Objective: Incidence and significance of postnatal CMV transmission by breast milk in premature infants.

Design: Prospective study of mother-child pairs with preterm birth before 32 weeks(w) or birth weight <1500g. Exclusion of donor breast milk and of transfusions of CMV seropositive blood.

Material: Maternal CMV serostatus; ear swab of the infant; sequential screening of breast milk and children's urine. Methods: CMV-DNA-PCR and viral cultures on fibroblasts.

Results: Within a 8 months period 42 mother-child pairs were studied 24 mothers (57%) were CMV seronegative at birth; breast milk samples and the infants urine remained CMV negative. 18 mothers were CMV IgG seropositive (CMV IgM negative); 16/18 (88%) excreted CMV by breast milk(onset of excretion: day 8 (7-44) [median,range]; duration 34 (9-95)days). CMV transmission occurred in 7/42 pairs (17%), 8 infants were infected. In 4 patients (GA: 28-30 w) CMV was detected at an postnatal age of 8-12w, none of these infants had clinical signs of infection. However, 4 ELBW (GA:24-25w) were infected at an age of 4-7w, all infants had marked symptoms of an acute CMV infection: sepsis-like symptoms (n=3), cholestasis (n=1), thrombocytopenia(n=3), neutropenia (n=2).

Conclusion: In mothers of preterm infants a high incidence of CMV excretion into breast milk was detected. The most immature infants were at greatst risk to acquire an early and symptomatic CMV infection.