What are the safe beta blockers (beta-adrenergic blocking agents) for use in pregnant women?

Safe Beta Blockers in Pregnancy

Metoprolol and labetalol are the safest beta blockers for use in pregnancy, with metoprolol preferred over other beta-1 selective agents due to lower rates of fetal growth restriction compared to atenolol. 1

First-Line Beta Blocker Selection

Preferred Agents

• Metoprolol is the preferred beta blocker during pregnancy because it has a lower incidence of fetal growth retardation compared to atenolol, making it the optimal choice among beta-1 selective agents. 1

• Labetalol (an alpha-beta blocker) is considered safe and effective with extensive safety data spanning decades of use for various maternal conditions during pregnancy. 1 Labetalol offers the advantage of vasodilation through its alpha-blocking properties. 1

• Propranolol is considered relatively safe as a first-line agent for chronic prophylaxis during pregnancy, particularly for arrhythmias, due to its longer safety record. 2

Agents to Avoid

• Atenolol should be avoided during pregnancy as it has been specifically associated with more pronounced intrauterine growth retardation, especially when used early in pregnancy and for longer duration. 2, 3 Studies show significantly lower birth weights with atenolol (2750 ± 630 g) compared to labetalol (3280 ± 555 g). 3

Clinical Application Algorithm

For Acute Treatment of Arrhythmias

• Intravenous metoprolol or propranolol is reasonable for acute treatment of supraventricular tachycardia when adenosine is ineffective or contraindicated, using slow infusion to minimize hypotension risk. 1

For Chronic Hypertension Management

• Start with extended-release nifedipine or labetalol as first-line agents for chronic hypertension during pregnancy, initiating treatment when blood pressure reaches 150-160/100-110 mmHg. 4

• Labetalol dosing: 100 mg twice daily, titrating up to 2400 mg per day as needed. 1

• Metoprolol is preferred over atenolol if a beta-1 selective agent is specifically indicated. 1

For Rate Control in Valvular Disease

• Beta blockers with beta-1 selectivity are preferred for rate control in pregnant patients with mitral stenosis to avoid beta-2 effects on uterine relaxation. 1

Important Safety Considerations and Monitoring

Timing of Initiation

• Avoid beta blockers during the first trimester if possible, when the risk of congenital malformations is greatest. 2

• Use the lowest effective dose initially, with dose adjustments made according to clinical response. 2

Fetal Monitoring Requirements

• Serial echocardiography may be warranted, particularly during the second or third trimester when hemodynamic load is highest. 2

• Closer monitoring of fetal growth is recommended for all pregnant women on beta blockers due to the association with intrauterine growth retardation. 2, 5

• Surveillance for fetal bradycardia should be considered throughout pregnancy. 2

Neonatal Considerations

• Labetalol may cause potential neonatal bradycardia and carries risk of small for gestational age infants. 4

• Hypotension, bradycardia, hypoglycemia, and respiratory depression have been reported in infants of mothers treated with labetalol during pregnancy. 6

Comparative Effectiveness Data

• Recent large-scale analysis shows labetalol and nifedipine have similar effectiveness and safety for treating chronic hypertension during pregnancy, with no significant difference in composite outcomes of severe preeclampsia, medically indicated preterm birth, placental abruption, or stillbirth (adjusted RR 1.03,95% CI: 0.96-1.11). 7

• Both labetalol and nifedipine show similar rates of small for gestational age infants (13% vs 12%, adjusted RR 0.98,95% CI: 0.82-1.16). 7

Common Pitfalls to Avoid

• Never use atenolol as a first-line agent despite it being a beta blocker—the evidence clearly demonstrates increased fetal growth restriction compared to other options. 1, 2

• Do not assume all beta blockers are equivalent—the choice matters significantly for fetal outcomes, with metoprolol and labetalol having superior safety profiles. 1, 3

• Avoid combining labetalol with calcium channel blockers like verapamil due to increased risk of bradycardia and heart block. 6

• Be aware that beta blockers blunt the reflex tachycardia from nitroglycerin, which may require dose adjustments if used concomitantly. 6