Is propranolol (beta blocker) safe to use during pregnancy?

Propranolol Use During Pregnancy

Propranolol can be used during pregnancy when clinically necessary, but should be avoided in the first trimester if possible, used at the lowest effective dose, and requires close monitoring for intrauterine growth retardation. 1, 2

Safety Classification and Positioning

• Propranolol is FDA Pregnancy Category C, meaning animal studies show adverse effects but human data is limited 3
• The American Heart Association considers propranolol a relatively safe first-line agent for chronic prophylaxis during pregnancy, with a longer safety record compared to other beta-blockers 1, 2
• For acute conversion of paroxysmal supraventricular tachycardia, propranolol receives a Class IIa recommendation (reasonable to use), while for prophylactic therapy it also receives Class IIa recommendation 4

Timing Considerations: First Trimester Avoidance

• Beta-blockers including propranolol should be avoided during the first trimester when possible, as this is when the risk of congenital malformations and growth retardation is greatest 4, 1
• If treatment cannot be delayed, the lowest effective dose should be initiated with careful titration according to clinical response 1, 2

Known Fetal and Neonatal Risks

Intrauterine Growth Retardation (Primary Concern)

• Growth retardation is the most consistently documented adverse effect associated with propranolol use during pregnancy 4, 1, 5
• This risk appears particularly elevated with first trimester exposure 2
• Growth retardation has been statistically correlated with chronic propranolol therapy in clinical series 5

Neonatal Effects at Birth

• Neonates exposed to propranolol at parturition may exhibit bradycardia, hypoglycemia, and/or respiratory depression 3
• However, these effects (including hyperbilirubinemia, polycythemia, and neonatal apnea) are not invariable and have not been statistically correlated with chronic propranolol therapy in all studies 5
• Adequate facilities for monitoring infants at birth should be available 3

Other Reported Complications

• Small placentas and congenital abnormalities have been reported, though causality is difficult to establish 3
• Premature labor and metabolic abnormalities have been reported but may be secondary to fetal distress in high-risk pregnancies rather than drug effect 4

Required Monitoring Protocol

Maternal Monitoring

• More careful monitoring and dose adjustments are necessary as pregnancy-related physiologic changes affect drug absorption, bioavailability, and elimination 4
• Serial echocardiography may be warranted, particularly during the second or third trimester when hemodynamic load is highest 1, 2

Fetal Monitoring

• Closer monitoring of fetal growth via serial ultrasound is mandatory for pregnant women on beta-blockers 1, 2
• Surveillance for fetal bradycardia should be considered throughout pregnancy 1, 2
• Monitor for rare adverse effects including hypoglycemia and metabolic abnormalities in the newborn 2

Neonatal Monitoring

• Arrange early follow-up after hospital discharge 2
• In severely affected infants, short-term pharmacological management may be required 2

Dosing Strategy

• Start with the lowest effective dose and titrate according to clinical response 1, 2
• Use selective β1 beta-blockers when possible, as they theoretically interfere less with peripheral vasodilation and uterine relaxation 4

Comparison with Other Beta-Blockers

Metoprolol (Acceptable Alternative)

• Metoprolol receives a Class I recommendation for prophylactic therapy during pregnancy (stronger than propranolol's Class IIa) 4
• The European Society of Cardiology considers metoprolol safe during pregnancy and it may be preferred by some clinicians 1
• Consider switching to metoprolol if concerns about fetal growth arise 1, 2

Atenolol (Contraindicated)

• Atenolol should be completely avoided during pregnancy 1, 2
• Atenolol is FDA Category D and receives a Class III recommendation (should not be used) 4
• It has been associated with more pronounced intrauterine growth retardation, especially with early pregnancy exposure and longer duration of use 1, 2
• The European Society of Cardiology specifically states that "Atenolol should not be used for any arrhythmia" during pregnancy 1

Clinical Decision Algorithm

1. Assess necessity: Use antiarrhythmic therapy only if symptoms are intolerable or if tachycardia causes hemodynamic compromise; in patients with mild symptoms and structurally normal hearts, provide reassurance only 4

2. Timing evaluation: If possible, avoid initiation during the first trimester 4, 1

3. Drug selection: Choose propranolol or metoprolol over atenolol; metoprolol may be preferred given its Class I recommendation 4, 1

4. Dosing: Start with the lowest effective dose and titrate carefully 1, 2

5. Monitoring implementation:

   • Serial ultrasounds for fetal growth 1, 2
   • Fetal bradycardia surveillance 1, 2
   • Serial echocardiography in second/third trimester 1, 2

6. Delivery preparation: Ensure adequate facilities for neonatal monitoring at birth 3

Critical Pitfalls to Avoid

• Do not use atenolol under any circumstances 1, 2
• Do not assume that absence of symptoms means absence of fetal effects—growth retardation can occur without obvious maternal or fetal distress 5
• Do not discontinue monitoring after the first trimester; hemodynamic load is highest in the second and third trimesters 1, 2
• Do not overlook the need for neonatal monitoring at delivery, even if pregnancy has been uncomplicated 3

Risk-Benefit Context

• All antiarrhythmic drugs should be regarded as potentially toxic to the fetus 4
• However, untreated maternal arrhythmias or hypertension carry their own significant risks including hemodynamic compromise 4, 2
• The decision to use propranolol represents a balance between maternal cardiovascular stability and potential fetal effects, with the understanding that controlled maternal disease generally improves fetal outcomes 4