Newborn parents may be doing something to their baby that could prove deadly, a new study claims.

New research claims that babies that are swaddled are a whopping 50 to 60 percent more likely to die of Sudden Infant Death Syndrome, or SIDS, according to a University of Bristol statement.

Swaddling is popular because it seems comforting to babies as it simulates conditions in the womb, and is widely practiced at hospitals. But the research suggests that swaddling is a lot more dangerous than we realize, especially when babies are not on their back.

The research found that the SIDS risk was higher in babies that are older, because they can more easily roll over onto their stomachs after being placed on their backs, which is why experts recommend that a baby over two months of age shouldn’t be swaddled. Also, tight swaddling may make the baby sleep too deeply.

Experts recommend that cribs be kept free of pillows or blankets to reduce the risk, and swaddle relatively loosely if you do at all.

“The focus of our review was not on studies about swaddling – a traditional practice of wrapping infants to promote calming and sleep – but on studies that looked at Sudden Infant Death Syndrome (SIDS),” lead author Dr Anna Pease, from the School of Social and Community Medicine, said in the statement. “We tried to gather evidence of whether there was an association between swaddling for sleep and SIDS. … We only found four studies and they were quite different, and none gave a precise definition for swaddling making it difficult to pool the results. We did find, however, that the risk of SIDS when placing infants on the side or front for sleep increased when infants were swaddled.”