Now parents are wondering whether they could be harming their own children by trying the age-old calming technique.
Nazila Sharaf, 35, and Lida Sharaf, 33, are facing three counts of felony child abuse and neglect and four counts of misdemeanor child abuse and neglect. The babies they had swaddled were seven months to one year old - well beyond the age for which swaddling is recommended. They also tied the blankets with what the police described as "heavy-duty knots" rather than simply tucking and folding the cloth around the babies, making it nearly impossible for the children to move their arms and legs. And they occasionally threw blankets over the children's faces after they were were swaddled, increasing their risk of suffocation, police said.
"They basically restrained these children, almost like a boa constrictor," Officer Steve Goard told the Contra Costa Times. "All of these children could have died in the process of binding these extremities."
Social services discovered the inappropriate swaddling, along with "multiple licensing violations," during an unannounced visit to the Universal Preschool day care center in Pleasanton, California, on March 12. (The center is now closed.) Doctors said that none of the children showed signs of injury from the alleged abuse, and a lawyer for the women - both of whom are pregnant and have older children of their own - says that they did not intend to hurt the babies.
"They are greatly embarrassed ... mortified by where they are," Timothy Rien, the Sharaf sisters' defense attorney, told the Contra Costa Times. "They are obviously shaken by the condition they're in."
Swaddling involves wrapping an infant snugly in a light blanket, mimicking the feeling of being in the womb. According to the American Association of Pediatrics (AAP), when done correctly swaddling can help calm babies and help them sleep better.
The trick is to keep the blanket taut but not too tight, to only swaddle infants who are young enough not to try to roll over by themselves.
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"I would stop swaddling by age two months, before they baby intentionally starts to try to roll," says Dr. Rachel Moon, the chair of the task force that wrote the AAP's safe sleep recommendations. Swaddled babies should sleep on their backs and be monitored to make sure they don't roll over by accident, because when they're swaddled, "the baby sleeps longer and doesn't wake up as easily," she explained in an article for the AAP.
The fact that they sleep so much more soundly is what makes many parents, and some child-safety organizations, nervous. In 2011, the National Resource Center on Child Health and Safety recommended against swaddling, saying that it "can increase the risk of serious health outcomes" like Sudden Infant Death Syndrome (SIDS). Their recommendation is part of the reason why it's illegal to swaddle babies in child care centers in Minnesota, and caregivers in Pennsylvania and California are increasingly urged not to do it.
"The difference in the advice for swaddling at home or the hospital nursery, versus in a child care center, really comes down to the age of the child and the setting," says Dr. Danette Glassy, chair of the AAP Section on Early Education and Child Care. "A newborn can be swaddled correctly and placed on his back in his crib at home, and it can help comfort and soothe him to sleep. When the child is older, in a new environment, with a different caregiver, he is learning to roll, and perhaps he hasn’t been swaddled before, swaddling becomes more challenging and risky."
But swaddling is practiced all around the world and has been for generations, pediatrician Dr. Harvey Karp, author of "The Happiest Baby Guide to Great Sleep" and a longtime swaddling advocate, told Yahoo! Shine. "Rather than banning swaddling in daycare, we should require that they learn how to do it correctly," he said.
"I compare swaddling to car seats," he continued. "Car seats are great, but only if you install them properly. If you install them incorrectly, they can actually cause problems."
When swaddling an infant, "You don't want to overheat the baby," he explained. "You don't want to wrap their heads or cover their faces. You don't want them swaddled on the stomach, and while you want their arms quite snug, you want their hips loose."
To swaddle an infant correctly, the AAP suggests that parents:
•Spread the blanket out flat, with one corner folded down.
•Lay the baby face-up on the blanket, with her head above the folded corner.
•Straighten her left arm, and wrap the left corner of the blanket over her body and tuck it between her right arm and the right side of her body.
•Then tuck the right arm down, and fold the right corner of the blanket over her body and under her left side.
•Fold or twist the bottom of the blanket loosely and tuck it under one side of the baby.
•Make sure her hips can move and that the blanket is not too tight.
Babies don't need to be swaddled constantly, Dr. Karp cautioned. "They only need swaddling during sleep and periods of upset," he told Yahoo! Shine. "The rest of the day they should have their hands out and be able to use their bodies." And he believes that swaddling, when done properly, decreases the risk of SIDS and suffocation rather than increases it.
"The benefit of swaddling is that it helps to reduce a baby's risk of rolling over," he explained. It also helps a baby feel more comfortable sleeping on its back, which means that mothers are more likely to follow recommended safe-sleeping practices. An unswaddled baby cries more, he said, "which then temps the mother to bring the baby into bed with her or put the baby to sleep on their stomach, which truly can increase a child's risk of death."