Detecting hearing impairment in babies early can improve their language ability later, a study suggests.
All new parents are now offered hearing tests for their babies
Southampton researchers studied 120 children aged eight with permanent hearing impairment, half of whom were diagnosed in screening tests.
Those who did not have their impairment confirmed before they were nine months old scored worse in language skills tests than those who had.
The research appeared in the New England Journal of Medicine.
However, the study also concluded that a hearing impaired child's speech was not greatly benefited by early detection.
One in 750 children are born in the UK with moderate, severe or profound bilateral permanent hearing impairment.
Reader in child health at Southampton University Dr Colin Kennedy said: "Our study extends findings from previous studies in the relationship between early identification of hearing impairment and later outcomes."
He said that until now it had not been certain whether universal screening of newborn babies for hearing impairment had any effect on the child's later verbal abilities.
"Screening and early confirmation of permanent childhood hearing impairment clearly do have clinically important benefits to the language abilities of children at primary school age," he said.
But he suggested that a longer-term follow-up was needed to establish whether children continue to show "superior language skills and have a higher academic achievement" at secondary school level.
All parents in England are now offered hearing tests for their babies shortly after birth.
The research team said its study vindicated the Department of Health's decision to offer these screening testes.
It also showed there was a "sensitive period" during infancy when exposure to the sounds of language was particularly important for the brain development needed for language, the team said.
Gwen Carr, director of UK services for the National Deaf Children's Society, said she welcomed the research, which backs earlier studies showing the longer-term benefits of early screening.
"Before screening was introduced, late identification of deafness caused many problems for children and their families - often with long-term consequences.
"We know from our work supporting families, how frustrating it was for them not being sure why their child was struggling to develop speech and how upsetting it was watching their child become frustrated at not being able to communicate.
"For the child, late identification has frequently led to a life of under-achievement, both socially and educationally," she added.