When is Doppler ultrasound indicated in pregnancy and how should abnormal Doppler findings be managed?

Doppler Ultrasound in Pregnancy: Indications and Management

Primary Indication

Umbilical artery Doppler is indicated for surveillance of pregnancies with suspected intrauterine growth restriction (IUGR), where it reduces perinatal mortality by 29% and should be initiated immediately upon diagnosis. 1

When to Initiate Doppler Surveillance

Specific Clinical Scenarios Requiring Doppler

• Suspected IUGR: Begin weekly umbilical artery Doppler when estimated fetal weight falls below the 10th percentile for gestational age 1, 2
• Preeclampsia with fetal concerns: Perform Doppler at initial diagnosis of preeclampsia, then serially from 26 weeks until delivery if IUGR is confirmed 1
• Prior pregnancy with severe IUGR: Initiate surveillance at 26-28 weeks with serial growth ultrasounds every 3-4 weeks plus weekly Doppler once IUGR is suspected 2
• Abnormal biophysical profile in preterm pregnancy: Use Doppler to differentiate hypoxic growth-restricted fetuses from constitutionally small but healthy fetuses 1

When NOT to Use Doppler

• Routine screening in low-risk pregnancies: Doppler has no value as a screening tool in healthy pregnancies and should not be used 1, 3
• Prediction of IUGR before it develops: Standards are lacking for technique, gestational age, and abnormal criteria when used predictively 1, 2

Surveillance Protocol Based on Doppler Findings

Normal Umbilical Artery Doppler

• Continue weekly Doppler surveillance 1
• Add weekly cardiotocography (NST or biophysical profile) after viability 1, 2
• Plan delivery at 38-39 weeks if estimated fetal weight remains 3rd-10th percentile 1, 2

Decreased End-Diastolic Flow (Elevated Resistance Indices >95th Percentile)

• Increase to weekly Doppler assessments 1, 2
• Increase cardiotocography frequency as clinically indicated 1, 2
• Plan delivery at 37 weeks gestation 1, 2

Absent End-Diastolic Flow (AEDV)

• Immediately administer antenatal corticosteroids if <34 weeks 1, 2
• Increase Doppler to 2-3 times per week 1
• Perform cardiotocography twice weekly or more often 1, 2
• Daily cardiotocograph monitoring is recommended by some guidelines 1
• Plan delivery at 33-34 weeks gestation 1, 2
• Administer magnesium sulfate for neuroprotection if delivery planned <32 weeks 1, 2

Reversed End-Diastolic Flow (REDV)

• Hospitalize immediately 1, 4
• Administer antenatal corticosteroids if <34 weeks 1, 4
• Perform cardiotocography 1-2 times daily 1, 4
• Increase Doppler to 3 times per week 1, 4
• Daily consultant involvement is mandatory 1, 4
• Plan delivery at 30-32 weeks gestation 1, 4
• Administer magnesium sulfate for neuroprotection if <32 weeks 1, 4

Management Algorithm for Abnormal Doppler

Preterm (<34 weeks) with AEDV or REDV

1. Admit to hospital (for REDV) 1, 4
2. Administer betamethasone 12 mg IM, repeat in 24 hours 1, 2
3. Close observation for 48-72 hours after corticosteroid administration 1
4. Magnesium sulfate 4-6 g IV loading dose if delivery anticipated <32 weeks 1, 2
5. Intensify surveillance: Daily to twice-daily cardiotocography 1, 4
6. Serial Doppler: 2-3 times weekly 1

Term (≥37 weeks) with Any Abnormal Doppler

• Proceed to delivery regardless of Doppler severity 1
• Abnormal umbilical artery Doppler at term is an indication for delivery 1

Mode of Delivery Considerations

Cesarean delivery should be strongly considered for AEDV or REDV due to severe placental insufficiency and high risk of intrapartum fetal compromise 1, 2, 4

• Studies show 75-95% of IUGR pregnancies with AEDV/REDV require cesarean for intrapartum heart rate abnormalities, even when antepartum testing was reassuring 2
• Induction may be reasonable only when resistance indices are elevated but end-diastolic flow remains present, with mandatory continuous fetal monitoring throughout labor 2

Vessels to Interrogate

Umbilical Artery (Primary Vessel)

The umbilical artery is the preferred and only vessel with Level I evidence showing mortality reduction in IUGR management 1, 2

Other Vessels (Not Routinely Recommended)

• Middle cerebral artery: Identifies brain-sparing but has not been evaluated in randomized trials; no specific interventions proven to improve outcomes based on abnormal findings 1, 2
• Ductus venosus: Absent or reversed A-wave predicts stillbirth with 100% sensitivity but routine use not recommended for standard management 1, 2
• Uterine artery: May help refine diagnosis of IUGR but not recommended for routine surveillance 1, 2

Critical Pitfalls to Avoid

Do Not Rely on Normal Fetal Heart Rate Testing Alone

Normal cardiotocography does NOT exclude IUGR progression and should never be the sole surveillance method in high-risk pregnancies 2

• Early/compensated IUGR maintains normal heart rate patterns while Doppler already shows vascular changes 2
• Heart rate abnormalities appear late in the deterioration sequence, after significant Doppler changes 2
• Doppler abnormalities progress predictably: increased umbilical artery resistance → AEDV → REDV → venous Doppler changes → finally abnormal heart rate patterns 1, 2

Distinguish Between AEDV and REDV

Failing to differentiate between absent (delivery at 33-34 weeks) and reversed (delivery at 30-32 weeks) end-diastolic flow leads to inappropriate timing of delivery 1, 4

Ensure Expert Interpretation

Inaccurate Doppler interpretation can lead to inappropriate clinical decisions; measurements must be undertaken by expert operators using duplex mode with pulsed Doppler and color flow mapping 3

Post-Delivery Management

• Obtain cord arterial and venous pH for all growth-restricted infants 1, 2
• Send placenta for histopathologic examination to understand underlying causes and guide future pregnancy management 1, 2