What is the recommended management for a fetus with a prenatal diagnosis of Tetralogy of Fallot (TOF) with pulmonary stenosis?

Prenatal Management of Tetralogy of Fallot with Pulmonary Stenosis

A fetus diagnosed with Tetralogy of Fallot (TOF) with pulmonary stenosis requires genetic screening for 22q11.2 deletion, serial fetal echocardiography every 2-4 weeks to assess pulmonary valve and artery size, and planned delivery at a tertiary cardiac center with immediate access to pediatric cardiac surgery. 1

Immediate Prenatal Actions

Genetic Evaluation

• Offer screening for 22q11.2 deletion syndrome to all pregnant women with fetuses diagnosed with TOF, as this conotruncal abnormality carries an 18% risk of 22q11 deletion 1, 2, 3
• Arrange genetic consultation if 22q11.2 deletion or other genetic syndrome is identified, as this increases recurrence risk in future pregnancies to 50% (versus 4-6% without deletion) 1
• Screen for additional extracardiac anomalies, which occur in 46% of cases 3

Fetal Echocardiographic Surveillance Protocol

• Perform fetal echocardiography every 2-4 weeks by specialists with expertise in congenital heart disease to monitor cardiac progression and predict neonatal outcomes 1
• Measure and document z-scores for:
  • Pulmonary valve (PV) diameter: A PV z-score ≤-5 predicts ductal dependence with 78% sensitivity and 87% specificity 4
  • Main pulmonary artery (MPA) diameter: Lower MPA z-scores correlate with need for neonatal intervention 4
  • Branch pulmonary artery size and confluence: Presence of confluent pulmonary arteries and MPA predict likelihood of complete repair in the first year of life 3
• Assess ductus arteriosus flow direction: Reversed left-to-right flow across the ductus arteriosus increases odds of ductal dependence 25-fold 4

Critical Predictors of Neonatal Intervention

High-Risk Features Requiring Prostaglandin at Birth

• Fetal PV z-score <-3 (100% sensitivity for ductal dependence) 4
• Any left-to-right flow at the level of the ductus arteriosus 4
• Fetal PV z-score <-5 (78% sensitivity, 87% specificity for ductal dependence) 4
• MPA z-score <-3.94 4

Fetuses meeting these criteria must deliver at centers where prostaglandin E1 is immediately available, as approximately 23% (10 of 44) of TOF patients with antegrade pulmonary blood flow will be ductal dependent 4

Delivery Planning

Location and Team

• Plan delivery at a tertiary care center with on-site pediatric cardiac surgery capability 1
• Coordinate multidisciplinary team including maternal-fetal medicine specialists, pediatric cardiologists, cardiac surgeons, and neonatologists 1
• Cesarean delivery is not indicated based solely on cardiac diagnosis; follow standard obstetric indications 1

Timing

• Administer corticosteroids for fetal lung maturation at 24-33 6/7 weeks if preterm delivery is anticipated 1
• Standard term delivery is appropriate unless other obstetric or fetal indications exist 1

Parental Counseling Framework

Surgical Expectations

• Inform parents that full surgical repair within the first year of life is the mainstay of therapy, either as primary repair or after palliative shunt procedure 2, 5
• Explain that 42% of infants undergoing staged repair achieve pulmonary valve-sparing repair (PVSR), which preserves long-term right ventricular function 6
• Discuss that 5 and 10-year survival rates are 93%, with freedom from reoperation at 87% (5 years) and 82% (10 years) for staged repairs 6

Genetic and Recurrence Risks

• Without 22q11 deletion: 4-6% recurrence risk in future pregnancies 1
• With 22q11 deletion: 50% recurrence risk 1
• Offer fetal echocardiography in all future pregnancies 1

Associated Anomalies

• Abnormal karyotype occurs in 11% of cases 3
• Extracardiac anomalies present in 46% 3
• 22q11 deletion found in 18% 3

Postnatal Management Pathway

Immediate Assessment

• Evaluate oxygenation status and confirm diagnosis with postnatal echocardiography 1
• Assess pulmonary artery anatomy and source of pulmonary blood flow 1
• Initiate prostaglandin E1 if ductal dependent (predicted by fetal PV z-score <-3 or reversed ductal flow) 4

Surgical Strategy

• Timing of repair depends on degree of right ventricular outflow tract obstruction and clinical status 5
• Symptomatic neonates requiring early intervention may undergo staged approach with initial systemic-to-pulmonary artery shunt, allowing pulmonary artery growth before complete repair 6
• Complete repair aims to relieve RVOT obstruction via transannular patch or valve-sparing techniques 5

Critical Pitfalls to Avoid

• Do not deliver at centers without immediate prostaglandin availability if fetal PV z-score is <-3 or any left-to-right ductal flow is present 4
• Do not assume prenatal diagnosis of major aortopulmonary collateral arteries is reliable (incorrectly described in 13% of cases); postnatal imaging is essential 3
• Do not overlook the 34% pregnancy termination rate in historical cohorts due to associated anomalies; comprehensive counseling about modern surgical outcomes is critical 3
• Recognize that TOF is a lifelong disease requiring careful follow-up through adulthood with potential for additional surgical and interventional procedures 2