In a woman in her second trimester who requires beta‑blockade, can propranolol be continued on an as‑needed (PRN) basis, and what is the recommended dose and monitoring?

Propranolol PRN Continuation in Second Trimester

Propranolol can be continued during the second trimester for women requiring beta-blockade, but PRN (as-needed) dosing is not the recommended approach—scheduled dosing at the lowest effective dose with close fetal monitoring is preferred. 1, 2

Dosing Strategy

The American Heart Association and European Society of Cardiology recommend propranolol as a relatively safe first-line beta-blocker during pregnancy, but emphasize scheduled rather than PRN administration: 3, 1

• Start with the lowest effective dose (typically 10-40 mg for situational symptoms, or 80-160 mg daily divided into 2-3 doses for chronic prophylaxis) 2
• Titrate according to clinical response rather than using fixed high doses 1, 2
• Avoid first trimester exposure when possible, though you are already past this critical window in the second trimester 3, 1, 2

Required Monitoring Protocol

Since you are in the second trimester when hemodynamic load increases significantly, implement the following surveillance: 1

• Serial fetal growth ultrasounds beyond routine prenatal care to detect intrauterine growth retardation (IUGR), the primary fetal risk with propranolol 1, 2, 4
• Fetal echocardiography to monitor for bradycardia, particularly during second and third trimesters 1, 2
• Maternal blood pressure and heart rate monitoring at clinic visits, though routine monitoring between appointments is unnecessary if clinically stable 3, 1

Critical Safety Considerations

Intrauterine growth retardation is the most significant concern with propranolol use during pregnancy, particularly with longer duration of treatment: 1, 2, 4

• Growth retardation appears statistically significant in multiple case series, though other reported complications (hypoglycemia, hyperbilirubinemia, bradycardia) are not invariable 4
• The risk is lower than with atenolol, which is absolutely contraindicated and causes more pronounced IUGR 1, 2, 5
• Metoprolol may be preferred by some clinicians as an alternative with potentially less fetal growth impact 1, 5

Common Pitfalls to Avoid

• Never switch to atenolol—it is explicitly contraindicated (Class III recommendation) due to significantly worse fetal outcomes 1, 2, 5
• Do not use PRN dosing for chronic conditions—scheduled dosing provides more stable drug levels and better fetal tolerance 3, 2
• Avoid abrupt discontinuation if stopping therapy, though propranolol can generally be safely stopped without gradual weaning in most cases 2
• Do not delay monitoring—serial ultrasounds should begin now in the second trimester, not wait until third trimester 1

Clinical Decision Algorithm

1. Assess indication severity: Is beta-blockade truly necessary, or could non-pharmacological approaches suffice? 2
2. Verify no contraindications: Screen for asthma, cardiac failure, Raynaud disease, AV block, or depression 2
3. Convert PRN to scheduled dosing: Use the minimum effective dose divided 2-3 times daily rather than as-needed administration 3, 2
4. Establish monitoring schedule: Arrange serial growth ultrasounds and fetal echocardiography now 1, 2
5. Consider metoprolol switch: If concerns about fetal growth arise, metoprolol is an acceptable alternative with similar safety profile 1, 5

Postpartum Planning

Propranolol should be continued throughout pregnancy and the postpartum period if indicated for conditions like long QT syndrome, and is considered safe during breastfeeding with minimal infant exposure through breast milk 3, 2, 6