Evaluation of cytomegalovirus infections transmitted via breast milk in preterm infants with a real-time polymerase chain reaction assay

Objective. Preterm infants are at greater risk of symptomatic cytomegalovirus (CMV) infection than term infants. Breast milk is the main source of perinatal CMV infections. This study evaluated the kinetics of CMV load in breast milk and the rate of postnatal CMV transmission via breast milk from mothers to their preterm infants. Methods. This was a prospective study of 30 mothers and their 43 preterm infants. The infants either had a gestational age of <34 weeks or weighed <2000 g at birth. Breast milk, serum, and urine samples were collected every 2 weeks until discharge, and screened for CMV infection using a real-time PCR assay. Most of the breast milk had been preserved at -20degreesC before feeding to the preterm infants. Results. Twenty-four mothers (24 of 30, 80%), who had 34 preterm infants, were CMV immunoglobulin G positive. Twenty-one (87.5%) of the 24 seropositive mothers, who had 30 preterm infants, had detectable CMV deoxyribonucleic acid (DNA) in breast milk during the study period. Most breast milk became positive for CMV DNA 2 weeks after delivery. Viral DNA copy numbers increased until they peaked at 4 to 6 weeks. Afterward, the CMV DNA copy numbers decreased. Of the 30 infants who were fed CMV DNA-positive breast milk, CMV infection was confirmed in 3 infants. However, they had no clinical symptoms of CMV infection. Conclusions. Despite the high rate of CMV DNA in breast milk, symptomatic infections in the preterm infants did not occur. These results might be associated with the method of breast milk preservation and the population we studied. CMV infections transmitted via breast milk feeding did not have much impact on preterm infants in our institutes.