Why is there so much conflicting advice about bringing your baby into bed?

Most parents share the bed with their baby during the night at one time or another

There's no convincing evidence that bedsharing increases the risk of Sudden Infant Death Syndrome (SIDS) or Sudden Unexplained Death in Infancy (SUDI), as long as you or your baby don't have special vulnerabilities. It's not the sharing of a sleep surface which increases risk. After all, human babies have been sharing a sleep surface with their mothers and parents for millenia. What matters is that you know how to share the bed as safely as possible.

A small number of breastfeeding babies and their parents have special vulnerabilities. Please check out if you and your baby fall into this more vulnerable group and what to do about it before reading further, by clicking here.

How does evolutionary biology help us?

It helps to think about baby sleep safety from the perspective of evolutionary biology. Human cultures are incredibly diverse, including in the way they care for their babies. However, there have been constants in the way babies are cared for in the night across diverse cultures throughout human history. As Homo sapiens, our tiny young ones are born with a biological or evolutionary drive to be close to the body of the mother, or a loving, nurturing adult.

In the night, for 300,000 years, Homo sapiens babies have

• Slept next to the bodies of their mothers or a loving adult

  • On firm, flat, bare sleep surfaces such as flat woven mats, or on thin surfaces which only slightly softened the floor or ground

  • With firm and low pillow arrangements for the adult's head, if used at all

• Exchanged a constant two-way stream of sensory information (for example, the sounds of breathing or of movement) with their mother or another loving adult who is close by

• Been responded to quickly (so that baby stayed dialled down and didn't wake others close by) with

  • Regular breastfeeds

  • Physical contact.

In contrast, contemporary sleep arrangements for baby often include

• Sleeping some distance from babies, even in another room using sleep monitors in which sensory information is exchanged only in one direction (baby to parent, not parent to baby)

• Sleep surfaces which contain

  • Lots of soft, puffy bedding

  • Soft, puffy pillows

  • Various soft toys and sleep aids

• Advice to the parent to delay responses, for fear of causing bad habits.

You can see from the perspective of evolutionary biology it's the cultural arrangements we make around sleep, not the act of sharing the bed, which are less safe for babies. This is confirmed by the latest sleep science. In fact, parents are able to change these cultural arrangements quite easily, once they know how.

Does it help to try and get rid of all risk?

The conflicting views amongst health professionals and various guidelines about whether or not it's safe to share your bed with your baby have come about because there are two quite different ways of thinking about safety and the wellbeing of a population of people, for example, mothers and babies.

The risk elimination approach to baby sleep safety

One is the 'try to get rid of all risk' approach. Researchers and health professionals in this camp, who are deeply committed to the well-being of families with babies, argue that if we know of anything that puts someone (for example, a mother and her baby) at even small risk of harm, we should very strongly advise her to change that behaviour. We might even feel we have to communicate to the mother that she is irresponsible in behaving that way (which does tend to shame her into doing as we ask). Interestingly, when we're trying to get rid of all risk, we're not really focussed on why she behaves that way.

But science tells us that trying to get rid of every small risk might accidentally bring other unexpected and unintended risks into our lives or our children's lives, instead. It's hard to say this, but the truth is that we can't get rid of all baby-sleep-related risk completely, whether your baby sleeps in a cot or in your bed. Any sleeping arrangement carries some risk of SIDS for our babies. This risk is very small though, once we put in place the big safer sleep strategies we've discussed.

One devastating consequence of the 'get rid of all risk' approach to baby sleep came about when exhausted parents began to sleep on their couches, lounges or sofas with their babies. They didn't want to put their precious little baby away from their body because when they did the baby woke up or cried. But they were beyond desperate for sleep and had been told not to share their bed with their baby. So they lay down on the couch. As a result, there was a terrible spike in the number of babies dying of SUDI.

The 'getting rid of all risk' approach risks triggering other problems.

The risk minimisation approach to baby sleep safety

The other approach could be called 'getting real about what people actually do, work out why, then help them weigh up what's important'. I belong to this latter camp, alongside a growing number of researchers and health professionals, who - needless to say - also care very much about the wellbeing of families with babies.

Actually, we can't eliminate all risk from our lives, nor from our babies' and children's lives, even though we might desperately want to. There are certainly some very big risks which are important to address. Babies are safest sleeping on their backs, for instance, and we need to make baby's sleeping place as safe as possible in other ways, too. There are some babies whose breathing needs special protection if they are sharing your bed.

But health systems such as in my own state of Queensland now have infant sleep safety guidelines which aim to minimise risk when our babies sleep, not eliminate it. Parents are given accurate and evidence-based information, then weigh up what they might like to do in their own unique situation.

This is, I believe, the way of the future in night-time baby-care. It's the approach we take in The Possums Sleep Program.

Acknowledgements

The photo at the top of this page is from the Baby Info Sleep Source basisonline.org.uk, taken by Rob Mank.

Recommended resources

The website Baby Sleep Information Source, by the Durham Infancy and Sleep Centre (DISC) UK, is the world's leading source of information and photographs for parents about safer infant sleep.

You might be interested in a podcast conversation I had with Professor Helen Ball, from DISC, in which we discuss sleeping babies safely available here.

Always put babies down to sleep on their backs (with a word about rolling and reflux, too)

How to keep the place where your baby sleeps as safe as possible

When your breastfeeding or breast milk feeding baby comes into bed with you

When your formula-feeding baby comes into bed with you

What about bedsharing when you have a baby whose breathing is more vulnerable?

How to keep your baby at the right temperature in the night

Wrapping or swaddling your baby: how to do it safely and does it help with sleep, anyway?

FAQs about safer baby sleep

Selected references

Ball H. Evolution-informed maternal-infant health. Nature Ecology and Evolution. 2017:DOI:10.1038/s41559-41017-40073.

Ball HL. Parent-infant bed-sharing behavior: effects of feeding type and presence of father. Human Nature. 2006;17(3):301-318.

Barry ES. Using complexity science to understand the role of co-sleeping (bedsharing) in mother-infant co-regulatory processes. Infant Behavior and Development 2022;67:101723.

Barry ES, McKenna JJ. Reasons mothers bedshare: a review of its effects on infant behavior and development. Infant Behavior and Development 2022;66:101684.

Bartick M, Young M, Louis-Jacques A, McKenna JJ, Ball HL. Bedsharing may partially explain the reduced risk of sleep-related death in breastfed infants. Frontiers in Pediatrics. 2022:doi:10.3389/fped.2022.1081028.

Bartick M. Study demonstrates why ABC recommendations must change. Pediatics. 2024;154(2):e2024-067288A.

Blair PS, Ball HL, Pease AS, Fleming PJ. Bed-sharing and SIDS: an evidence-based approach. Archives of Disease in Childhood. 2023;108(e6):doi:10.1136/archdischild-2021-323469.

Cole R, Young J, Kearney L, Thompson JM. Challenges parents encounter when implementing infant safe sleep advice. Acta Paediatrica. 2021;110:3083-3093.

Cole R, Young J, Kearney L, Thompson JM. Infant care practices, caregiver awareness of safe sleep advice and barriers to implementation: a scoping review. International Journal of Environmental Research and Public Health. 2022;19:7712.

Eatt J, Watson S, Ball H, Sevar K, Galbally M. Maternal depression and early parenting: a comparison between culturally and linguistically diverse and Australian born mothers. Australasian Psychiatry. 2022;30(1):119-125.

Grubb C, Young J, Downer T, D'Souza L. Beyond the rules: an integrative review of parental perspectives on safer infant sleep in shared environments. Frontiers in Public Health. 2025;13:https://doi.org/10.3389/fpubh.2025.1629678.

Marinelli KA, Ball HL, McKenna JJ, Blair PS. An integrated analysis of maternal-infant sleep, breastfeeding, and Sudden Infant Death Syndrome research supporting a balanced discourse. Journal of Human Lactation. 2019;35(3):510-520.

Mitchell EA, Thompson JM, Zuccollo J. The combination of bed sharing and maternal smoking leads to a greatly increased risk of sudden unexpected death in infancy: the New Zealand SUDI nationwide case control study. New Zealand Medical Journal. 2017;130:52-64.

Moon RY, Mindell J, Honaker S. The tension between AAP safe sleep guidelines and infant sleep. Pediatics. 2024;153(4)::e2023064675.

Rudzik AEF, Ball HL. Biologically normal sleep in the mother-infant dyad. American Journal of Human Biology. 2021;33(5):e23589

Zimmerman FJ, Bartick M, Feldman-Winter L, Ball HL. ABM Clinical Protocol #37: Physiological infant care - managing nighttime breastfeeding in young infants. Breastfeeding Medicine. 2023;18(3):159-168.