Very low birth weight infants fed breast milk from cytomegalovirus  (“CMV”)-positive mothers may be at an increased risk of developing postnatal CMV infection, says a new study published in JAMA Pediatrics.

Premature infants with very low birth weight (“VLBW”) are particularly vulnerable to CMV infection because of their immature immune systems. CMV infection can cause serious disease and, in some cases, can lead to death.In one of the largest studies of its kind, investigators evaluated blood transfusions and breast milk as potential CMV transmission sources. 539 infants in three neonatal intensive care units were tested at birth for evidence of congenital CMV infection, and again at regular intervals for ninety days.

29 out of the 539 infants acquired a postnatal CMV infection during the course of the study. Five infants infected with CMV developed severe disease or died. 27 of the 28 CMV infections occurred among infants fed CMV-positive breast milk. No CMV infections were linked to blood transfusion (blood products were CMV-seronegative and leukoreduced).

The study’s investigators estimate that between 10-20% of VLBW infants who are fed CMV positive breast milk from mothers with a history of CMV will develop postnatal CMV infection. In this study, 76% of mothers had been infected with CMV prior to giving birth.

Importantly, despite the potential risk, The American Academy of Pediatrics (“AAP”) Policy endorses routine breast milk feedings, even in CMV seropositive mothers. The AAP Policy suggests that benefits of breast milk feedings may outweigh the risks.