Breast milk pasteurization for preventing cytomegalovirus infection: A preliminary study in a Japanese perinatal center.

Background: Postnatal cytomegalovirus (CMV) infection, primarily transmitted through breast milk, poses significant risks for very preterm infants (VPIs), potentially leading to sepsis-like syndromes, necrotizing enterocolitis, and pneumonia. Although pasteurization of breast milk has been shown to be effective in preventing postnatal CMV infection, no studies in Japan have examined its clinical efficacy in practice. This preliminary study investigated the incidence of postnatal CMV infection in VPIs born to CMV-seropositive mothers who received pasteurized breast milk at our Japanese perinatal center.

Methods: VPIs born before 32 weeks' gestational age (GA) from September 2019 to August 2023, excluding those born to CMV-seronegative or untested mothers, were retrospectively analyzed. Frozen-thawed breast milk was sterilized by Holder pasteurization at 63°C for 30 min. Urine CMV polymerase chain reaction (PCR) testing was routinely performed within the first 3 weeks of life and again at 36 weeks' corrected GA to assess CMV infection status.

Results: A total of 56 VPIs born to CMV-seropositive mothers underwent urine CMV PCR at 36 weeks' corrected GA to evaluate postnatal CMV infection. Among them, three cases (5.4%) were diagnosed with postnatal CMV infection; however, it remains unclear whether these cases were attributable to breast milk transmission or blood transfusions.

Conclusions: This preliminary study is the first in Japan to demonstrate that the incidence of postnatal CMV infection in VPIs born to CMV-seropositive mothers after receiving breast milk sterilized by Holder pasteurization was only 5.4%. These results support the effectiveness of our pasteurization protocol in preventing postnatal CMV infection.