Fetal Echocardiography
A Practical Sonography + MFM Workflow
Comprehensive Guide to Indications, Technique, and Interpretation
Why Fetal Echocardiography Matters
- Congenital heart disease affects 0.8–1% of live births
- Prenatal detection enables delivery planning at specialized centers
- Improves neonatal outcomes for critical ductal-dependent lesions
- Reduces morbidity and mortality through coordinated care
- Allows for parental counseling and informed decision-making
Clinician Pearl: Every hour saved in postnatal diagnosis of critical CHD can prevent irreversible shock and end-organ damage.
Indications for Fetal Echocardiography
- Maternal: Pre-gestational diabetes, phenylketonuria, lupus with anti-Ro/La
- Fetal: Suspected cardiac anomaly on screening, extracardiac anomalies, arrhythmia, hydrops
- Familial: Previous child with CHD, first-degree relative with CHD, genetic syndromes
- Exposures: Teratogens (lithium, valproic acid, retinoic acid), IVF with ICSI
Pitfall: Normal anatomy scan does NOT rule out CHD. Four-chamber view alone misses 40% of significant cardiac lesions.
Timing of Fetal Echocardiography
- Standard timing: 18–22 weeks (optimal cardiac visualization)
- Early echo (13–16 weeks): Monochorionic twins, prior child with CHD, genetic syndromes
- Late echo (>28 weeks): Evolving lesions (aortic stenosis, TOF), arrhythmias, function assessment
- Repeat scanning: Consider if initial suboptimal views, maternal condition changes, or fetal growth concerns
Clinician Pearl: Conotruncal anomalies may not be fully apparent until mid-second trimester. Schedule accordingly.
Machine Optimization & Doppler Safety
- Use highest frequency transducer with adequate penetration (5–7 MHz)
- Optimize B-mode first: gain, focus, depth, frame rate
- Color Doppler: reduce box size, lower velocity scale (20–30 cm/s)
- ALARA principle: Thermal Index (TI) < 1.0, minimize spectral Doppler duration
- Avoid prolonged Doppler in first trimester
Pitfall: Excessive Doppler power or prolonged insonation can cause tissue heating. Use brief, targeted bursts only.
Sequential Segmental Analysis Framework
- Step 1: Determine atrial situs (systemic/pulmonary veins, stomach position)
- Step 2: Define atrioventricular connections (which atrium to which ventricle)
- Step 3: Assess ventriculoarterial connections (which ventricle to which great vessel)
- Step 4: Identify associated anomalies (septal defects, valve abnormalities, arch)
- Describe what IS present, not just what's "normal"
Clinician Pearl: Segmental analysis is critical for complex CHD. Describe anatomy systematically, avoid premature diagnostic labels.
Cardiac Axis Assessment
- Normal: 45° ± 20° to the left of midline
- Assess in transverse four-chamber view
- Abnormal axis may indicate heterotaxy, diaphragmatic hernia, or cardiac malposition
Midline
45° axis
Heart
Left
Right
Clinician Pearl: Use stomach position as anatomical left marker. Cardiac apex should point toward stomach.
Four-Chamber View: The Foundation
- Check: Size equality (1:1 ratio), intact ventricular septum, offset AV valves
- Foramen ovale with visible flap, pericardium without effusion
- Moderator band in RV, smooth LA wall confirms chamber identity
Pitfall: Oblique imaging plane can falsely suggest VSD. Confirm in multiple planes before reporting septal defect.
Outflow Tract Views: LVOT & RVOT
- LVOT: Aorta arises from LV, mitral-aortic continuity, no VSD
- RVOT: Pulmonary artery from RV, crosses anterior to aorta, bifurcates
- Normal: outflows cross at ~60° angle
- Parallel outflows suggest transposition or double outlet ventricle
LV
RV
Ao
PA
✕
Normal crossing
Clinician Pearl: If outflows appear parallel, suspect D-TGA or DORV. Always confirm great artery relationships.
Three-Vessel View (3VV) & Tracheal View (3VT)
- 3VV: PA, Ao, SVC in transverse plane—similar size, aligned, V-shaped confluence
- 3VT: Adds trachea (to right of vessels), confirms sidedness
- Abnormal 3VV: size discrepancy, absent/abnormal vessel, abnormal confluence
- Detects coarctation, arch anomalies, vascular rings
PA
Ao
SVC
T
V-shaped confluence
Left
Right
Clinician Pearl: In 3VT, trachea should be rightmost structure. If leftward, suspect right aortic arch.
Aortic and Ductal Arch Views
- Aortic arch: "Candy cane" shape, three head-neck vessels, left-sided (usually)
- Ductal arch: "Hockey stick" shape, ductus arteriosus connects PA to descending aorta
- Assess arch sidedness, branching pattern, isthmus diameter
- Coarctation signs: small isthmus, posterior shelf, discrepant flow
Pitfall: Right aortic arch occurs in 25% of TOF. Always check arch sidedness and branching.
Doppler Echocardiography: Key Concepts
- Color Doppler: Confirms flow direction, identifies turbulence, detects regurgitation
- Pulsed-wave Doppler: Measures velocities across valves, ducts, arches
- Normal findings: Antegrade flow in outflows, low-velocity AV inflow, ductal right-to-left shunt
- Abnormal patterns: Retrograde diastolic flow (aortic regurg, coarct), monophasic umbilical vein
- Assess for hydrops: TR jet velocity > 80 cm/s may indicate CHF
Clinician Pearl: High-velocity tricuspid regurgitation suggests elevated RV pressure—look for pulmonic stenosis or hypoplasia.
Assessing Cardiac Function & Hydrops
- Qualitative assessment: ventricular contractility, AV valve regurgitation, ejection
- Signs of heart failure: Cardiomegaly (>1/3 thoracic diameter), pericardial effusion, ascites, pleural effusion, scalp edema
- Diastolic dysfunction: monophasic venous Doppler, reversed A-wave in ductus venosus
- Arrhythmia-induced failure: sustained tachycardia or bradycardia
Pitfall: Hydrops has many etiologies. Always assess for anemia, infection, and structural heart disease concurrently.
Algorithm: Indications → Referral Pathway
Patient with Indication (maternal, fetal, familial)
High-risk or abnormal screening?
YES → Direct fetal echo referral at 18–22 weeks
NO → Standard anatomy scan, consider fetal echo if findings emerge
Coordinate with MFM & pediatric cardiology
Clinician Pearl: Early referral allows for optimal timing. Don't delay—cardiac structures evolve quickly.
Algorithm: Abnormal Finding → Triage
Abnormal screening view or suspected CHD
Critical vs. non-critical?
CRITICAL: Suspected HLHS, TGA, TAPVR → Same-day MFM consult
NON-CRITICAL: VSD, mild AS → Schedule fetal echo within 1–2 weeks
Confirm anatomy, discuss prognosis, plan delivery at tertiary center
Pitfall: Delaying referral for critical CHD can result in unplanned delivery without cardiac surgery backup.
Red Flags on Screening Ultrasound
- Asymmetric ventricles (>1.2:1 ratio) or single-appearing ventricle
- Abnormal cardiac axis (<25° or >65°)
- Pericardial effusion, cardiomegaly, hydrops
- Absent or abnormal three-vessel view
- Arrhythmia: sustained bradycardia (<110 bpm), tachycardia (>180 bpm), irregular rhythm
- Extracardiac anomalies (increases CHD risk 5–10×)
Clinician Pearl: When in doubt, refer. Sonographers should have low threshold for requesting MFM or pediatric cardiology input.
Common Congenital Heart Defects: Patterns
- Left heart obstructive: HLHS, critical AS, coarctation, interrupted aortic arch
- Right heart obstructive: Pulmonic stenosis, pulmonary atresia, Ebstein anomaly, TOF
- Mixing lesions: D-TGA, TAPVR, truncus arteriosus, single ventricle
- Septal defects: VSD (most common), ASD, AVSD (associated with trisomy 21)
- Valve abnormalities: Tricuspid or mitral regurgitation, dysplastic valves
Pitfall: Isolated small VSD often closes spontaneously. Avoid over-alarming families—counsel on natural history.
Algorithm: Fetal Arrhythmia Evaluation
Irregular or abnormal heart rate detected
M-mode or Doppler: Bradycardia, tachycardia, or irregular?
BRADYCARDIA (<110 bpm): Check for heart block, assess for anti-Ro/La, rule out CHD
TACHYCARDIA (>180 bpm): SVT vs. atrial flutter—assess A:V ratio, check for hydrops
IRREGULAR: PACs (benign) vs. bigeminy—document frequency
Serial monitoring, consider fetal treatment (digoxin, flecainide), plan delivery
Clinician Pearl: Isolated PACs are benign and very common. Reassure parents—most resolve spontaneously.
Case Vignette: Hypoplastic Left Heart
Clinical Scenario
Patient: 21-week fetus, maternal age 32, no risk factors.
Findings: Small left ventricle (3 mm vs. RV 12 mm), hypoplastic ascending aorta (2 mm), mitral atresia, retrograde flow in aortic arch, large RV with tricuspid regurgitation.
Diagnosis: Hypoplastic left heart syndrome (HLHS).
Next Steps: Confirm diagnosis with pediatric cardiology. Counsel on three-stage surgical palliation (Norwood, Glenn, Fontan) vs. transplant vs. comfort care. Plan delivery at tertiary center with immediate PGE1 infusion. Serial growth and Doppler assessment. Genetic testing offered.
Clinician Pearl: HLHS is ductal-dependent. Delivery must occur at center with cardiac surgery—any delay risks cardiovascular collapse.
Case Vignette: Fetal Supraventricular Tachycardia
Clinical Scenario
Patient: 28-week fetus, referred for irregular heart rate on screening.
Findings: Heart rate 240 bpm, sustained, 1:1 A:V conduction on M-mode. Moderate tricuspid regurgitation, small pericardial effusion (3 mm), no ascites. Structurally normal heart.
Diagnosis: Fetal supraventricular tachycardia (SVT) with early hydrops.
Next Steps: Urgent MFM consultation. Consider transplacental antiarrhythmic therapy (digoxin vs. flecainide). Serial monitoring for resolution or worsening hydrops. Pediatric cardiology at delivery for rhythm management and possible cardioversion.
Pitfall: SVT causing hydrops requires urgent treatment. Delayed therapy can lead to fetal demise or severe cardiac dysfunction.
Fetal Echocardiography Reporting Checklist
Fetal position, gestational age, indication
Cardiac axis and position
Situs (atrial, visceral)
Four-chamber view (size, septum, AV valves)
Outflow tracts (LVOT, RVOT, crossing)
Three-vessel and tracheal views
Aortic and ductal arches
Systemic and pulmonary venous return
Doppler assessment (color, spectral)
Cardiac function, effusion, hydrops
Rhythm assessment (rate, regularity)
Limitations and recommendations
Clinician Pearl: Document image quality and limitations. If suboptimal, state explicitly and recommend repeat study.
Limitations of Fetal Echocardiography
- Detection rate ~60–80% for major CHD (operator- and setting-dependent)
- Small defects (e.g., small VSD, ASD) may be missed
- Some lesions evolve: coarctation, AS may worsen; others improve
- Fetal circulation differs: patent ductus and foramen ovale alter flow patterns
- Postnatal confirmation: All suspected CHD requires neonatal echocardiography
- False positives occur—balance sensitivity with parental anxiety
Pitfall: Normal fetal echo does NOT guarantee normal postnatal heart. Counsel families on need for newborn cardiac evaluation.
Counseling & Multidisciplinary Planning
- Provide clear, empathetic explanation of findings and prognosis
- Involve pediatric cardiology early for co-counseling
- Discuss delivery location: must have pediatric cardiac surgery for critical CHD
- Offer genetic testing (microarray, exome) if syndromic features or complex CHD
- Address parental concerns: natural history, surgical options, long-term outcomes
- Support decision-making: continuation vs. termination (where legal)
Clinician Pearl: Multidisciplinary team approach improves outcomes and family satisfaction. Include neonatology, genetics, and social work.
Summary: Key Take-Home Points
- Systematic fetal echocardiography improves CHD detection and outcomes
- Follow segmental analysis: situs → connections → relationships
- Standard views (4CH, LVOT, RVOT, 3VV, arches) are essential—never skip
- Red flags on screening: asymmetric ventricles, abnormal axis, arrhythmia
- Use Doppler judiciously: ALARA principle, minimize duration
- Coordinate care: MFM, pediatric cardiology, neonatology, genetics
- Postnatal echo is mandatory—fetal findings evolve
Clinician Pearl: A reproducible, systematic approach to fetal echocardiography saves lives. Practice makes proficient.