What are the effects of propranolol (beta-blocker) on a pregnant female in labor?

Effects of Propranolol During Labor

Propranolol can be safely continued during labor in pregnant women who require it for maternal indications, but neonates must be monitored closely at birth for bradycardia, hypoglycemia, and respiratory depression. 1

Maternal Safety During Labor

• Propranolol does not need to be discontinued for labor and delivery, as vaginal delivery with Valsalva maneuvers has been shown to be well tolerated in women on beta-blockers 2
• The medication does not increase uterine contractility or cause premature labor 3
• Vaginal delivery is preferable to cesarean section to avoid the added stress of surgery, and cesarean section should be reserved only for obstetric or emergency cardiac indications 2
• Epidural or general anesthesia is reasonable during labor, with precautions taken to avoid hypotension 2

Critical Neonatal Effects at Birth

The FDA drug label explicitly warns that neonates whose mothers receive propranolol at parturition have exhibited bradycardia, hypoglycemia, and/or respiratory depression, requiring adequate monitoring facilities at birth. 1

Documented Neonatal Complications:

• Bradycardia: Propranolol crosses the placenta and can cause significant neonatal bradycardia immediately after delivery 1, 4, 5
• Hypoglycemia: Profound hypoglycemia has been documented in neonates exposed to propranolol at delivery, with beta-blockade impairing the infant's ability to mount a glycemic response 1, 4, 5
• Respiratory depression: Depressed respiration at birth has been reported in multiple cases 1, 4
• Rising drug levels post-delivery: Neonatal plasma propranolol levels can paradoxically rise in the first 4 hours after birth (from 40 ng/ml to 90 ng/ml in one documented case) due to drug redistribution and immature neonatal elimination mechanisms 5

Required Monitoring Protocol

Adequate facilities for monitoring infants at birth must be available when mothers are receiving propranolol at parturition. 1

Immediate Neonatal Assessment:

• Continuous cardiac monitoring for bradycardia in the first 24-48 hours 1, 4
• Serial blood glucose measurements starting immediately after delivery and continuing for at least 4-6 hours 1, 5
• Respiratory status assessment with readiness for ventilatory support 1, 4
• ECG monitoring, as drug effects may be apparent even without clinical symptoms 5

Dose Considerations

• Use the lowest effective dose of propranolol throughout pregnancy and during labor 6, 7
• Higher maternal doses (160 mg daily) have been associated with more severe neonatal complications 5
• The American College of Cardiology recommends titrating to clinical response rather than using fixed high doses 6

Key Clinical Pitfalls to Avoid

Do not assume that absence of maternal symptoms means the neonate will be unaffected - transplacental drug transfer occurs regardless of maternal response, and neonatal drug disposition differs significantly from adults 5

• Do not discharge the neonate early: Monitor for at least 24-48 hours as propranolol levels may rise post-delivery and complications can be delayed 5
• Do not rely solely on clinical appearance: ECG changes may be present even when the infant appears asymptomatic 5
• Do not confuse growth retardation with acute delivery complications: Intrauterine growth retardation is associated with chronic propranolol exposure throughout pregnancy 1, 8, while bradycardia, hypoglycemia, and respiratory depression are acute peripartum effects 1, 4, 5

Comparative Safety Context

• Propranolol and metoprolol are considered among the safer beta-blockers during pregnancy with longer safety records 2, 6, 7
• Atenolol should be completely avoided as it causes more pronounced intrauterine growth retardation 6, 7
• Labetalol is also considered safe and may be used as an alternative 2