Parents are often told to swaddle their newborn babies in order to help them sleep, but a new analysis of studies finds that the practice may increase the risk of SIDS, the New York Times reports. Researchers looked at four studies that examined a total of 760 cases of sudden infant death syndrome, and found that swaddling (wrapping a baby tightly in a blanket in order to simulate the feeling of being in the womb, AOL reports) increased the risk for SIDS by about a third overall. Of the babies who died of SIDS, 17% were swaddled. The biggest risk was in babies asleep on their stomachs. It was less risky for those sleeping on their sides, and the least risky for those sleeping on their backs.
Swaddling makes it more difficult for a baby to move, so a baby on his stomach may be more at risk if he is swaddled and his face is pushed into the mattress. The current recommendation is for parents to place babies on their backs to sleep, and the researchers say this is even more important if the baby is swaddled. The researchers also found the risk increased as the age of the babies increased, and as the study notes, it was greatest for babies older than six months—"babies start to roll over between four and six months, and that point may be the best time to stop" swaddling, the lead author says. As for babies swaddled and then put to sleep on their backs, researchers did find a "small but significant risk" of SIDS, the Atlantic reports, and that's likely related to babies who were put to sleep on their backs swaddled, but then rolled over.