ORIGINAL ARTICLE Cytomegalovirus transmission to extremely low-birthweight infants through breast milk S. DOCTOR 1 , S. FRIEDMAN 1 , M. S. DUNN 2 , E. V. ASZTALOS 2 , L. WYLIE 2 , T. MAZZULLI 3 , M. VEARNCOMBE 4 & K. O’BRIEN 5 1 Department of Paediatrics, University of Toronto, 2 Department of Newborn and Developmental Paediatrics, Sunnybrook and Women’s College Health Sciences Centre, 3 Department of Microbiology, Mount Sinai Hospital, 4 Department of Microbiology, Sunnybrook and Women’s College Health Sciences Centre, and 5 Department of Paediatrics, Mount Sinai Hospital, Toronto, Canada Abstract Aim: To determine the incidence, timing and clinical significance of acquired postnatal cytomegalovirus (CMV) in extremely low-birthweight (ELBW) infants. Methods: Prospective, longitudinal surveillance study. ELBW infants were recruited in the first week of life. Maternal blood was tested for CMV-specific IgG antibodies. Weekly urine samples were obtained from infants for CMV culture and rapid antigen testing. Data were collected regarding clinical course and breast milk intake. Results: Of 181 eligible infants, 119 infants, born to 101 mothers, were enrolled. Eighty of the 101 mothers had their serum checked for CMV status. Seventy percent of those tested were seropositive for CMV. Of the 65 infants born to seropositive mothers, 94% received breast milk during their hospital stay. Complete urine collection was obtained in 92 infants. CMV was cultured from the urine of only four infants, all of whom were born to seropositive mothers. Only one of these four infants was symptomatic. The range at which CMV was first detected was between 48 and 72 postnatal days of age. Conclusions: Despite a very high CMV seropositivity rate in mothers of ELBW infants, and the previously reported high rate of CMV excretion into breast milk, the incidence of postnatal CMV transmission was extremely low in our study. Key Words: Breast milk, cytomegalovirus, extremely low birthweight, postnatal cytomegalovirus infection, preterm infants Postnatally acquired cytomegalovirus (CMV) infection can cause serious clinical consequences in premature infants [1–3]. Acquisition of CMV through breast milk has been identified as the most important route of postnatal transmission [1,4,5]. This is especially concerning in populations where maternal CMV seroprevalence is high, combined with a high rate of breastfeeding. Transmission of CMV to infants who have been fed with CMV-positive breast milk has been reported to be as high as 38–70% [1,4–7]. Recent studies have demonstrated a higher rate of sympto- matic infection in smaller and more premature infants [1–3,7]. Extremely low-birthweight (ELBW 41000 g) in- fants make up a significant proportion of our neonatal intensive care population. There are limited data available regarding postnatal acquisition of CMV infection in this specific group. We therefore wished to determine the incidence, timing and clinical signifi- cance of postnatally acquired CMV in ELBW infants. The purpose was to determine whether further pro- cedures to prevent CMV transmission via breast milk are required in this high-risk population. Patients and methods Study design This was a prospective longitudinal surveillance study conducted in the neonatal intensive care units at Mount Sinai Hospital and Sunnybrook and Women’s College Health Sciences Centre, Toronto, Ontario, Correspondence: Shaheen Doctor, Department of Newborn and Developmental Paediatrics, Sunnybrook and Women’s College Health Sciences Centre, Women’s College Campus, 76 Grenville Street, Toronto, Ontario M5S 1B2, Canada. Tel: +1 416 323 6400 ext. 3369. Fax: +1 416 323 6274. E-mail: shaheen.doctor@swchsc.on.ca (Received 15 August 2003; revised 26 February 2004; accepted 24 March 2004) Acta Pædiatrica, 2005; 94: 53–58 ISSN 0803-5253 print/ISSN 1651-2227 online # 2003 Taylor & Francis DOI: 10.1080/08035250410022332