Throughout most of human history, newborn babies slept in close contact with their mothers. When that wasn't possible, somebody else held them while mom took a break. But nowadays, if you visit a hospital maternity ward, you'll find newborn babies left to sleep in little plastic boxes.
How does that affect the baby? That’s the question posed by Barak Morgan and colleagues of the University of Cape Town in the Journal of Biological Psychiatry.
The researchers studied 19 normal, full-term, caesarean-born babies in the maternity ward. As is typical in many places, these South African babies stayed with their mothers in the hospital for 3 days after birth. When they slept, the infants were loosely swaddled and kept in open bassinets alongside their mothers’ beds.
But on Day 2, the babies contributed some data for science. They were fitted with chest electrodes and monitored while they slept in two, one-hour sessions. For one session, the babies slept in the bassinet. For the other, the infants slept – skin-to-skin – on their mothers’ chests.
The researchers measured heart rate variability – an indicator of activity in the autonomic nervous system. In general, a more active autonomic nervous system means you are more alert, tense, or “revved up.” So the researchers reasoned that a sleeping baby experiencing increased autonomic activity is more stressed.
After each baby had been tested under both conditions, the researchers compared the results.
And the difference was marked.
Overall, babies experienced a 176% increase in autonomic activity when they slept alone in the bassinet. They also got less “quiet sleep,” which is the newborn equivalent of REM sleep in adults.
Why? The difference wasn’t attributable to body temperature. Babies might have been warmer when they slept on their mothers. But warmth, say the authors, tends to boost autonomic activity. So if anything, body heat should increase autonomic activity – not decrease it.
On the other hand, we know that skin-to-skin contact has therapeutic effects. In experiments on preterm infants, babies who get more skin-to-skin contact have experienced better health and faster brain maturation.
In one study, the preemies who got skin-to-skin contact immediately after birth ended up with optimal cardiovascular stability 6 hours later. Among babies who were randomly assigned to the incubator, less than half displayed cardiovascular stability. The researchers of that study concluded: “Newborns should not be separated from their mothers.”
Getting back to the South African research, Barak Morgan and colleagues warn that their study was small, and needs to be followed up by a study that measures infants’ stress hormone levels. But meanwhile, we seem to have evidence that is consistent with everyday experience and intuition—and what we know about human evolution. Babies are better off when they in close contact with their caregivers.
But wait a minute. What about safety? What about SIDS? Are these researchers advocating that mothers sleep with their newborns? Isn’t that dangerous?
I don’t think anybody’s trying to persuade adults to fall asleep with their babies on their chests. But concerns about SIDS and accidental smothering have led public health officials to promote slogans like “Babies sleep safest alone.”
It’s a misleading slogan. Yes, the typical Western-style bed is not a safe place for babies to sleep. Babies who sleep with caregivers who are exhausted, intoxicated, or drugged are at special risk. And nobody should fall asleep with a baby on a chair, sofa, or soft surface with loose bedding.
But babies are not safer when left alone in a room. And I’ve yet to see a study that compared health outcomes of infants who slept in cribs with health outcomes of infants who slept alongside their mothers under the sort of conditions that were once common in traditional Japan (discussed here). Maybe – even under stringent safety conditions – babies are still at a small risk. I don’t know.
But more to the point, we need to consider both sides of the equation. Very likely, most Westerners are not interested in making the changes needed to create a low-risk bed-sharing environment for their babies. So they should probably stick with a crib. But does that mean we ignore the downside – a baby who gets less tactile comfort from its parents?
Virtually every choice has its costs and benefits. Leaving baby to sleep in a box – beyond the reach of a loving parent – is probably no exception. That doesn't mean we have to give up the box. But understanding the costs of the box might inspire us to discover helpful compromises, like more skin-to-skin contact time. And being open-minded will surely help us learn more about our babies. And ourselves.
If you're interested in the original study, see Morgan BE, Horn AR, Bergman NJ. 2011. Should neonates sleep alone? Biol Psychiatry. 70(9):817-25. Epub 2011 Jul 29.
For my analysis of the research on infant bed sharing, "Bed sharing with infants: Can it be done safely?"
And for critical review of the way public health officials have handled co-sleeping recommendations, check check out "Never Sleep with Baby? Or Keep Me Close But Keep Me Safe: Eliminating Inappropriate "Safe Infant Sleep" Rhetoric in the United States by Lee Gettler and James J. McKenna, a paper you can download by clicking here.
Opinions expressed by parent contributors are their own.