In 1994, the "Back to Sleep" campaign launched, urging American parents to put their babies to sleep on their backs to reduce the risk of sudden infant death syndrome, CBS News reports.

According to News Medical, rates of infants sleeping on their back increased from 10 percent to 78 percent over the next 10 years, and the rate of SIDS dropped by 53 percent.

But a study published Monday in Pediatrics revealed back-sleeping findings that one neonatologist calls "depressing" and "frustrating." The study of nearly 3,300 new mothers found only 43.7 percent both intended to put their babies to sleep on their backs every time and actually followed through on that, CNN reports.

The study also found 77.3 percent of mothers "usually" put their babies to sleep on their backs, but not "exclusively." Experts say sleeping on their stomachs can be more dangerous for infants who aren't accustomed to it.

People who didn't put their babies to sleep on their backs were most often afraid the baby would choke or wouldn't be as comfortable. Doctors say those beliefs could be due to lack of education or familial pressure.

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The study found that mothers who had family members advocate for stomach-sleeping were more than 12 times more likely to put their babies to bed on their tummies.

There were at least 1,600 deaths from SIDS in 2015. (This baby was said to have died of SIDS; 38 years later, an arrest was made.)

This article originally appeared on Newser: Moms Still Put Babies to Sleep in Unsafe Positions