When your formula-feeding baby comes into bed with you

Sudden Infant Death Syndrome (SIDS) and Sudden Unexpected Death in Infancy (SUDI) can be hard to talk about, because the thought of any precious little baby dying is distressing. But some things are important to know. You can find out why putting babies down to sleep on their backs matters so much here, how to keep baby's sleep places as safe as possible here, and how to avoid baby overheating here.

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.

Many parents bring their baby into bed because it makes the nights easier and they get more sleep

Having your baby close to your body, on the same sleep surface, is often the easiest way to meet your baby's evolutionary needs for close physical contact in the night. This is as true of babies who are fed with formula, as it is of breastfed babies.

If we look inside the homes of families with babies at night (as researchers have done), we see great variability in sleeping arrangements, which change throughout the night, and from night to night, in response to family members' changing needs.

Often babies start the night in their side-cars or bassinets or cots, for instance, and end up in the parental bed. A parent feeling under pressure to perform in paid work the next day might disappear into another room for some uninterrupted sleep. Or one parent spends much of the night in bed with an older child, while the other cares for the baby. This is what is real in the night for twenty-first century families with babies and toddlers.

Quite often, parents who are not planning to share their bed with their baby end up doing so at some point in time anyway. This is why all parents have the right to know how to bedshare as safely as possible, just in case.

What does the research tell us about sharing your bed with your baby who is mostly or wholly formula feeding?

There's never been convincing evidence that bedsharing in itself increases the risk of SIDS or SUDI, as long as the family has no special vulnerability. Yet parents of babies in advanced economies, particularly in the English-speaking world, have been exposed to decades of well-meaning public health campaigns against bedsharing. It is, however, important to know how to make any surface your baby sleeps on, including in your bed, as safe as possible. You can read more here, here, and here.

You might have heard that it's unsafe to bring your baby into your bed at nights if your baby is predominantly formula fed. This belief isn't evidence-based. There is no research which proves an increased risk of SUID or SIDS when formula fed babies share the bed with their parents, compared to when breastfed babies share the bed with their parents.

If you plan to bring your formula-feeding baby into bed with you, or if you find that you do sometimes in the night anyway because it's easier and you're exhausted, then in my view this is a biologically normal and reasonable thing to do.

However, there are two things which are important to know from the research when you're sharing your bed with your precious little baby, whose feeds are mostly or wholly of formula.

1. A video study found that women whose baby had never breastfed were less likely to adopt a cuddle curl or C-shaped position with their bodies when their baby was bedsharing. Breastfeeding women who had the baby in bed with them typically took up this position, which is thought to help protect baby from airway accidents in the night.

It makes sense, then, if you are bringing your formula fed baby into bed with you, to be sure you place him on his back with his head level with your breast or chest, rather than up higher in the bed near your face, where pillows might block off his breathing. You can read more about this position, with a photo of parents adopting it, here.

2. Formula fed babies have also been shown to be less easily roused during active sleep, which could make it harder for them to respond if their breathing is threatened.

What matters, if you are bringing your formula fed baby into bed with you, is that you sleep baby on her back (more here) and make sure that your bed is as safe as possible (more here and here). These are the same precautions which apply when your formula fed baby is sleeping in a side-car, bassinet or cot.

There's no research proving that

• Sleeping baby between two parents increases the risk of SIDS or SUDI

• A parent who is very tired or a heavy sleeper puts baby at increased risk of SIDS or SUDI when bedsharing

• An overweight parent increases baby's risk of SIDS or SUDI when bedsharing.

You can find more about these three things here.

Do you find you don't sleep well with baby in the bed?

Sometimes you mightn't be sleeping well with your baby in bed because you've been worrying about your baby's safety, given all the frightening (though often inaccurate) messages you might have heard. Parents often relax into much better sleep once they receive the latest, evidence-based information about sharing a sleep surface.

Here are two ideas which can make the nights work better when a family decides to bedshare. You could experiment with

• Putting your mattress on the floor. This deals with the problem of a dangerous edge for baby to fall over

• Making sure there is plenty of space in the bed for yourself, baby and any other adult or child who might join you. This might mean bringing another mattress into the room to lie up snug alongside your existing one, if your bedroom is big enough.

However, there are plenty of parents who find they don't sleep very well with the baby in bed, regardless, or who make a choice never to bedshare, preferring to use the side-car crib, bassinet, or cot.

My job is to provide you with the facts as best we know them, so that you can weigh things up and make your own decisions, experimenting to see what works best for you and your baby, in your own unique situation.

Acknowledgements

The images on this page are from the Baby Info Sleep Source basisonline.org.uk, and were 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, about sleeping babies safely 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

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?

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

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.

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.

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.