Is it safe for a breastfeeding woman to take aspirin (acetylsalicylic acid)?

Low-Dose Aspirin is Safe During Breastfeeding

For lactating women using low-dose aspirin (≤100 mg/day) for vascular indications who wish to breastfeed, continuing this medication is recommended. 1

Dose-Dependent Safety Profile

The safety of aspirin during breastfeeding is critically dependent on the dose:

Low-Dose Aspirin (<100 mg/day) - SAFE

• The American College of Chest Physicians explicitly recommends continuing low-dose aspirin during breastfeeding (Grade 2C recommendation). 1
• Acetylsalicylic acid itself is undetectable in breast milk even with highly sophisticated laboratory methods after 81 mg daily dosing. 2
• Only the metabolite salicylic acid appears in milk at very low concentrations (average 24 ng/ml), with a relative infant dose of only 0.4%. 2
• Low-dose aspirin (<100 mg/day) used late in pregnancy showed no significant effects on neonatal platelet function, suggesting minimal infant exposure. 1
• A prospective study of 15 breastfeeding mothers taking aspirin therapy documented no negative effects on infants. 1

High-Dose Aspirin (>100 mg/day) - AVOID

• High doses (several grams per day) pose real risks: metabolic acidosis has been documented in breastfed infants of mothers taking several grams daily. 1
• Potential risks include platelet dysfunction, gastrointestinal bleeding, and theoretically Reye syndrome in nursing infants exposed to high maternal doses. 1
• Salicylates are excreted into breast milk in proportion to maternal dose. 1

Pharmacokinetic Rationale

The favorable safety profile of low-dose aspirin relates to its pharmacokinetic properties:

• Aspirin is a polar, acidic drug that is poorly lipid soluble and highly protein-bound (>90%), limiting transfer into breast milk. 1
• At low doses (81 mg), the parent compound (acetylsalicylic acid) is below the limit of quantification in all milk samples tested. 2
• The metabolite that does appear (salicylic acid) reaches subclinical concentrations in infants. 2

Clinical Algorithm for Decision-Making

Step 1: Determine the aspirin dose

• If ≤100 mg/day → Continue breastfeeding without interruption 1
• If >100 mg/day → Consider alternative antiplatelet agents or reduce dose to ≤100 mg/day if clinically appropriate 1

Step 2: Assess the indication

• For vascular indications (cardiovascular disease prevention, history of preeclampsia): Low-dose aspirin is specifically recommended during lactation 1
• For pain/inflammation requiring high doses: Switch to alternative NSAIDs like ibuprofen, which has extensive lactation safety data 3

Step 3: Monitor the infant (if any concerns)

• Watch for unusual bruising or bleeding (though not expected at low doses) 1
• No routine laboratory monitoring is needed for infants of mothers on low-dose aspirin 2

Critical Caveats

The FDA label states to "ask a health professional before use" if breastfeeding, reflecting general caution rather than specific contraindication. 4 This conservative labeling should not override the evidence-based guideline recommendations from the American College of Chest Physicians. 1

Do not confuse pregnancy recommendations with lactation recommendations: While aspirin should be avoided in the last trimester of pregnancy due to effects on the fetus and labor, these concerns do not apply to the breastfeeding period. 4, 5

The theoretical risk of Reye syndrome has never been documented in breastfed infants of mothers taking low-dose aspirin, and remains purely theoretical even at higher maternal doses. 1