Frozen Breast Milk Storage Safety
Frozen breast milk stored at standard home freezer temperatures (-18°C to -20°C) is safe to thaw and serve for up to 3-4 months, though it remains bacteriologically safe for longer periods with some nutritional degradation.
Storage Duration Guidelines
For optimal nutritional quality, use frozen breast milk within 3-4 months when stored at -18°C to -20°C. 1
- Breast milk can be safely stored at -20°C for up to 1 month from a bacteriological standpoint, with substantial decreases in bacterial counts observed after thawing 2
- Storage for longer periods (up to several months) remains bacteriologically safe, but nutritional changes occur 3, 1
- If you have access to a deep freezer at -70°C, this is the preferred method for longer-term storage as it better preserves milk properties 3
Nutritional Changes During Freezing
The longer milk is frozen, the more nutritional alterations occur:
- Fat content decreases and free fatty acids increase as freezing duration extends 1
- Protein content initially increases at 2 days but decreases significantly after 1 week of freezing 1
- Energy content decreases after 8 weeks of frozen storage 1
- Carbohydrate content increases at 2 days but shows no significant change after 1 week 1
- Some bioactive components (glutathione peroxidase, antioxidant capacity, lactoferrin) decrease with freezing, though most immunological factors remain stable 1
Safe Thawing Practices
Thaw frozen breast milk at room temperature (ambient temperature) and use within 6 hours of complete thawing. 4
- Never thaw breast milk in warm water baths, as this risks contamination with waterborne pathogens and reduces bacterial viability 4
- Once thawed, milk should not be refrozen 3
Practical Recommendations
Write the expression date on each storage container immediately after pumping so you can use the oldest milk first and minimize storage duration 1
- Prioritize using milk that has been frozen for shorter periods to maximize nutritional quality 1
- Standard home freezer storage (-18°C to -20°C) is acceptable and practical for most families 3, 2
- Fresh refrigerated milk (stored at 4°C for up to 72 hours) is preferable to frozen milk when feasible, as it maintains better nutritional properties 3, 2
Important Caveat for Preterm Infants
For preterm infants whose mothers are CMV-positive, be aware that freezing at -20°C for up to 2 months does not reliably inactivate cytomegalovirus. 5 This is a specific concern requiring discussion with the neonatal care team.