What is the management of fetal bradycardia?

Management of Fetal Bradycardia

Fetal bradycardia requires immediate assessment and intervention based on the underlying cause, with emergency delivery indicated for persistent bradycardia that increases risk of hypoxic-ischemic injury. 1

Immediate Management Steps

1. Change maternal position to left lateral decubitus to relieve potential aortocaval compression 1
2. Assess for and correct maternal hypotension 1
3. Discontinue any uterotonic agents if being administered 1
4. Perform detailed ultrasound evaluation, including fetal echocardiogram to evaluate for:
   • Structural cardiac abnormalities
   • Congenital heart block
   • Other anatomical abnormalities 1

Diagnostic Workup

• Maternal autoimmune disease screening (anti-Ro/SSA and anti-La/SSB antibodies) for persistent bradycardia 1
• Fetal karyotype and/or chromosomal microarray analysis, particularly if structural abnormalities are present 1
• Middle cerebral artery (MCA) Doppler to assess for fetal anemia 1
• Echocardiography to determine underlying mechanism of bradycardia 2

Management Based on Etiology

1. Congenital Complete Heart Block

• Most common cause of persistent fetal bradycardia 3
• For immune-mediated heart block (positive anti-Ro/SSA antibodies):
  • Corticosteroid therapy has not shown benefit once third-degree AV block has developed 1
  • Close monitoring for development of hydrops fetalis 3
• For isolated congenital heart block with narrow QRS complex:
  • Close monitoring is generally recommended 1
  • Favorable prognosis without immediate pacemaker implantation 3
• For congenital heart block with structural heart disease:
  • Higher mortality risk, especially with isomerism 2
  • More aggressive monitoring and earlier intervention may be needed 2

2. Blocked Atrial Bigeminy

• Generally has excellent outcome 2
• Monitor for potential development of post-natal tachyarrhythmias 2

3. Sinus Bradycardia

• May be associated with serious underlying conditions 2
• Requires comprehensive evaluation 2
• Not necessarily an indication for urgent delivery if fetal well-being can be confirmed 4

4. Acute Bradycardia During Labor

• May be vagal in origin (head compression, cord compression) 5
• Assess severity and duration rather than presuming etiology 5
• Consider atropine administration in otherwise healthy fetus with acute bradycardia 5

Delivery Considerations

• Emergency delivery (cesarean section) if bradycardia persists and increases risk of hypoxic-ischemic injury 1
• For women with complete heart block and symptoms, consider temporary pacing during delivery 1
• Timing of delivery should be based on:
  • Presence of hydrops fetalis
  • Ventricular dysfunction
  • Gestational age
  • Response to interventions 2

Post-Delivery Management

• Regular assessment of cardiac function for infants with congenital heart block 1
• Pacemaker implantation may be required in approximately 58% of atrioventricular blocks within 18 months of follow-up 2
• Single-chamber pacing initially, with consideration of epicardial approach in small infants 1

Medication Considerations

• Avoid atenolol in pregnancy due to risk of fetal growth restriction 1
• Monitor fetal heart rate during uptitration of labetalol, especially when doses exceed 800 mg/24h 1
• In-utero therapy for bradyarrhythmia with hydrops is considered investigational 1

Pitfalls and Caveats

• Distinguishing between different causes of fetal bradycardia is crucial as management differs significantly
• Not all persistent bradycardias require emergency delivery - confirmation of fetal well-being through appropriate testing can avoid unnecessary interventions 4
• Risk factors for mortality in fetal bradycardia include congenital heart disease, hydrops and/or ventricular dysfunction 2
• Management strategies for immune-mediated heart block remain controversial, with variable practices across centers 2