Babies may sleep better by snuggling with a parent in bed, but the practice puts the child at greater risk for death, according to a new study that found such “unsafe sleep practices” the biggest factor behind infant deaths.

Accidental suffocation is the leading cause of death among babies under 1 year old in the United States, with 82% percent of these tragedies occurring in a bed, according to a study published Monday in the journal, Pediatrics.

“Understanding the circumstances surrounding these deaths may inform prevention strategies,” the study said.

Fourteen percent of all sudden unexpected infant death cases from 2011-2104 were classified as suffocation. The remaining cases were classified as “unexplained.” Soft bedding accounted for the greatest number of suffocation deaths (69%), followed by overlay (19%) and wedging (12%).

Researchers found two common characteristics in all three categories: the infants fell asleep on their stomach or side, and they slept in an adult bed.

“Unintentional injury deaths, such as those categorized as suffocation in our study, can be prevented by following infant safe sleep practices,” the report’s authors stressed in their report. “The safest place for infants to sleep is on their backs, on an unshared sleep surface, in a crib or bassinet in the caregivers’ room, and without soft bedding (eg, blankets, pillows, and other soft objects) in their sleep area.”

About half of all the soft bedding cases occurred in an adult bed, while 27 percent happened in a crib or bassinet. In nearly all of the cases, the babies were found asleep in on their stomachs or side. Most of the cases involved the baby one or more blankets blocking the baby’s airway. The median age of death in these cases was 3 months.

Seventy-one percent of overlay suffocations also occurred in an adult bed, with half of the infants found on their stomach or side. Most overlay deaths were “attributed to neck or chest compression,” rather than the obstruction of the infant’s nose and mouth. The median age of death was 2 months.

Wedging occurs when a baby is trapped between inanimate objects. Forty-five of these cases involved sharing a sleep surface — most of the time in an adult bed in which the infant was stuck between a mattress and wall, or between a mattress and bed frame. The median age of death in these cases was 6 months.

Rates for accidental suffocation and strangulation in bed have increased from 6 deaths for every 100,000 live births in 1999, to 23 deaths in 2015.