CMV transmission in human milk

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Clinicians are encouraging women to provide milk for their preterm infants. A well-known risk is that fresh human milk can transmit CMV to the newborn. However, the risks are poorly defined. There are strategies to limit transmission, such as freezing or pasteurizing the milk prior to feeding the infant. However, such manipulations change the properties of the milk and may limit its benefits. Capretti et al report a careful virology study quantifying transmission of CMV from their mothers' fresh milk to preterm infants. For a population of 80 infants, 32% were fed CMV culture positive milk and 11% of the infants became CMV positive with the same genotype that was cultured from the milk. Of the 9 preterm infants infected with CMV, 3 had a mild sepsis-like illness and 5 others had mild neutropenia and hyperbilirubinemia. Some of the infants were treated empirically with IVIG, which may have limited transmission or symptoms, although this use of IVIG has not been validated. The infants were doing well at 2 years, and the authors conclude that CMV transmission from human milk causes a mild and self-limited disease. However, severe cases of CMV pneumonia can occur, and the small number of cases identified in this series is inadequate to establish risk. It remains to be determined if the possible benefits of feeding preterm infants fresh CMV positive milk is worth the probable risks to some infants.