Pediatricians have been telling parents for years to put babies to sleep on their backs and keep soft bedding such as blankets, bumpers, stuffed animals or pillows out of cribs. But despite decades of warnings and recommendations, a new study from the American Academy of Pediatrics (AAP) found an alarming number of babies still sleep in unsafe ways, increasing the risk of sudden infant death syndrome (SIDS).

This study may be more revealing than previous similar ones because researchers used video cameras to watch more than 160 babies while they slept for one night at three points during infancy: 1 month old, 3 months old and 6 months old. Previously, researchers simply asked parents how they put their infants to sleep, but in this study researchers could watch for themselves.

Researchers found more than 90 percent of one-month-old babies had loose items on their sleep surface. Nearly 20 percent of three-month-old babies were put to sleep on their sides or stomach. And at six months old, more than 30 percent were put to sleep on their sides or bellies, and more than 90 percent had loose items in their cribs.

"Most parents, even when aware of being recorded, placed the infants in environments with established risk factors for sleep-related infant deaths, including positioning the children on their sides or stomachs; soft sleep surface; loose bedding; or bed-sharing. Among the 167 infants enrolled in the study, those who were moved in the middle of the night were even more likely to be placed in a sleep environment that posed hazards," the AAP said in a press release.

A 2014 study showed that more than half of American babies are still in danger from the threats posed by soft bedding. Researchers from the National Institutes of Health (NIH) and the Centers for Disease Control and Prevention analyzed data from nearly 20,000 parents. In 1993, almost seven out of eight parents used blankets or other soft bedding in their baby's cribs. Although those numbers dropped sharply over the years, by 2010, more than half were still in the habit. The study, which was published in the journal Pediatrics, found the practice was most common among young mothers, blacks and Hispanics.

The danger of loose bedding

Why the fuss over a blanket and pillow? Safety experts warn that soft bedding increases the risk for suffocation and SIDS. Accidental suffocation in bed is uncommon, but it is still the main cause of injury-related deaths in babies. The suffocation rate for infants doubled from 2000 to 2010, resulting in the loss of 640 babies. And while the number of SIDS deaths has been dropping, there were still 2,000 babies lost to SIDS in 2010.

In the cold winter months, put away the blanket. Instead, use a thicker one-piece sleep outfit (approved for use as infant sleepwear), and keep the room at a cozy temperature.

Editor's note: This story has been updated since it was originally published in December 2014.