For the past two decades parents have been urged to place babies on their backs in hopes of reducing the prevalence of sudden infant death syndrome (SIDS), but many have not gotten the message.

The recent study also suggests healthcare providers have not worked hard enough to get the message out, an American Academy of Pediatrics news release reported.

Supine sleeping (being placed on the back to sleep) rates are as low as 50 percent in some U.S. regions. Across the country only about two-thirds of infants are placed on their backs to sleep.

"Given that supine sleep positioning significantly reduces an infant's risk for SIDS, it is worrisome that only two-thirds of full-term infants born in the U.S. are being placed back-to-sleep," lead author Sunah S. Hwang, MD, MPH, FAAP, a neonatologist at Boston Children's Hospital and South Shore Hospital, and instructor in pediatrics at Harvard Medical School, said in the news release. "More concerning is that adherence to safe sleep positioning is even lower for preterm infants who are at even greater risk for SIDS compared to term infants."

SIDS is the top cause of death in infants between the ages of one month and one year; over 2,000 died from the condition in 2010.

"Although the precise cause of SIDS is still unknown, we do know that safe sleep practices, such as sleeping on the back, reduces the risk of infant death in the first year of life," Dr. Hwang said. "The Back-to-Sleep campaign reduced the rate of SIDS by 50 percent in the 1990s. Since 2001, this rate has remained stagnant."

The researchers looked at data from a survey of the mothers of over 392,397; in the survey the subjects were asked if they put their infants to sleep " (side, back, stomach). Responses were categorized as supine (back) and non-supine, which included a combination of sleep positions," the news release reported.

The study found that both preterm and term infants had below ideal rates of supine sleep positioning after they were discharged from the hospital.

The rates varied from state to state;  "Alabama having the lowest rate at 50 percent and Wisconsin having the highest rate at 81 percent," the news release reported. They also found preterm infants were much less likely to sleep on their backs.

"Given the concerning data about inadequate adherence to safe sleep practices for all infants and in particular for preterm infants, we need to better engage families about adhering to safe sleep practices at the individual, community, hospital and public health levels," Dr. Hwang said.