In Reply We thank Thomas et al for their question regarding head circumference growth and postnatal cytomegalovirus infection in very low-birth-weight (VLBW) infants. It is well established that congenital cytomegalovirus (CMV) can cause congenital microcephaly, and while most infants with congenital CMV are normocephalic at birth and continue to be so at follow-up, a very small percentage do develop microcephaly later.1 In our retrospective cohort study,2 we found no differences in the head circumference at birth (prior to CMV infection) or at discharge/postmenstrual age 40 weeks between VLBW infants identified as having postnatal CMV infection (n = 273) and those without (n = 273).2 Several other small prospective studies have reported similar findings. In a case-control study, Neuberger et al3 found no difference in the head circumference at discharge between VLBW infants with postnatal CMV (n = 40) and those without (n = 40).3 In addition, 3 prospective studies4-6 from 2 cohorts of VLBW infants with and without postnatal CMV found no differences in head circumference at 12 months (n = 14 infected; n = 41 uninfected), 24 months (n = 14 infected; n = 41 uninfected), 2 to 4.5 years (n = 22 infected; n = 22 uninfected), and school age (n = 20 infected; n = 21 uninfected).4-6 These 3 studies also compared neurodevelopmental outcomes of infants with and without postnatal CMV. Jim et al4 found no differences at 12 and 24 months. The other 2 studies evaluated the same cohort of infants over time and found no differences at 2 to 4.5 years, but significantly decreased motor and cognitive function at school age in infants with postnatal CMV.5,6