Transmission of cytomegalovirus to preterm infants through breast milk

OBJECTIVE: To evaluate the rate of virus excretion through breast milk and the incidence and significance of postnatal cytomegalovirus (CMV) transmission from mothers to premature infants. DESIGN: Prospective study of mother-child pairs after preterm delivery before 32 weeks or birth weight < 1500 g. Exclusion of donor breast milk and of CMV-seropositive blood. Material used was maternal CMV serostatus, ear swab of the infants at birth, sequential screening of breast milk and children's urine. Methods used were CMV-DNA PCR and viral cultures on fibroblasts. RESULTS: During a 12-month period 56 mother-infant pairs with 67 preterm infants were studied. Twenty-seven women (48%) were CMV-seronegative at birth; breast milk samples and the infants' urine remained CMV-negative. Twenty-nine women were CMV IgG-seropositive; 23 of 27 seropositive breast-feeding mothers excreted CMV through milk (85%); 25 of 27 (93%) had CMV DNA-positive results. CMV infection occurred in 17 of 67 infants (25%). CMV transmission was exclusively found in infants of seropositive mothers who excreted CMV and breast-fed their infants; 17 of 29 exposed infants became infected (59%). In 12 patients (gestational age, 29.9 +/- 1.8 weeks) CMV was detected at a postnatal age beyond 8 weeks; 5 of these infants had mild signs of a viral infection. However, 5 extremely low birth weight infants (gestational age, 24.4 +/- 0.5 weeks) were infected at an age of 4 to 7 weeks; 4 of these infants had marked symptoms of an acute CMV infection. CONCLUSION: In mothers of preterm infants a high incidence of CMV excretion into breast milk was detected. There is evidence that the most immature infants are at the greatest risk to acquire an early and symptomatic CMV infection.