Bilateral Uterine Artery Elevated RI with Diastolic Notching
Bilaterally elevated uterine artery resistance index with diastolic notching indicates impaired placental perfusion due to failed spiral artery remodeling and significantly increases the risk of fetal growth restriction (FGR) and preeclampsia, but uterine artery Doppler should not guide clinical management—instead, focus surveillance on umbilical artery Doppler and initiate low-dose aspirin if detected before 16 weeks. 1
Clinical Significance and Risk Stratification
What This Finding Means:
Elevated uterine artery RI with bilateral diastolic notching reflects abnormal trophoblastic invasion of maternal spiral arteries, resulting in a high-impedance uteroplacental circulation rather than the normal low-resistance flow pattern. 1
In high-risk women, bilateral notching with elevated RI (>0.58 or >90th percentile) in the second trimester carries a positive likelihood ratio of 10.9 for severe FGR and a likelihood ratio of 9.1-14.6 for IUGR in low-risk women. 1
This finding identifies pregnancies where 58.3% will develop preeclampsia and/or IUGR compared to only 8.3% with normal Doppler findings in high-risk populations. 2
Research demonstrates that bilateral notching is superior to unilateral notching for minimizing false-positive results, and the combination of elevated RI plus notching is more predictive than either parameter alone. 2
Critical Management Principle
The most important clinical point: While abnormal uterine artery Doppler identifies high-risk pregnancies, it should NOT be used for routine clinical management or to guide delivery timing. 1, 3
Why Uterine Artery Doppler Has Limited Clinical Utility:
The Society for Maternal-Fetal Medicine (SMFM) explicitly recommends against using uterine artery Doppler for routine clinical management of FGR because it does not add clinically valuable information beyond umbilical artery Doppler for guiding delivery timing or improving outcomes. 1, 3
Uterine artery Doppler has limited diagnostic accuracy and lacks standardization for technique, gestational age at testing, and criteria for abnormal results. 1
Uterine artery Doppler assesses the maternal side of placental flow, while umbilical artery Doppler assesses the fetal side—the latter directly determines fetal well-being and delivery timing. 3
Immediate Management Algorithm
If Detected Before 16 Weeks:
- Initiate low-dose aspirin (75-160 mg daily) immediately, taken in the evening to maximize efficacy, as this can prevent small-for-gestational-age infants when started before 16 weeks (ideally) or no later than 20 weeks. 4
Surveillance Protocol Throughout Pregnancy:
Serial Growth Monitoring:
Implement serial fundal height measurements on a customized chart starting at 22-26 weeks, with ultrasound if measurements fall below the 10th percentile or show static/slow growth. 4
Schedule growth ultrasounds every 3-4 weeks starting in the second trimester to detect FGR early. 4
Doppler Surveillance Strategy:
Do NOT continue serial uterine artery Doppler assessments—this does not guide management. 1, 3
If FGR is suspected, immediately switch to umbilical artery Doppler surveillance, as this is the primary vessel with Level I evidence for reducing perinatal mortality. 1, 4
Umbilical artery Doppler in suspected IUGR significantly reduces perinatal deaths (RR 0.71), cesarean deliveries (RR 0.90), and inductions of labor (RR 0.89) without increasing unnecessary interventions. 1
If Preeclampsia Develops:
Perform a one-time comprehensive assessment including fetal biometry, amniotic fluid volume, and both uterine and umbilical artery Doppler to characterize placental dysfunction severity. 4, 3
After initial assessment, serial umbilical artery Doppler every 1-2 weeks guides subsequent management, not continued uterine artery assessment. 4, 3
Delivery Timing Based on Umbilical Artery Doppler (Not Uterine Artery)
Once FGR is diagnosed, delivery timing is determined by umbilical artery Doppler findings:
| Umbilical Artery Doppler Finding | Delivery Timing | Surveillance Frequency |
|---|---|---|
| Normal flow | 38-39 weeks (EFW 3rd-10th percentile) | Every 2 weeks [5] |
| Decreased diastolic flow | 37 weeks | Weekly [5] |
| Absent end-diastolic velocity (AEDV) | 33-34 weeks | 2-3 times per week [5] |
| Reversed end-diastolic velocity (REDV) | 30-32 weeks | Hospitalization with CTG 1-2 times daily [5] |
Common Pitfalls and Caveats
Critical Errors to Avoid:
Do NOT use uterine artery Doppler to guide delivery timing—this is a screening/risk stratification tool only, not a management tool. 1, 3
Do NOT continue serial uterine artery Doppler assessments once FGR is suspected—switch immediately to umbilical artery Doppler. 1, 4
Do NOT rely on middle cerebral artery, ductus venosus, or uterine artery Doppler for routine clinical management of early or late-onset FGR. 1, 5
Do NOT miss the window for aspirin prophylaxis—it must be started before 16 weeks (ideally) to provide benefit. 4
Special Considerations:
In rare cases of severe placental insufficiency, reversed diastolic flow in the uterine artery (not just notching) has been reported and is associated with eclampsia and severe IUGR requiring immediate delivery. 6
Only one-third of preeclamptic women show signs of increased uterine artery vascular impedance in the third trimester, but when present, it is strongly related to adverse outcomes. 7
Research shows that uterine artery notching is present in only 35.2% of severe preeclampsia cases and 25% of all preeclamptic pregnancies in the third trimester, emphasizing that normal uterine artery Doppler does not exclude disease. 7