Placing your baby on their back for every sleep is the single most effective SIDS prevention measure. Here's the evidence and what to do when they start rolling.
Of all the safe sleep practices, sleep position has the strongest and most consistent evidence behind it. Putting your baby on their back to sleep — for every sleep, every nap — is the single most impactful thing you can do to reduce SIDS risk.1
The Back to Sleep campaign: what changed
In 1992, the AAP first formally recommended that infants be placed on their backs to sleep.1 In 1994, the NICHD launched the "Back to Sleep" public health campaign across the US.2 Similar campaigns followed in the UK and Australia.
The results were stark. In the decade after the campaign launched, SIDS rates in the US fell by more than 50%.2 In the UK, deaths fell from over 1,500 a year in the early 1990s to around 200 today.3 This is one of the largest reductions in infant mortality achieved by a single behavioural change.
The campaign's name has since been updated to "Safe to Sleep" to reflect the full range of safe sleep guidance, but the back-to-sleep position remains its foundation.2
Why supine is safer
Two biological mechanisms explain why prone (front) sleeping increases SIDS risk.
Airway position. When a baby sleeps on their front, the chin drops forward and the soft tissue of the posterior pharynx can partially obstruct the airway. On their back, the airway is more naturally open.
Arousal thresholds. Prone sleeping is associated with deeper sleep and a reduced ability to rouse in response to low oxygen levels. The ability to wake up and signal distress is a key protective mechanism against SIDS — one that infants in the early months are still developing. Prone sleep suppresses this mechanism at exactly the age when it matters most.1
Always back to sleep — every sleep, every nap, every caregiver. The risk applies to naps as much as nighttime sleep.
Side sleeping is not safe
Side sleeping is sometimes presented as a middle ground between prone and supine. It isn't. Babies placed on their side can roll to their front, and the risk associated with accidental prone positioning is the same as intentional prone positioning.1 The AAP is clear: only the back is recommended for sleep.
What happens when baby starts rolling?
Once your baby develops the ability to roll from back to front and front to back consistently — typically around 4–6 months — the calculus changes slightly.
The AAP guidance: continue to place your baby on their back at the start of every sleep. If they roll to their preferred position during sleep, it is not necessary to reposition them throughout the night.1 By the time babies can roll both ways, their muscle strength and motor control have developed to a point where the risk associated with prone positioning has substantially fallen.
Before your baby can roll both ways: always back, actively repositioned if they move.
Do not use wedges, sleep positioners, or rolled towels to keep your baby on their back after they start rolling. These objects are themselves SIDS and suffocation hazards.
Tummy time is not sleep time
Tummy time — placing a baby on their front while awake and supervised — is important for development. It builds the neck and core strength that leads to rolling, sitting, and eventually crawling. It also reduces the risk of flat spots developing on the back of the head (positional plagiocephaly).
Tummy time and sleep position are completely separate things.
Tummy time: awake, supervised, on a firm floor surface, for short periods (start with 2–3 minutes a few times a day, build from there).
Sleep position: always on the back, always unsupervised (by definition, since you'll be sleeping).
Never leave a baby in a prone position and go to sleep yourself. The risk only exists when supervision ends.
The practical rule for every caregiver
The value of back-to-sleep depends on consistency. One caregiving session where a baby is placed prone on a soft surface is enough for the risk to apply. Make sure everyone who cares for your baby knows the rule:
- Always on their back
- On a firm, flat surface
- No exceptions for "just this once" or "they sleep so much better on their tummy"
The fact that a baby appears to sleep more deeply on their front is not a reason to do it — deeper prone sleep is part of the mechanism of risk, not evidence of safety.
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Also in this cluster: Room sharing · What to put in the cot
Sources
- American Academy of Pediatrics. "Sleep-Related Infant Deaths: Updated 2022 Recommendations for Reducing Infant Deaths in the Sleep Environment." Pediatrics 150(1), 2022. https://publications.aap.org/pediatrics/article/150/1/e2022057990/188304/Sleep-Related-Infant-Deaths-Updated-2022-Recommendations
- NICHD Safe to Sleep. "About the Safe to Sleep Campaign." National Institute of Child Health and Human Development, 2024. https://safetosleep.nichd.nih.gov/
- The Lullaby Trust. "Safer Sleep Advice." 2024. https://www.lullabytrust.org.uk/safer-sleep-advice/
Footnotes
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American Academy of Pediatrics. "Sleep-Related Infant Deaths: Updated 2022 Recommendations for Reducing Infant Deaths in the Sleep Environment." Pediatrics 150(1), 2022. https://publications.aap.org/pediatrics/article/150/1/e2022057990/188304/Sleep-Related-Infant-Deaths-Updated-2022-Recommendations ↩ ↩2 ↩3 ↩4 ↩5
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NICHD Safe to Sleep. "About the Safe to Sleep Campaign." National Institute of Child Health and Human Development, 2024. https://safetosleep.nichd.nih.gov/ ↩ ↩2 ↩3
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The Lullaby Trust. "Safer Sleep Advice." 2024. https://www.lullabytrust.org.uk/safer-sleep-advice/ ↩