The Benefits and Biological Risks in Breastfeeding and Sharing Human Milk: Have We Got it Right?

Implementation of the strong recommendation by the World Health Organization (WHO), the United Nations Children's Fund (UNICEF), and others, to increase use of donor human milk in cases where breastfeeding cannot be provided, requires a flexible, knowledge-based and risk-informed approach.

Based on an extensive literature review, we present the evidence for potential biological risks of breastmilk in three scenarios: fresh, unmodified milk from breast to baby (breastfeeding and wet-nursing); expressed and unmodified milk stored at < 4 ºC until just before consumption; and milk modified by some form of pasteurization.

With the exception of contamination by some viruses and syphilis, breastfeeding is the safest way to feed a baby, despite its highly variable microbiome and virome-including organisms that, in other circumstances, can cause disease. Wet-nursing, where the donor has been appropriately screened, carries a similar risk profile to mother's own feeding. Whilst expression and storage of raw milk at < 4 °C adds a bacterial load, the additional risk, with knowledge and screening of the donor and careful attention to all steps in delivery, seems small and is smaller than using bovine-based formulae-especially in low resource circumstances. Donated milk from unknown donors carries additional risks. A decision to reduce these risks through thermal pasteurization must be weighed against the loss of breastmilk's natural protective components.

Not only have the biological risks of both informal and formal milk sharing for healthy infants been greatly exaggerated, but that they are often quoted without consideration of the overall risks of alternatives.