How To Put A Crying Baby To Sleep, The Scientific Way | CNN

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It’s every parent’s nightmare – an exhausted baby who won’t stop crying when it’s time to go to bed. Even worse? The baby finally falls asleep in your arms but wakes up again and starts sobbing when lying in the crib.

The solution is a magic pair of numbers – five and eight – according to Japanese researchers who experimented with 21 mothers trying to put their babies to sleep.

Here’s how it works: Walk your baby around for at least five minutes without jerking around, by which time the little one will be calm or even sleepy, according to the study. Then sit and hold the baby for another eight minutes before gently transferring to the crib.

According to study co-author Dr. Kumi Kuroda, team leader of the Affiliative Social Behavior Unit at the RIKEN Center for Brain Science in Saitama, Japan, placing the sleeping baby in the bed without first sitting quietly for a full eight minutes ended in disappointment.

“Although we did not predict it, the key parameter for successful elongation of sleeping infants was the (delay) of sleep onset,” Kuroda said in a statement.

“I raised four children and performed these experiments, but even I couldn’t predict the key results of this study until the statistical data became available,” Kuroda added.

The timing guidelines might be helpful for some parents and caregivers, but won’t necessarily work for everyone, said Atlanta pediatrician Dr. Jennifer Shu, medical editor of the American Academy of Pediatrics.

“Babies are different and (some) might not all respond to this system,” said Shu, who was not involved in the study.

Parents and caregivers shouldn’t use this technique regularly if a baby can fall asleep on their own, added Shu, who is also the co-author of “Heading Home With Your Newborn: From Birth to Reality.”

“The goal should be to ensure that baby sleeps well using this or other techniques while eventually encouraging him to fall asleep on his own, both at the start of bedtime and throughout the night (when he wakes up),” Shu said in an email.

The study, published Tuesday in the journal Current Biology, examined the impact of four soothing behaviors on infant crying. Mothers were asked to carry their baby while walking, to walk with their baby in a stroller or “mobile bed”, to hold their baby in a sitting position, and finally to put their baby directly into a crib or bed. The researchers monitored the baby’s heartbeat and filmed each session to record and time the response.

According to the study, sitting and holding a crying baby didn’t work – monitors showed the baby’s heart rate increased and the behavior continued. Unsurprisingly, putting the crying baby directly into the crib didn’t work either.

Only movement calmed the babies, according to the study. In five minutes, all babies carried by walking mothers stopped crying, heart rate slowed and 46% of infants slept. According to the study, an additional 18% of babies fell asleep within a few extra minutes.

However, the five-minute walk only resulted in sleep for crying babies. “Surprisingly, this effect was absent when the babies were already calm before,” Kuroda said.

Researchers found similar results when parents pushed babies in strollers, but the impacts weren’t as robust.

Now for the even harder part: putting sleeping babies to sleep without waking them up. A third of the babies in the study woke up immediately after being put to bed, no matter how gently. But it wasn’t the touch of the bed on a baby’s body that woke them up, the study found. Instead, the monitors showed that the baby’s heart rate response accelerated when the baby was first detached from the mother’s body.

However, when the babies were restrained for an additional eight minutes, they entered a more stable state of sleep – a state that did not waver when they separated from their mother, the researchers found.

Human babies, like other mammals, react to what’s called the “carrying response,” an innate response seen in species whose babies are too immature at birth to walk or care for themselves.

We see it all the time in nature videos: mother lions, tigers and other wild cats, as well as their domesticated cousins, carry their babies by the scruff of their necks. The same is true for wild and domestic dogs, mice and rats. Great apes, monkeys, and other primates carry their babies on their backs, where the babies settle and cling, as do opossums and giant anteaters. Marsupials like kangaroos, koalas, and wallabies all have specialized pouches for cradling their babies as they grow.

The answer seems instantaneous – once mom picks up the baby and starts moving, the infant is relatively docile and their heart rate slows, according to research by Kuroda and his team.

Unfortunately, it seems humans aren’t as lucky as other mammalian mothers and have to carry their young longer to get the same response. There’s another thing that sets people apart – the need for human babies to learn to sleep on their own.

“Holding or fully rocking a baby to sleep creates a routine that the baby will learn to expect,” Shu said. “When the baby wakes up in the middle of the night in a light sleep phase (as we all do), he may need to repeat the routine.”

For babies 4 months and older, the AAP recommends putting them to bed when they are drowsy instead of waiting until they are completely asleep.

And don’t rush to soothe a baby over 3 months old when they wake up, recommends the AAP. Just like adults, the baby can squirm, fuss and fall back to sleep very well.

Be sure to follow safe sleeping guidelines: You should always put babies on their backs for naps and at night, in an approved crib without bumpers, pillows, stuffed animals, duvets, comforters, or blankets.