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

Propranolol Safety in Pregnancy

Propranolol is relatively safe for use during pregnancy when clinically necessary, but should ideally be avoided during the first trimester and used at the lowest effective dose with close fetal monitoring throughout pregnancy. 1, 2

Safety Classification and Guideline Recommendations

• 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
• Propranolol is FDA Pregnancy Category C, meaning animal studies show potential risk but human data are limited 3, 4
• For acute conversion of supraventricular tachycardia, propranolol receives a Class IIa recommendation (reasonable to use) 3
• For prophylactic therapy of arrhythmias, propranolol receives a Class IIa recommendation with Level B evidence 3

Trimester-Specific Considerations

First Trimester:

• Beta-blockers including propranolol should be avoided during the first trimester if possible, when the risk of congenital malformations and growth retardation is greatest 3, 1, 2
• Intrauterine growth retardation has been specifically associated with first-trimester propranolol exposure 1, 2, 5

Second and Third Trimesters:

• Propranolol may be used when benefits outweigh risks, though monitoring remains essential 1, 2
• Serial echocardiography is warranted particularly during the second and third trimesters when hemodynamic load is highest 1, 2

Known Fetal and Neonatal Risks

Established Risk:

• Intrauterine growth retardation is the most consistently documented adverse effect and appears statistically significant 1, 2, 5

Potential but Inconsistent Risks:

• Fetal bradycardia, hypoglycemia, and respiratory depression at birth have been reported but are not invariable 3, 4, 5
• Hyperbilirubinemia, polycythemia, and neonatal apnea cannot be statistically correlated with chronic propranolol therapy 5
• Small placentas and congenital abnormalities have been reported, though causality is unclear 4

Required Monitoring Protocol

• Fetal growth surveillance: Closer monitoring via serial ultrasound is recommended throughout pregnancy 1, 2
• Fetal heart rate: Surveillance for fetal bradycardia should be maintained throughout pregnancy 1, 2
• Neonatal monitoring: Adequate facilities for monitoring infants at birth should be available for bradycardia, hypoglycemia, and respiratory depression 4
• Metabolic monitoring: Watch for rare adverse effects including hypoglycemia and metabolic abnormalities in the newborn 2

Dosing Strategy

• Start with the lowest effective dose initially 1, 2
• Titrate according to clinical response 1, 2
• The pharmacokinetics of propranolol are not significantly altered during pregnancy, so dose adjustments based solely on pregnancy are not necessary 6

Comparison with Other Beta-Blockers

Preferred alternatives:

• Metoprolol is also considered safe during pregnancy and may be preferred by some clinicians as an alternative if growth concerns arise 1, 2
• Both propranolol and metoprolol are acceptable choices 3, 1

Avoid completely:

• Atenolol should not be used for any arrhythmia during pregnancy as it has been associated with more pronounced intrauterine growth retardation, especially with early and prolonged exposure 3, 1, 2
• Atenolol is FDA Pregnancy Category D 3

Clinical Decision Algorithm

1. Assess clinical necessity: Use propranolol only if symptoms are intolerable or if tachycardia causes hemodynamic compromise 3
2. Timing consideration: Delay initiation until after first trimester if clinically feasible 3, 1, 2
3. Initial dosing: Start with lowest effective dose 1, 2
4. Monitoring initiation: Establish baseline fetal growth parameters and plan serial ultrasounds 1, 2
5. Alternative consideration: If growth retardation develops, consider switching to metoprolol 2
6. Delivery preparation: Ensure neonatal monitoring capabilities are available at delivery 4

Critical Pitfalls to Avoid

• Do not use atenolol as it has worse fetal outcomes than propranolol 2
• Do not assume safety without monitoring - even though propranolol is relatively safe, fetal growth surveillance is mandatory 1, 2
• Do not withhold when truly indicated - untreated maternal arrhythmias causing hemodynamic compromise pose their own risks to both mother and fetus 3
• Do not forget delivery planning - neonates may exhibit bradycardia, hypoglycemia, or respiratory depression at birth requiring immediate monitoring 4