What is the management of fetal bradycardia?

Management of Fetal Bradycardia

Fetal bradycardia requires immediate intervention with maternal position change to left lateral decubitus, oxygen administration, and correction of any underlying causes, with emergency delivery if bradycardia persists beyond 10 minutes due to increased risk of hypoxic-ischemic injury. 1, 2

Initial Assessment and Immediate Interventions

1. First-line interventions (implement immediately):

   • Change maternal position to left lateral decubitus to relieve aortocaval compression 1
   • Administer supplemental oxygen to mother
   • Assess for and correct maternal hypotension 1
   • Discontinue any uterotonic agents if being administered 1
   • Rule out acute intrapartum accidents (placental abruption, umbilical cord prolapse, uterine rupture) 2

2. If bradycardia persists (after initial interventions):

   • For uterine hypertonus/hyperstimulation: consider acute tocolysis (terbutaline) 3, 2
   • Continue preparation for emergency delivery while awaiting recovery 3
   • Monitor fetal heart rate continuously

Time-Critical Decision Making

• If bradycardia persists <10 minutes: Continue conservative measures with close monitoring
• If bradycardia persists >10 minutes: Consider emergency delivery (cesarean section) as this becomes "terminal bradycardia" with increased risk of hypoxic-ischemic injury to deep gray matter of the brain 2, 1

Diagnostic Evaluation (for persistent or recurrent bradycardia)

• Perform detailed ultrasound including fetal echocardiogram to evaluate for:

  • Structural cardiac abnormalities
  • Congenital heart block
  • Other anatomical abnormalities 1

• Laboratory testing:

  • Maternal autoimmune disease screening (anti-Ro/SSA and anti-La/SSB antibodies) 1, 4
  • Fetal karyotype and/or chromosomal microarray analysis if structural abnormalities are present 1
  • MCA Doppler to assess for fetal anemia 1

Management Based on Etiology

Congenital Complete Heart Block

• Most common cause of persistent fetal bradycardia 4
• For isolated congenital heart block with narrow QRS complex: close monitoring is generally recommended 1
• For immune-mediated heart block (anti-Ro/SSA antibodies): corticosteroid therapy has not shown benefit once third-degree AV block has developed 1

Blocked Atrial Extrasystoles

• Can present as bradycardia, even in first trimester 5
• May evolve into supraventricular tachycardia and hydrops fetalis
• Requires weekly heart rate assessment 5

Maternal Conditions

• Urosepsis: Fetal bradycardia may be due to endotoxin release from gram-negative bacteria rather than maternal hypothermia alone 6
• Maternal beta-blocker use: Monitor fetal heart rate during uptitration, especially when doses exceed 800 mg/24h 1

Special Considerations

• For women with complete heart block and symptoms, consider temporary pacing during delivery 1
• Avoid atenolol in pregnancy due to risk of fetal growth restriction 1
• In-utero therapy for bradyarrhythmia with hydrops is considered investigational 1

Pitfalls and Caveats

• Do not delay emergency delivery if acute intrapartum accidents are suspected (placental abruption, cord prolapse, uterine rupture) 2
• Tocolysis should be regarded as a temporary measure until fetal heart rate recovery is apparent 3
• Fetal bradycardia due to maternal beta-blocker administration requires careful monitoring 1
• First trimester bradycardia should be differentiated between atrial extrasystoles, sinus bradycardia, and those associated with major structural cardiac abnormalities (which have high fetal loss rate) 5