When is a fetal echocardiogram indicated, how is it performed, and what are the management steps for normal versus abnormal findings?

Fetal Echocardiography: Indications, Technique, and Management

When to Order Fetal Echocardiography

Fetal echocardiography is indicated for any pregnancy with maternal risk factors (family history of congenital heart disease, diabetes, lupus, teratogen exposure) or fetal abnormalities (abnormal screening ultrasound, arrhythmia, increased nuchal translucency ≥3mm, chromosomal abnormalities, or extracardiac anomalies). 1

Class I (Strongest) Indications - Maternal Factors:

• First-degree relative with congenital heart disease (parent, sibling) 1
• Maternal diabetes mellitus (pregestational) 1
• Maternal systemic lupus erythematosus 1
• Teratogen exposure during vulnerable periods (first trimester) 1
• Family history of left or right heart obstructive lesions 1

Class I (Strongest) Indications - Fetal Factors:

• Abnormal-appearing heart on routine obstetric ultrasound 1
• Fetal arrhythmia (tachycardia, bradycardia, or irregular rhythm) 1
• Nuchal translucency ≥3mm or ≥99th percentile 1, 2
• Chromosomal abnormalities 1
• Other fetal system abnormalities when pregnancy management decisions are required 1
• Non-immune hydrops fetalis 1
• Extracardiac anomalies (congenital lung lesions, diaphragmatic hernia) 1, 3
• Multiple gestations (especially monochorionic twins with 9-fold increased risk of congenital heart disease) 1, 3

Common pitfall: The ACC/AHA guidelines emphasize that most congenital heart disease occurs in low-risk pregnancies, so maintaining a low threshold for referral is critical. 1, 4, 5

Timing and Technical Performance

Optimal Timing:

• Standard fetal echocardiography: 18-22 weeks gestation via transabdominal approach 1, 2, 4
• Early echocardiography: 12-14 weeks via transvaginal approach (detects 50-65% of major anomalies but requires repeat at 18-22 weeks) 1, 2
• First trimester screening: 11-14 weeks (limited evaluation, always requires second trimester confirmation) 1, 2

Technical Approach:

The ACC/AHA guidelines specify that complete cardiac evaluation requires: 1

Imaging modalities:

• Two-dimensional echocardiography for segmental cardiac anatomy analysis 1
• Doppler examination for blood flow across cardiac valves, great arteries, ductus arteriosus, and umbilical arteries 1
• M-mode echocardiography for ventricular dimension and function assessment 4, 6
• Color Doppler for hemodynamic evaluation 4, 7

Key structures to evaluate:

• Four-chamber view 7
• Outflow tract views 7
• Cardiac valves and great vessels 1
• Ductus arteriosus patency and flow direction 1
• Ventricular function (fractional shortening >28%, ejection fraction) 3, 6
• Cardiothoracic ratio (normal 0.25-0.35) 3

Important caveat: Doppler studies should be reserved for high-risk fetuses (nuchal translucency ≥3mm) following ALARA principles to minimize fetal exposure. 1, 2

Detection Rates by Timing:

• 11-14 weeks: Detects 50% of hypoplastic left heart and atrioventricular septal defects, <25% of conotruncal abnormalities 1, 2
• 18-22 weeks: Detection rate approaches 80% in experienced centers 1
• Complete evaluation possible at 13-14 weeks in >90% of cases 1

Management Based on Findings

Normal Fetal Echocardiogram:

For high-risk pregnancies with normal findings:

• Provide reassurance to parents 1
• No additional cardiac surveillance required unless new risk factors emerge 1
• Routine obstetric care continues 2

Critical point: Even with early normal echocardiography (11-14 weeks), repeat evaluation at 18-22 weeks is mandatory due to evolving cardiac anatomy and the limitations of early imaging. 1, 2

Abnormal Fetal Echocardiogram:

Immediate multidisciplinary coordination required involving: 1, 3

• Pediatric cardiology
• Maternal-fetal medicine
• Genetics
• Neonatology
• Pediatric cardiac surgery

Management algorithm for abnormal findings:

1. Comprehensive genetic evaluation:

   • Offer invasive diagnostic testing (chorionic villus sampling or amniocentesis) 1
   • Screen for chromosomal abnormalities and genetic syndromes 1
   • Evaluate for extracardiac anomalies 1, 8

2. Serial monitoring protocol:

   • Monthly to bimonthly fetal echocardiography to assess progression 9, 8
   • Monitor for cardiac dilatation, increasing valvular insufficiency, and hydrops 8
   • Use Cardiovascular Profile Score (CVPS) for risk stratification (score <7 indicates increased perinatal death risk) 3
   • Assess Myocardial Performance Index (Tei index) 3, 9

3. Assess for ductal-dependent lesions:

   • Critical for planning prostaglandin E1 administration at delivery 1, 3
   • Prevents catastrophic decompensation when ductus arteriosus closes 1

4. Parental counseling must address: 1

   • Specific cardiac diagnosis and prognosis
   • Surgical options and long-term outcomes
   • Option for pregnancy termination (earlier detection allows safer termination if chosen) 1
   • Delivery planning at tertiary center with immediate cardiac surgical capabilities 3, 9

5. Delivery planning:

   • Mandatory delivery at tertiary center with maternal-fetal medicine, pediatric cardiology, cardiac surgery, and NICU capabilities 3, 9
   • Coordinate timing to optimize neonatal intervention 5
   • Prepare for immediate postnatal management (prostaglandin infusion, mechanical ventilation, inotropic support) 3

6. Consider fetal intervention for:

   • Arrhythmias amenable to transplacental therapy 1
   • Significant or intermittent arrhythmias requiring treatment 1

Critical management point: The ACC/AHA emphasizes that early recognition allows opportunity for transplacental therapy in arrhythmias and improved postnatal outcomes through coordinated delivery planning. 1

Special Considerations for Specific Findings:

Increased nuchal translucency (≥3mm) with normal cardiac anatomy:

• Repeat fetal echocardiography in second trimester is mandatory 1, 2
• Risk of congenital heart disease remains elevated even with initially normal findings 1
• Consider ductus venosus Doppler (reversed a-wave increases cardiac risk 3-fold) 1

Multiple gestations (especially monochorionic twins):

• 9-fold increased risk of congenital heart disease (14-fold in twin-twin transfusion syndrome) 3
• Monitor for recipient twin cardiomyopathy and altered ductal flow 3
• Assess for Twin Reversed Arterial Perfusion (TRAP) sequence 1, 3

Gestational diabetes:

• Increased interventricular septum and ventricular wall thickness common but not associated with structural defects 6
• Altered diastolic function parameters expected 6