Creating a Safe Sleep Environment for Your Baby: What to Get Right
This article offers general information and isn't a substitute for professional advice. Always follow current NHS and Lullaby Trust safer-sleep guidance, and speak to your health visitor or GP with any questions about your baby's sleep.
The safest cot is the barest one. That single idea runs against almost everything the baby aisle sells you, and it's something worth holding onto when you're standing in a shop looking at padded bumpers and shaped positioners.
Safer-sleep guidance has been refined over decades of research, and it comes down to a small number of principles about the surface, the space and the room. What follows is general information, and you should always follow current NHS and Lullaby Trust guidance and ask your health visitor about anything specific to your baby.
A Firm and Flat Sleeping Surface
Everything rests on the sleep surface. Guidance is consistent that a baby sleeps on a firm, flat mattress, because a soft or sagging surface that lets the head sink in is a recognised risk. Press it with your palm. It should feel firm and spring straight back rather than moulding round your hand and holding the shape. It's the opposite of what we design an adult mattress to do, and that contrast catches a lot of parents out.
Flat matters as much as firm. No raised sections, no contouring, no cushioned areas, and nothing soft added on top. Every instinct you have says a baby would be more comfortable on something softer, and this is one of the few times in parenting where the instinct is simply wrong. Firm is the safe surface, and it's the first thing to get right because nothing else compensates for it.
The Two-Finger Test
A mattress has to fit its cot with no meaningful gaps. The usual guide is that you shouldn't be able to fit more than about two fingers between the mattress and any side of the cot, because a wider gap is a space a baby can become wedged in.
Measure the inside of your cot before you buy rather than trusting that a standard size will fit, because cots vary more than you'd expect. Too small leaves gaps, too large won't lie flat, and neither is acceptable. Check the mattress condition while you're there: firm throughout, no dips, no damage, no staining that won't clean off, and a waterproof cover that's fully intact.
What Goes In, and What Stays Out
The cot needs a firm mattress, a fitted sheet, and your baby. That's the list. No pillows, no duvets, no bumpers, no positioners or wedges, no soft toys for young babies. Each of those can obstruct breathing or cause overheating, which is why guidance keeps them out rather than merely advising caution.
Pillows and duvets aren't recommended below twelve months. For warmth, use light blankets tucked in firmly at chest level, or a baby sleeping bag in the correct size, because neither can ride up over the face. A cot dressed this way looks bare next to the nursery photographs online. The bareness is the safety feature.
Temperature, Position and the Room
Overheating is a recognised risk factor, so aim for a room that's comfortably cool rather than warm, generally cited as around 16°C to 20°C. Use a room thermometer instead of judging by how it feels to you, since adults and babies experience the same room differently. Keep the cot away from radiators, heaters and direct sun, and dress your baby in layers you can add or remove.
Position is fixed: on the back, for every sleep, day and night, with feet at the foot of the cot so they can't wriggle down beneath the covers. Keep blind cords, cables and curtains out of reach. Guidance is also for your baby to sleep in your room for the first six months, naps included, which is worth planning for when you're working out where the cot goes.
Second-Hand Mattresses
This is where we'd be most cautious. Some research has suggested a possible link between used cot mattresses and increased sleep risk, so a lot of parents buy new for each baby purely to remove the uncertainty, and we think that's a reasonable instinct.
If you are reusing one, it needs to be firm and flat, undamaged, with a completely intact waterproof cover, cleaned and stored dry, and a snug fit in the cot you're using it in. If any one of those is in question, replace it. There are plenty of places to economise with a new baby and this isn't one of them.
Keep It Boring, and Keep It Consistent
A striking amount of what's marketed for baby sleep consists of things guidance would have you leave out of the cot. Sleep positioners, bumpers, pillows, padded accessories. The safest setup is also the plainest, which is not a message the market has much incentive to push.
Consistency does the rest. The same rules apply to daytime naps as to nights, and wherever your baby sleeps, at home, at a grandparent's, on holiday. It's easier to apply one standard everywhere than to make judgement calls when you're tired.
The Stage After the Cot
Cots are outgrown sooner than most parents expect, usually somewhere between two and three years, and then the requirements change. Your child needs a mattress sized for a child's bed and built for a child's weight, not the cot mattress and not a hand-me-down adult one.
For that stage, we’d recommend our children's mattress for their first proper bed: it’s a single built to a shallower 16cm depth, which is what raised and bunk beds require so the guard rail still sits high enough above the sleeping surface.
FAQs
A firm, flat mattress that fits the cot snugly, a fitted sheet, and nothing else. Baby on their back with feet at the foot of the cot, in a room that's comfortably cool at around 16°C to 20°C, and in your room for the first six months.
Pillows, duvets, cot bumpers, sleep positioners, wedges and soft toys, for young babies. All of them can obstruct breathing or cause overheating. Use firmly tucked light blankets or a correctly sized baby sleeping bag for warmth instead.
Firm enough to spring straight back when you press it, with no soft give that moulds around your hand. A surface that lets the head sink in is a recognised risk, which is why guidance asks for firm and flat rather than soft and cushioned.
Comfortably cool, usually given as 16°C to 20°C, and worth checking with a thermometer rather than judging by feel. Overheating is a recognised risk factor, so keep the cot clear of radiators and direct sun and dress your baby in adjustable layers.
Guidance urges caution, since some research suggests a possible link between used cot mattresses and raised risk.
This article offers general information and isn't a substitute for professional advice. Always follow current NHS and Lullaby Trust safer-sleep guidance, and speak to your health visitor or GP with any questions about your baby's sleep.
