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Fetal Echocardiography Indications

Learning Objectives

Core Knowledge & Clinical Reasoning

  • [ ] Identify maternal, fetal, and familial indications for fetal echocardiography
  • [ ] Recognize which prenatal findings warrant cardiology referral
  • [ ] Understand the optimal timing for fetal echo (18-24 weeks)

Communication & Counseling

  • [ ] Counsel expectant parents on what fetal echo can and cannot detect
  • [ ] Explain the rationale for fetal echo referral without causing undue anxiety

Systems-Based Practice

  • [ ] Coordinate appropriate referrals from OB to pediatric cardiology
  • [ ] Understand the difference between screening obstetric ultrasound and fetal echocardiography

Key Concept

Fetal echo is NOT routine screening It's a specialized diagnostic study performed by pediatric cardiologists for specific indications

When to Refer for Fetal Echo

Maternal Indications

Indication Rationale CHD Risk
Pregestational diabetes Increased CHD risk 3-5%
Phenylketonuria (PKU) Teratogenic if uncontrolled 10-15%
Autoimmune disease (anti-Ro/La+) Risk of heart block 2-5%
Rubella infection Teratogenic Variable
Teratogen exposure Lithium, anticonvulsants, retinoic acid Variable
Assisted reproduction (IVF) Modest increased risk 1.5-2x baseline

Fetal Indications

Finding on OB Ultrasound Action
Suspected cardiac anomaly Urgent fetal echo
Abnormal 4-chamber view Fetal echo
Abnormal outflow tracts Fetal echo
Arrhythmia Fetal echo + possible treatment
Extracardiac anomaly Fetal echo (CHD association)
Increased nuchal translucency (>3.5mm) Fetal echo
Hydrops fetalis Urgent fetal echo
Single umbilical artery Consider fetal echo
Chromosomal abnormality Fetal echo

Familial Indications

Family History CHD Risk Recommendation
CHD in 1st degree relative 3-5% Fetal echo
CHD in 2 or more relatives Higher Fetal echo
Inherited syndrome (Marfan, Noonan, 22q11) Variable Fetal echo
Channelopathy (LQTS) N/A for structure Consider if arrhythmia
Cardiomyopathy Variable Case-by-case

Optimal Timing

Gestational Age Use Case
18-24 weeks Standard timing (optimal visualization)
16-18 weeks Early echo if high suspicion
After 24 weeks May be limited by fetal position, ribs
Serial exams Progressive lesions (tumors, cardiomyopathy)

What Fetal Echo CAN Detect

  • Major structural heart defects (HLHS, TGA, TOF, AVSD)
  • Arrhythmias (SVT, heart block)
  • Cardiac tumors
  • Cardiomyopathy
  • Pericardial effusion

What Fetal Echo May MISS

Lesion Why Difficult
Small VSDs May be too small to visualize
Mild coarctation Isthmus normally small in fetus
Secundum ASD Foramen ovale is normally open
Mild valve stenosis May progress postnatally
TAPVR Pulmonary veins difficult to image

Fetal Arrhythmias

Common Findings

Arrhythmia Significance
Isolated PACs Usually benign, resolve
Sustained SVT May need treatment (maternal digoxin, flecainide)
Complete heart block Often maternal anti-Ro/La; may need pacing at birth
Bradycardia Evaluate for block vs distress

When to Treat In Utero

  • SVT with hydrops or ventricular dysfunction
  • Sustained SVT >200 bpm
  • Complete heart block with hydrops (pacing not possible in utero, but steroids may help)

Board Pearls

Pearl: Pregestational diabetes = fetal echo indication

3-5% CHD risk; gestational diabetes is NOT an indication

Pearl: Increased nuchal translucency >3.5mm = fetal echo

Even with normal karyotype, CHD risk elevated

Pearl: Optimal timing is 18-24 weeks

Earlier imaging possible but visualization limited

Pearl: Normal fetal echo doesn't rule out all CHD

Small VSDs, mild coarctation, ASDs may be missed

Self-Assessment

Q1: A 28-year-old G1P0 with type 1 diabetes (HbA1c 8.5% in first trimester) asks if she needs any special heart testing for the baby. What do you recommend?

Answer **Answer**: Fetal echocardiography at 18-24 weeks **Rationale**: Pregestational diabetes (type 1 or type 2) is an indication for fetal echo due to 3-5% CHD risk. Poor glycemic control (elevated HbA1c) increases risk further. Note: Gestational diabetes diagnosed later in pregnancy is NOT an indication.

Q2: A fetus at 20 weeks has increased nuchal translucency of 4.0mm but normal chromosomes on amniocentesis. Is fetal echo indicated?

Answer **Answer**: Yes - fetal echocardiography is indicated **Rationale**: Increased nuchal translucency (>3.5mm) is associated with CHD even when karyotype is normal. The CHD risk remains elevated (~5-7%) and warrants fetal cardiac evaluation.

Q3: A pregnant woman with SLE and positive anti-Ro antibodies is at 16 weeks. What cardiac monitoring is needed?

Answer **Answer**: Serial fetal echocardiography starting at 16-18 weeks, weekly or biweekly through 26-28 weeks **Rationale**: Anti-Ro/La antibodies cross the placenta and can cause fetal heart block, typically developing between 18-24 weeks. Early and serial monitoring allows detection of first-degree block before it progresses to complete block. If complete block develops, steroids may be considered though efficacy is debated.

Key Guidelines

2014 AHA Scientific Statement: Diagnosis and Treatment of Fetal Cardiac Disease Circulation. 2014;129:2183-2242 PMID: 24763516

2020 AIUM Practice Parameter for the Performance of Fetal Echocardiography J Ultrasound Med. 2020;39:E5-E16 PMID: 32583449

References

  • Donofrio MT, et al. Circulation. 2014;129:2183-2242 (AHA Scientific Statement)
  • AIUM Practice Parameter for Fetal Echocardiography. 2020
  • Friedberg MK, et al. Circulation. 2009;119:e21-e24