If people born with hearing loss have it caught early--as infants--many will be able to learn and communicate normally, unlike most children whose hearing problems are detected later as toddlers.

That's the theory behind a growing movement among audiologists, pediatricians and legislators who believe that the easiest, most effective way to find and treat babies with hearing loss is to screen all newborns before they are discharged from the hospital.

Study after study has shown that by the time most children with hearing loss are identified, generally at about 3 years old, the most critical period for speech and language development has already passed. Less serious cases of hearing loss often go undetected even longer.

According to the National Institutes of Health, serious hearing loss can have devastating results, ranging from delayed language to inadequate social and emotional development to poor academic performance.

But if hearing problems are caught soon after birth and children are fitted with hearing aids or are given some other form of immediate intervention, such as being taught sign language, their speech and language skills can develop normally, said Gilbert Herer, a professor of pediatrics at George Washington University Medical School and chair of hearing and speech at Children's National Medical Center in Washington.

"I'd be willing to bet that these babies that have been fitted with hearing aids will be in regular kindergarten and will be able to learn just like other kids," Herer said. "That's not the case with kids who are discovered at 2 1/2."

So far, 20 states, including Maryland and Virginia, have adopted laws that either expand access to newborn hearing screening programs or mandate hospitals to test hearing in all newborns before they go home. Infant hearing screening bills are pending in five states, while two others plan to study the need for legislation. In addition, bills to help states fund universal newborn hearing screening programs have been introduced in Congress.

Last year, only eight states had such laws on the books, said Jim Potter, director of government relations and public policy at the American Speech-Language-Hearing Association. "We are very pleased with the success we've had this year," Potter said. "We're going to try to redouble our efforts for the year 2000."

Such success, though, doesn't come without criticism. In a commentary published five months ago in the journal Pediatrics, physician Jack Paradise argues that the nation's pediatricians are moving too quickly to implement universal newborn hearing screening without full understanding of the potential costs.

"The problem is that we don't really know what the right thing to do is," says Paradise, a pediatrician at Children's Hospital in Pittsburgh. "There's a benefit side and there's a risk side. That risk side has never really been examined."

Paradise's main concern is errors that wrongly identify a child as having a hearing problem. "There is much evidence . . . that identifying a child as abnormal in the newborn period, even when that identification soon proves incorrect, can engender lasting anxiety on the part of certain parents and can have long-term adverse effects on parent-child relationships and on children's later psychological development," he states.

But Paradise admits that his views are in the minority and that the nationwide momentum for universal newborn hearing screening is picking up speed so fast that it's difficult for critics to be heard. Advocates say the push for universal screening is justified, backed by evidence that outweighs any drawbacks.

For every 1,000 babies born, about three have some sort of hearing impairment, making it the most common birth defect in the country, according to the National Center for Hearing Assessment and Management at Utah State University. And yet more than 85 percent of all hospitals do not screen hearing before newborns are discharged.

Instead, most hospitals screen only babies with high-risk factors for hearing loss, such as a family history of childhood hearing loss, low birth weight and facial deformities. But when states such as Virginia looked at data, officials discovered that about half the children later diagnosed with hearing problems had no identifiable risk factors at birth.

"We knew that we were missing 50 percent of babies," said Pat Dewey, speech and hearing services administrator at the Virginia Department of Health. "So the natural progression was to screen everyone."

Virginia passed its universal newborn hearing screening legislation last year, and as of July 1, every hospital in the state with a neonatal intensive care unit was required to screen all its newborns before discharge. The law extends to all Virginia hospitals next July.

Loudoun Hospital Center is one of 23 hospitals across the state that began its screening program last month. Since then, nurses have detected one baby with possible hearing loss. The infant, who had no high-risk factors, would probably have slipped through the cracks before the universal screening program began, said Nancy Sehnert, team leader of the hospital's nursery.

Maryland passed its universal screening legislation in April and will require all its hospitals to comply with the law beginning next July.

Holy Cross Hospital in Silver Spring has had a universal newborn hearing screening program for more than two years and screens 6,500 babies a year. Grant money helped start the program, which is managed by Herer of Children's National Medical Center. The pilot program has demonstrated that universal screening could be cost-effective at a very large hospital.

The push for universal screening wasn't possible until the early 1990s, when equipment was developed that evaluates babies' hearing by examining their brain waves. "As an audiologist, this is the dream of all dreams--that we'd be able to identify children with hearing loss as babies," Herer said.

Several other Maryland hospitals have tried to start programs in the past but were unsuccessful in maintaining them because of budgetary constraints, said Susan Panny, director of the Office of Hereditary and Congenital Disorders at the Maryland State Department of Health and Mental Hygiene.

The new Maryland law, which mandates insurance companies to pay for screening, will help ensure funding for screening. Once hospitals buy the proper equipment, the cost is between $25 and $40 per baby.

Michelle Reilly, of Odenton, says her 2-year-old son, Matthew, would never have had his hearing screened if it weren't for the program at Holy Cross. Although he had no high-risk factors, the screening detected a problem. At 4 1/2 months, audiologists confirmed that Matthew had no hearing in his left ear and some loss in his right ear. At 5 months, he was wearing hearing aids.

Although Matthew can't make out sounds as well as most children, tests show that his speech and language development is right on track.

"We're so incredibly lucky. Because they caught it early enough, we were able to get amplification for Matthew," Reilly said. "It's empowered us with time to do research and get knowledge and start working on things sooner rather than later."