Swaddling Helps Decrease Sudden Infant Death
Syndrome in Older Babies Too.

This study involved thirty-seven infants who were introduced to swaddling at an older age and examined babies' acceptance of sleeping on their backs. The research showed that the majority of infants accepted supine sleeping, including 78% who were used to sleeping prone (or tummy). The authors concluded that using swaddling and supine (or back) sleeping could promote a further reduction in Sudden Infant Death Syndrome.
Conclusion: It is never too late to swaddle. Even older babies can be helped to stay asleep on their backs when swaddled.

(Gerard, CM, Harris KA, Thach BT. Physiological Studies on Swaddling: An Ancient Childcare Practice which may Promote the Supine Position for Infant Sleep. Journal of Pediatrics. 2002; 141: 398-403)