Although the practice is viewed as essential to keeping babies safe, nearly a third of all caregivers still don't regularly put infants on their backs to sleep, according to a new report published Monday.

Despite guidelines from pediatricians and a national educational campaign in place since the mid-1990s, researchers found that while there was a dramatic increase in back-sleeping during the first years of the push, the percentage of parents following the recommendations has been virtually unchanged since 2001 — holding at just over 70 percent — although that's still a substantial improvement from the 25 percent rate in 1993.

Pediatricians and the National Institute of Child Health and Human Development called for the change in sleeping practices in the face of a large body of evidence that placing infants on their backs reduced the risk of sudden infant death syndrome, the leading cause of infant death in the first year of life in the United States.

And, in fact, deaths attributed to SIDS have decreased by about 50 percent since 1993, largely due to the safe-sleep guidelines, but that decline has also flattened in recent years. Federal statistics show that more than 4,000 babies still die suddenly and unexpectedly each year — a number that hasn't changed much each year since 2003.

For the study, led by Dr. Eve Colson of Yale University School of Medicine, scientists analyzed data from an annual national phone survey on infant nighttime sleep practices done between 1993 and 2007. The findings are published in the Archives of Pediatric and Adolescent Medicine.

Colson's team noted the leveling off of back sleeping, but also found that three issues seem to most influence whether mothers and other caregivers follow the guidelines: having a doctor recommend placing the baby on his or her back; a fear that the baby will choke; and concerns for the infant's comfort.

The surveys found that from 2003 to 2007, more than 45 percent of mothers reported either not getting any advice from their physician about placing the baby to sleep on the back or being advised not to place the baby in that position.

"If we can teach people that comfort and choking are not issues and if we can make sure that doctors advise their patients that the back is the only safe place for infant sleep, then we may be able to overcome this leveling off of the practice," Colson said.

Marian Willinger, special assistant for SIDS research at the NICHD, which funded the Colson study, said, "We're continuing our efforts to make sure health professionals know, and tell their patients, that infants sleep safest on their backs." She noted that the "Back to Sleep" campaign also targets nurses and other health professionals, including a new outreach soon to be aimed at pharmacists.

Willinger also noted that while there may be rare instances when a physician may have a sound medical reason for not having a baby sleep on the back, for the vast majority, worries about choking or not sleeping well "are unfounded."

Another recent study, published in September by Dr. Rachel Moon and colleagues at the Children's National Medical Center in Washington, found that many of the popular media depictions of babies at rest contradict the safe-sleep practices advocated by experts.

The researchers analyzed pictures of sleeping babies in 24 magazines with a wide circulation among women ages 20 to 30. The photos, both accompanying articles and ads, were reviewed for infant sleep position and a safe-sleep environment.

Moon and her team found that more than a third of the photos showed the infant in an unsafe position — not on the back. And more than two-thirds of sleep environments shown were hazardous.

There is growing evidence being generated by more complete infant-death investigations that many deaths still attributed to SIDS may actually be due to suffocation that occurs when babies are allowed to sleep with adults or siblings in beds or on sofas, or are improperly placed in cribs with too much bedding, pillows or overly soft mattresses. "There are major discrepancies between what doctors recommend to prevent SIDS and what moms may see in mainstream media," Moon said. "The most important thing for moms to realize is that what they see in magazines may not be what's best for their baby in real life."