The introduction of newborn-hearing screening has enabled early childhood hearing loss to be diagnosed and increased the number of children undergoing early care. Bilateral hearing loss is found in 0.08% of newborns and children whose hearing loss progresses or onset is delayed account for 4 to 30% of all pediatric hearing impairment. Children with perinatal risk factors tend to have deteriorated hearing or delayed-onset hearing loss in early childhood, necessitating audiometric follow-up. We also are aware of some children without risk factors who develop hearing impairment during infancy or early childhood. Hearing deterioration may be difficult to diagnose objectively, especially in young children, the presence of risk factors must be determines as soon as possible, especially given the lack of hearing management and close examination of children without apparent risk factors. We retrospectively studied children born from April 1998 to March 2007 and undergoing cochlear implantation as of April 2008. Among cases, we focused on 10 whose hearing impairment advanced during infancy -4 with risk factors known before hearing deterioration progressed, and 6 cases thought not to have any risk factors. We detected enlarged vestibular acquaduct in 3 of these 6 cases, and 3 more of whom had no risk factors -2 passing newborn-hearing screening and 1 in whom such screening detected hemilateral hearing loss. Our results underscore the need for early temporal computed tomography for detecting enlarged vestibular aquaduct. Even children with mild or hemilateral hearing loss should undergo audiometric and developmental testing at least every 6 months up to going to elementary school. Children suspected of impaired hearing should undergo thorough hearing tests regardless of newborn hearing-screening results to catch any problems early. Appropriate regular hearing and language development check-up tests must also be developed.