Incidence of moderate to severe bilateral hearing impairment in newborns is 1-2 per 1000. In absence of screening, the median average age of congenital hearing impairment is at about 2-3 years of age. Screening focused in population at risk only identifies 50-60% of newborns with hearing impairment. 
There are no clinical trials comparing universal newborn hearing screening versus screening in case of risk factors or versus no screening, therefore there is no direct evidence on the benefits of screening.