Never let me go

Should newborns sleep alone? Those that do may sleep less and experience stress, Ed Yong reports.

As soon as babies are born, mothers hold them close in loving cuddles. But in Western countries, that contact soon disappears. Newborn infants spend nights in the plastic boxes of maternity wards or in their own individual cots back home. And this separation might cause problems for them. Barak Morgan from the University of Cape Town has found that babies who sleep alone show signs of stress and sleep less soundly.

Neonate in an incubator

In a study published in November in Biological Psychiatry, Morgan used electrode pads to eavesdrop on the heartbeats of 16 two-day-old infants as they spent an hour sleeping alone in a bassinet and an hour sleeping skin-to-skin in their mothers’ embrace. He measured the variation in the gaps between the babies’ heartbeats.

When we are stressed, our autonomic nervous system becomes more active, our hearts beat faster, and the gaps between those beats become more variable. That’s exactly what Morgan saw in the infants who slept alone. They had 176% more variability in their heartbeats than infants who had skin contact with their mothers, suggesting that that they were more easily stressed. They also got just 14% of the quiet sleep that their peers did.

Quiet sleep is important for developing brains. But Morgan doesn’t know if babies would still experience the same dramatic difference in sleep quality after days of sleeping alone, or what the long-term effects of such differences would be. Monkey studies provide a clue: they have repeatedly found that newborns become distressed if they sleep apart from their mother, have higher levels of stress hormones, and behave unusually. They have also shown that these problems persist in the long-term.

Currently, the American Academy of Pediatrics (AAP) advises mothers to sleep in the same room as their babies, but in different beds. For now, it’s too early to say if this advice should be changed. On the one hand, sleeping alone has some clear short-term drawbacks. And throughout our evolutionary history, mothers would have slept in close physical contact with their babies. On the other hand, sleeping together with an infant increases the risk of ‘cot death’, or Sudden Infant Death Syndrome (SIDS) – hence the AAP’s advice.
For now, Morgan himself says that his results should be treated with caution. He wants to repeat a longer version of his experiment, as well as measure the babies’ levels of stress hormones such as cortisol.

This study is really intriguing because it explores an unknown territory,” says F1000 Faculty Member Donatella Marazziti from the University of Pisa. She notes,

the study underlines the importance of maternal-neonatal skin-to-skin contacts, which is increasingly recommended in neonatal units.

Morgan’s study supports this move.

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Filed under Developmental Biology, Psychiatry.

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