The sudden and mysterious deaths of 40 to 50 infants in Minnesota each year might be categorized as “unexplained” in official records, but state health research has found a very explainable reason why they occurred: unsafe sleep environments.

The state Department of Health announced Wednesday that 82% of the sudden unexplained infant deaths reported in the state in 2016 and 2017 were related to sleeping (74 out of 90 total deaths). Most involved babies who were placed to sleep on surfaces other than cribs, or with loose bedding or fluffy blankets or toys that present suffocation hazards.

Six in 10 involved infants sleeping on their sides or bellies, even though the American Academy of Pediatrics recommends that infants sleep on their backs.

New parents generally get the right safety information from doctors, surveys show, but the death numbers suggest that some parents misunderstand the message or get mixed signals from friends or relatives, or from retailers selling hazardous crib products, said Dr. Courtney Jordan Baechler, assistant commissioner for the Health Department.

“It’s going to take all of us and it’s going to take the community to change the standard” around safe sleep practices, she said.

Overall, the number of sudden unexplained infant death (SUID) cases in Minnesota appears stable. The state recorded 58 in 2016, 32 in 2017 and 51 in 2018. The deaths are separate from those with clear reasons, such as car crashes. For 2018, the number of SUIDs linked to unsafe sleep environments was not yet available due to the time required to investigate them.

The Hennepin County Medical Examiner’s Office reviewed 23 SUIDs in the county in 2018 and found 14 related to unsafe sleep positions — usually parents sleeping with the infants on their beds, often with soft pillows or blankets.

Most babies won’t die if placed in these risky positions, said Dr. Owen Middleton, Hennepin’s assistant chief medical examiner, “but if you are the parent or parents of an infant who dies as a result of an unsafe sleeping environment, it is a devastating experience, especially if these deaths can be prevented.”

Determining sleep-related causes of SUIDs can take weeks to months and often requires a “doll re-enactment” in which county investigators ask parents to recreate how they placed their children to sleep and how they found them after they died.

“Incredible information comes from these re-enactments,” Middleton said, but they are difficult for the parents and investigators.

At an infant safety event on Wednesday, state health officials lauded the efforts of local hospitals and providers such as Hennepin Healthcare, which received national certification for its level of staff training and parent education on safe sleep requirements.

One source of the problem can be that parents don’t emphasize the importance of safe sleep practices when leaving their infants with relatives or licensed or unlicensed child care providers, said Jennette Flynn, a clinical supervisor of inpatient pediatrics at Hennepin Healthcare. The state Health Department didn’t have a breakdown of where the sleep-related deaths occurred in recent years.

State human services officials cracked down on unsafe sleep environments in licensed family child care facilities five years ago after a spike in deaths. The Legislature also enacted changes, including requiring a doctor’s note for licensed care providers to place infants in sleep positions other than on their backs, in cribs, and without loose blankets. The number of deaths in day care dropped sharply after those rules took effect.