More than half of infants in the United States are being placed to sleep with bedding that puts them at greater risk of sudden infant death syndrome (SIDS), researchers warned in a report on Monday.

The National Institutes of Health (NIH), the Centers for Disease Control and Prevention, and other institutions found that despite regular warnings, unsafe bedding threatened nearly 55 percent of infants.

Cuddly toys and loose bedding, such as thick blankets, quilts and pillows, can obstruct an infant’s airway and pose a suffocation risk, the NIH has warned.

The organization has reiterated safety guidelines that infants should be placed to sleep alone, on their backs, on a firm sleeping surface such as a mattress in a safety-approved crib, covered by a fitted sheet.

The research found that unsafe bedding use dropped sharply from 85.9 percent in 1993-1995 but remained high at 54.7 percent in 2008-2010.

“Parents have good intentions but may not understand that blankets, quilts and pillows increase a baby’s risk of SIDS and accidental suffocation,” said the study’s first author, Carrie K. Shapiro-Mendoza, of the CDC’s Division of Reproductive Health in Atlanta.

The study, published online in Pediatrics, is an analysis of data taken from the National Infant Sleep Position Survey (NISP), which collected information on the influence of infant sleep position and safe sleep recommendations on infant care practices.

The survey collected information from a random sample of more than 1,000 caregivers in US households between 1992-2010.

Study author Marian Willinger said parents often received “mixed messages” about the kinds of bedding to be used with infants.

“Relatives may give them quilts or fluffy blankets as presents for the new baby, and they feel obligated to use them. Or they see magazine photos of babies with potentially unsafe bedding items. But babies should be placed for sleep on a firm, safety approved mattress and fitted sheet, without any other bedding,” she said.

SIDS is the unexplained death of a child within the first year of life. The rate of SIDS in the United States has fallen 50 percent since 1992, amid a welter of campaigns to raise awareness about safe bedding practices.

However, the decline has slowed since 2000 while the number of other unexpected infant deaths from causes such as accidental suffocation or entrapment in bedding material has increased.