Nearly 55 percent of infants nationwide are put to bed with soft blankets or covered by a comforter, even though such bedding raises the chances of suffocation or sudden infant death syndrome, federal researchers reported Monday.

Their study, published in the journal Pediatrics, is the first to estimate how many infants sleep with potentially hazardous quilts, bean bags, blankets or pillows. Despite recommendations to avoid putting anything but a baby in a crib, two-thirds of black and Latino parents still use bedding that is both unnecessary and unsafe, the study also found.

“I was startled a little bit by the number of people still using bedding in the sleep area,” said Dr. Michael Goodstein, a neonatologist in York, Pa., who serves on a task force on sleep-related infant deaths at the American Academy of Pediatrics. “Sleeping face down on soft bedding increases the risks of SIDS 21-fold.”

Among the risk factors for SIDS, “bedding has fallen through the cracks,” said Dr. Thomas G. Keens, the chairman of the California SIDS Advisory Council. “This article is a wake-up call.”