Background Preterm infants are at risk of postnatal transmission of cytomegalovirus (CMV) via breast milk. Although most infants remain asymptomatic in the neonatal period, doubts about adverse effects on neurodevelopmental outcome have been raised. Pasteurisation prevents transmission of CMV via breast milk, which concomitantly inactivates immune and bioactive components. Data indicate that necrotizing enterocolitis (NEC) and late-onset sepsis (LOS) are less common in preterm infants fed with breast milk, as compared to infants fed with formula or pasteurised breast milk.

Aim To assess whether feeding preterm infants with unpasteurized breast milk i) decreases the rate of LOS and NEC and ii) increases the rate of postnatally acquired CMV infections.

Methods Between January 2008 and July 2013 preterm infants <32 weeks gestational age admitted to the neonatal intensive care unit Innsbruck (n = 341) were eligible for the study. Of those 323 fed with breast milk were retrospectively enrolled in the study. Two groups were formed with 164 infants being fed with unpasteurized and 159 infants with pasteurised breast milk.

Results The number of infants diagnosed with postnatally acquired CMV infections was significantly higher in the non-pasteurised group as compared to the pasteurised group (6.7% vs. 0.6%, p = 0.006). There was no significant difference regarding rate of LOS (15.9% vs. 15.1%, p = 0.486) or NEC (2.4% vs. 4.4%, p = 0.254).

Conclusion Feeding preterm infants with unpasteurized breast milk increases the rate of CMV infections. Of interest, we also show a non-significant trend to decreased rates of NEC, but this needs to be confirmed in larger studies.