Adenovirus infection is a rare, but serious infection, during the neonatal period. The actual model of infection at birth is currently unknown, however, several mechanisms have been proposed. We describe a case of fatal neonatal adenovirus pneumonia in a 25-wk gestational age infant. Adenovirus was confirmed by electron microscopy and by in situ hybridization. The maternal cervical/endocervical smear taken prior to the delivery contained epithelial cells with changes suggestive of adenovirus, which was confirmed by in situ hybridization on the smear. These findings suggest that ascending viral infection is a factor in the pathogenesis of neonatal adenovirus infection. The identification and reporting of adenovirus may be important during pregnancy in order to avoid delay in delivery of the fetus once membranes have ruptured.