The core of it
Six things carry most of the benefit:
- On the back, for every sleep — not the front, not the side, day and night.
- In a clear, flat, firm, separate sleep space — a cot, crib or Moses basket of their own.
- In the same room as a parent or carer, for every sleep, for at least the first six months.
- In a smoke-free environment, before and after birth.
- Head uncovered, and not too warm — a room between 16 and 20 degrees.
- Never asleep with an adult on a sofa or an armchair.
Everything below is detail on those six.
Sleeping on the back
This single change, promoted in the UK from the early 1990s, cut sudden infant deaths dramatically. Front sleeping was standard advice for a generation before that, which is why grandparents sometimes offer the opposite view in good faith.
No special equipment is needed and no wedge, pod or positioner should be used to hold a baby in place. Once a baby can roll from front to back unaided, there is no need to keep turning them over; they can be left to find their own position. Supervised tummy time while awake helps build the strength for that, and is worth doing from early on.
Babies who are swaddled must still be placed on their back, and swaddling should stop as soon as a baby shows signs of being able to roll.
The sleep space
A cot, crib or Moses basket with a firm, flat mattress, and nothing else in it. Specifically, out of the cot:
- Pillows and duvets
- Cot bumpers
- Soft toys
- Pods, nests and sleep positioners
- Weighted bedding and weighted sleeping bags
- Loose blankets that can ride up over the head
Sheets and thin blankets should be tucked in no higher than the shoulders, and the baby placed with their feet at the foot of the cot — the "feet to foot" position — so there is no room to wriggle downwards under the covers. A baby sleeping bag of the right size removes the problem altogether, and needs no additional bedding with it.
Nothing should be within reach of the cot either: blind and curtain cords, nappy sacks, cables and anything hanging are all hazards, and a baby's reach extends further each week.
Bouncy chairs and car seats are not sleep spaces. A baby who falls asleep in a car seat on a journey should be moved to a flat surface on arrival; prolonged sitting in a car seat allows the head to fall forwards and restrict the airway, and the risk is greatest in the smallest babies.
Sharing a room
A baby should sleep in the same room as an adult, for naps as well as at night, for at least the first six months. The reason is simply proximity: an adult in the room notices things.
No monitor replaces this. Movement monitors, breathing sensors and the various consumer devices sold on the promise of preventing sudden infant death have never been shown to do so, and a device that produces frequent false alarms tends to be switched off or ignored. A monitor is a convenience for hearing a baby from another room, not a safety system.
Temperature and overheating
Overheating is a risk factor, and babies lose heat mainly through the head and face, which is why covering the head matters. A room between 16 and 20 degrees suits most babies, and the chest or the back of the neck is a better guide to whether a baby is too warm than hands and feet, which are normally cool. Hats indoors should come off, and a baby brought in from outdoors in outer layers should be unwrapped rather than left to sleep in them.
Smoking
Smoking during pregnancy substantially raises the risk of sudden infant death, and so does exposure to smoke afterwards — at home, in the car, and anywhere else. This is one of the largest single risk factors, and it applies to anyone in the household, not only the mother. Free NHS stop-smoking support is available to pregnant women and to partners, and starting is worth it at any stage.
Smoking also changes the arithmetic of bed sharing, discussed below, from a manageable risk into a serious one.
Sharing a bed
This section needs to be read in full rather than skimmed, because the honest answer is neither "never" nor "it is fine".
Most parents share a bed with their baby at some point, whether they intended to or not — during a night feed, during an illness, or through sheer exhaustion. Guidance that simply forbids it tends to be ignored, and the dangerous version of bed sharing is the unplanned one, where nothing has been made ready. So the advice that matters is about circumstances.
It is dangerous to share a bed with a baby if any of the following apply:
- Anyone in the bed smokes, wherever they smoke
- Anyone in the bed has drunk alcohol
- Anyone in the bed has taken drugs, including prescribed or over-the-counter medicines that cause drowsiness
- The baby was born prematurely, before 37 weeks
- The baby weighed under 2.5 kg at birth
In any of those cases the baby should be put in a separate sleep space. Keeping a cot or basket alongside the bed makes that far easier at three in the morning than carrying a baby to another room.
Where none of those apply, and a parent decides to share a bed, the bed itself should be prepared:
- The baby on their back, not propped or on their side
- Adult pillows and duvet kept away from the baby
- No other children in the bed, and no pets
- No gap between the mattress and the wall, the headboard or a bedside table in which a baby could become wedged
- A slatted or decorated headboard dealt with, because heads fit into gaps
- No possibility of the baby rolling off, and never a baby left alone in an adult bed
Those checks need repeating as a baby becomes more mobile, since a bed that was safe for a newborn is not necessarily safe for a baby who can roll and push.
The claim that bed sharing protects against cot death
This appears in a good deal of older material and it is not supported. Bed sharing is associated with a raised risk of sudden infant death, and the raise becomes steep in the circumstances listed above.
The claim seems to be a garbled version of two findings that are real. Sharing a room is protective, and breastfeeding is associated with reduced risk. Neither of those is the same as sharing a bed, and conflating them has produced a confident piece of misinformation that circulates widely.
The reason UK guidance now explains how to share a bed more safely, rather than only warning against it, is that the risk turns out to be heavily concentrated in particular circumstances — and that parents who are going to do it anyway are better served by knowing which circumstances those are.
Sofas and armchairs
This is the one absolute rule in the whole of safer sleep advice. The risk of sudden infant death is around fifty times higher for a baby sleeping on a sofa or armchair with an adult than for a baby in a cot. Cushions, gaps down the side and the slope of the seat let a baby slide into a position from which they cannot breathe and cannot be seen.
Falling asleep on a sofa during a night feed is the classic circumstance, and it is why the practical advice is to feed in bed rather than on a sofa when there is any chance of dropping off: a bed that has been made ready is far safer than a sofa, and the alternative to a sofa is not staying awake, because nobody manages that reliably.
Dummies and slings
Research suggests that using a dummy for sleep may reduce the risk of sudden infant death, although the reason is not established and not all babies will take one. If a dummy is used, the advice is to wait until breastfeeding is established, at around four weeks, to offer it at every sleep rather than occasionally, never to force it, never to coat it in anything sweet, and never to attach it to a cord or clip around the neck. If it falls out once the baby is asleep there is no need to replace it. Stopping between six and twelve months avoids later problems with teeth and ear infections.
Slings and carriers have no established link to sudden infant death, but there have been deaths from airway obstruction in them, almost always in very young babies whose chin has dropped onto the chest or whose face has been pressed into the carrier's body or clothing. The TICKS rule covers it: tight; in view at all times; close enough to kiss; keep chin off the chest; supported back. Feeding a baby hands-free while walking about or doing something else is not safe; the baby should come out of the sling to feed.
Premature and small babies
Babies born before 37 weeks, and babies who weighed under 2.5 kg, are at greater risk and the guidance applies to them with less room for flexibility — in particular, bed sharing is not advised at all. Neonatal units give specific advice before discharge, and that advice takes precedence over anything general.
Where to get advice
Health visitors are the first point of contact for anything about infant sleep and will go through a household's particular circumstances rather than giving generic rules. The Lullaby Trust publishes the UK guidance in full and runs an information line. Anything that concerns breathing — pauses, noisy or laboured breathing, colour changes — needs medical assessment rather than a monitor, and a baby who is not breathing needs emergency help immediately.