0 | 0.84 | 1.08 | 1.37 |
| 26+0 | 0.81 | 1.07 | 1.35 |
| 27+0 | 0.79 | 1.05 | 1.34 |
| 28+0 | 0.78 | 1.03 | 1.32 |
| 29+0 | 0.76 | 1.01 | 1.30 |
| 30+0 | 0.73 | 0.99 | 1.28 |
| 31+0 | 0.71 | 0.97 | 1.27 |
| 32+0 | 0.68 | 0.96 | 1.25 |
| 33+0 | 0.66 | 0.95 | 1.24 |
| 34+0 | 0.64 | 0.93 | 1.23 |
| 35+0 | 0.62 | 0.91 | 1.21 |
| 36+0 | 0.60 | 0.89 | 1.19 |
| 37+0 | 0.59 | 0.88 | 1.18 |
| 38+0 | 0.57 | 0.86 | 1.16 |
| 39+0 | 0.55 | 0.84 | 1.14 |
| 40+0 | 0.53 | 0.82 | 1.12 |
INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
Umbilical artery resistance index (UA-RI): normal and abnormal gestational-age centiles (INTERGROWTH-21st)
Reference interval values below are INTERGROWTH-21st centiles for UA-RI (gestational age shown as weeks+days). INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
Abnormal (high resistance pattern): UA-RI ≥95th centile. INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
| Gestational age | 5th centile | 50th centile | 95th centile |
|---|---|---|---|
| 24+0 | 0.60 | 0.69 | 0.78 |
| 25+0 | 0.58 | 0.68 | 0.77 |
| 26+0 | 0.57 | 0.67 | 0.77 |
| 27+0 | 0.56 | 0.67 | 0.76 |
| 28+0 | 0.55 | 0.66 | 0.76 |
| 29+0 | 0.55 | 0.65 | 0.75 |
| 30+0 | 0.54 | 0.64 | 0.75 |
| 31+0 | 0.53 | 0.63 | 0.74 |
| 32+0 | 0.52 | 0.63 | 0.73 |
| 33+0 | 0.51 | 0.62 | 0.72 |
| 34+0 | 0.50 | 0.61 | 0.71 |
| 35+0 | 0.49 | 0.60 | 0.70 |
| 36+0 | 0.48 | 0.59 | 0.69 |
| 37+0 | 0.47 | 0.58 | 0.68 |
| 38+0 | 0.46 | 0.57 | 0.67 |
| 39+0 | 0.45 | 0.56 | 0.66 |
| 40+0 | 0.44 | 0.55 | 0.65 |
INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
Middle cerebral artery PI (MCA-PI): normal and abnormal reference thresholds
MCA-PI reference ranges for serial assessment have been published as gestational-age longitudinal reference curves. [1]
Abnormal (brain-sparing pattern): MCA-PI ≤5th centile is commonly used as the abnormal threshold in gestational-age–specific charts for fetal redistribution. [1]
Cerebroplacental ratio (CPR): normal and abnormal reference thresholds
CPR reference ranges and longitudinal gestational-age equations have been published alongside MCA-PI and UA-PI. [1]
Abnormal: CPR ≤5th centile is commonly used to identify reduced cerebroplacental resistance consistent with fetal redistribution. [1]
Ductus venosus (DV) A-, S-, and V-wave patterns: normal and abnormal waveform criteria
DV waveform interpretation is based on whether the atrium-contraction (A-wave) component remains forward versus becoming absent or reversed. ISUOG Doppler in the ductus venosus (qualitative waveform abnormality)
Normal DV waveform pattern (typical):
- A-wave shows forward flow above the baseline. ISUOG Doppler in the ductus venosus (qualitative waveform abnormality)
- The waveform is triphasic across the cardiac cycle (ventricular systole S component, early diastole component, and atrial contraction A component). [2]
Abnormal DV waveform pattern:
- Absent or reversed A-wave is considered abnormal, reflecting impaired fetoplacental hemodynamics. ISUOG Doppler in the ductus venosus (qualitative waveform abnormality)
- DV reference values for flow velocities and waveform indices have been quantified across early gestation in low-risk cohorts (10–20 weeks). [2]
Practical limitations for “gestational-age-specific ranges” across these parameters
UA-PI and UA-RI gestational-age centiles can be provided directly as tabulated week-by-week values using INTERGROWTH-21st. INTERGROWTH-21st UA Doppler centiles (AJOG 2020)
Numeric gestational-age–specific tables for MCA-PI and CPR require using a specific published reference chart with equations or centile tables (for example, Ebbing et al. longitudinal reference ranges). [1]
DV A-, S-, and V-wave interpretation is primarily waveform-shape based (normal triphasic forward A-wave versus absent/reversed A-wave) rather than a single numeric PI/RI interval, although DV velocity-based indices have published reference ranges. ISUOG Doppler in the ductus venosus (qualitative waveform abnormality), [2]