An analysis of babies lost to sudden infant death syndrome showed that swaddling increased the risk of death by a third, and the danger is greatest for babies sleeping on their stomachs.
While the lead researcher cautioned that more studies are needed, the evidence suggests parents shouldn't swaddle their babies after 4 months, The New York Times reported. And the study, published in the journal Pediatrics, said parents who choose to swaddle their newborns should be aware that the risk increases with the child's age.
Swaddling is an ancient practice in which the infant is wrapped tightly in cloth with the head exposed; the baby Jesus was wrapped in "swaddling clothes," the gospel of Luke says. Proponents say swaddling soothes the infant by making her feel safe since constraint mimics the close quarters of the womb.
Other studies have indicated that swaddling may help infants sleep better and can help to reduce pain.
For more than 20 years, the American Academy of Pediatrics has urged parents to put babies to sleep on their backs to reduce the risk of SIDS, which accounted for about 1,500 deaths in 2014, according to the Centers for Disease Control and Prevention.
“We already know that side and prone sleeping are unsafe for young babies, so the advice to place children on their backs for sleep is even more important when parents choose to swaddle them," lead author Anna Pease, of the University of Bristol in England, told Nicholas Bakalar of The Times.
“We suggest that parents think about what age they should stop swaddling. Babies start to roll over between four and six months, and that point may be the best time to stop," Pease said.
At The Atlantic, staff writer Adrienne LaFrance said parents shouldn't necessarily conclude that babies should never be swaddled, noting that nearly one-third of babies that died of SIDS were unswaddled and put to sleep on their backs.
Moreover, LaFrance said, technique varies widely, something that the authors acknowledged was one of the study's limitations.
"...As anyone who has tried to swaddle a baby can confirm, good swaddling takes practice. Many parents, for fear of too tightly wrapping their babies, end up swaddling too loosely, which is itself a suffocation hazard," she wrote, adding, "Some daycare centers in the United States don’t allow swaddling for this reason."
SIDS, which is most likely to occur between 2 and 4 months of age, is the leading cause of death for babies under 1 year old. Its incidence has steeply declined in the past quarter-century, however. There were 130.3 deaths per 100,000 babies in 1990 compared to 38.7 deaths per 100,000 in 2014.
The change is attributed in large part to a societal change in sleep position that has occurred through campaigns such as "Safe to Sleep." (Although another new study in Pediatrics suggests that teen mothers may be ignoring medical advice, leading to higher risk of SIDS.)
But although babies are better off sleeping on their backs, whether swaddled or not, they still need supervised time on their stomachs, medical professionals note.
The National Institutes of Health advise parents to place infants on their stomach two or three times a day. This "tummy time" will help prevent flat spots on the baby's head, improve motor skills and strengthen neck and head muscles.
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