Most newborns have their hearing tested while they are still in the hospital, but those tests may not catch all severe hearing loss. One-third of children who were treated for deafness with cochlear implants had actually passed the newborn screening, according to a new study. That's important, because parents and pediatricians often don't realize that a baby has a serious hearing problem. Most states require that newborns' hearing be tested before they go home from the hospital. About 2 or 3 of every 1,000 children are born deaf or hard of hearing. The earlier those children get help, the better they do at developing language skills. Researchers at Children's Memorial Hospital in Chicago looked at the records of 127 children who had hearing problems severe enough to be treated with cochlear implants, and found that one-third of them had passed the newborn hearing test. The results were published in the latest Archives of Otolaryngology ? Head and Neck Surgery.