Setting up your baby's sleep space: cot, mattress and room

A safe sleep space is simple: a cot or bassinet that meets your country's safety standard, a firm, flat mattress that fits it snugly, a fitted sheet and safe bedding, and nothing else. Put it in your room for at least the first 6 months, away from windows, cords and heaters. After that, comfort is about keeping the room dim at night, reasonably quiet and not too warm.

This guide covers the equipment and the room. For the rules that apply to every sleep (on the back, head uncovered, smoke-free, no sofa sleeping) see safe sleep. For outfits and tog, see dressing your baby for sleep.

What do you need for a safe sleep space?

Less than most shopping lists suggest. Red Nose's six recommendations describe the safest place for your baby to sleep as their own safe space, with a safe mattress and safe bedding.

Everything else, such as bumpers, pillows, sleep positioners and nests, is either unnecessary or unsafe. See sleep products to avoid.

How do I choose a safe cot?

Start with the safety standard. In Australia, Pregnancy, Birth and Baby says all new and second-hand cots must comply with the mandatory standard AS/NZS 2172:2003, and warns that not every cot sold meets it. In the US, the AAP's room checklist notes that standards now ban the manufacture and sale of drop-side cots. In the UK and elsewhere, look for a cot that meets the current national safety standard.

Then check the cot yourself with a tape measure. Pregnancy, Birth and Baby gives the Australian measurements, and the US Consumer Product Safety Commission (CPSC) and the AAP give the US ones:

The CPSC adds: no missing, loose or broken screws, brackets or other hardware, and no missing or cracked slats. Gaps matter because they can trap a baby's fingers, limbs or head.

Second-hand cots. A used cot can be fine, but it needs the same checks. Pregnancy, Birth and Baby says to use one only if all parts are in good working order and it comes with full instructions, and to check old cots for lead-based paint. Red Nose's safe environment page says second-hand cots under 10 years old should still meet safety standards, and that the base shouldn't sag. Search your national product safety website for recalls before using older gear.

What mattress should my baby's cot have?

Firm, flat and the right size. The Lullaby Trust's mattress advice says the safest mattresses are firm, flat and protected by a waterproof cover, with no raised or cushioned edges, and that your baby's head should sink no more than a few millimetres. Pregnancy, Birth and Baby says soft mattresses are dangerous because they become uneven as your baby gets heavier and raise the risk of suffocation and SUDI.

Check the fit:

• Australia: no more than 2 cm between mattress and cot side with the mattress centred, and no more than 4 cm when it's pushed to one side (Pregnancy, Birth and Baby).
• US: if you can fit more than two fingers between the mattress and the sides or ends of the cot, it doesn't fit (AAP).

Then:

1. Remove all plastic wrapping from a new mattress, which Pregnancy, Birth and Baby warns can suffocate a baby.
2. Never add a second mattress, a topper or extra padding. Red Nose says never to place additional mattresses or bedding in the sleep space.
3. Don't use a mattress that is damp, torn, mouldy or sagging, as Red Nose advises.
4. If you use a second-hand mattress, the Lullaby Trust says it should have a well-fitting, fully waterproof cover, no rips or water damage, and no sagging. It suggests a new mattress for each baby where possible.

Bedding on top. Use a fitted sheet made for the mattress, as the CPSC advises. Pregnancy, Birth and Baby suggests a sleeping bag with a fitted neck, armholes and no hood; if you use blankets, tuck them in firmly and no higher than your baby's chest, with your baby's feet at the bottom of the cot.

Bassinet, cot or portable cot: which should I use, and when?

Bassinet or Moses basket. Many families use one for the early weeks because it fits beside the bed. Red Nose's advice on rolling says to move your baby to a cot as soon as they first show signs of being able to roll, which for most babies is from about 4 months.

Cot. A cot can be used from birth, and your baby can sleep in it until they start trying to climb out. Pregnancy, Birth and Baby says to use the upper base height for younger babies who can't yet sit, pull up or stand, and the lower height for older babies so they can't fall or climb out. The AAP says to lower the mattress before your child learns to stand. The cot to bed transition covers the next step.

Portable cot. Pregnancy, Birth and Baby says portable cots are designed for temporary use, can be less safe than a permanent cot because they fold, and should meet the Australian standard based on AS/NZS 2195:1999. Set it up exactly as the instructions say, make sure it locks, use only the matching mattress (never a thick one or an extra layer, which could trap your baby against the stretchy side), and stop using it once your baby weighs 15 kg.

Twins. Pregnancy, Birth and Baby says each cot is made for one child, so separate cots are best for twins. See safe sleep for more on multiples.

Where should the cot go in the room?

In your room, for at least the first 6 months. Pregnancy, Birth and Baby says a baby under 6 months should have their cot in your room, and the NHS safer sleep advice says the same for every sleep, day and night. Moving your baby to their own room covers what comes after.

Within the room, Pregnancy, Birth and Baby, Red Nose and the AAP between them advise:

• Away from windows. The AAP says not to place a cot near a window.
• Away from cords. Keep curtains, blind cords and other cords out of reach; Red Nose calls them strangulation hazards. The AAP says no strings or cords should dangle in or near the cot, so keep baby monitor cables well away too.
• Away from heat and power. Keep the cot clear of heaters, power points, electrical appliances and lights.
• Nothing that can fall in. Avoid walls with pictures or mirrors above the cot, and keep mobiles and toys out of reach. The AAP says to remove a mobile once your baby can get up on hands and knees, or at 5 months, whichever comes first.
• Smoke alarms. The AAP advises a smoke alarm outside every room where someone sleeps.

Should the room be dark, quiet or a certain temperature?

Light. The NHS guide to helping your baby sleep suggests opening the curtains and getting on with normal activity by day, and keeping lights low, voices quiet and play to a minimum at night, so your baby gradually learns that night-time is for sleeping. A dim night light makes feeds and checks easier; the AAP says to keep it away from curtains and bedding. Many families also find a darker room helps daytime naps once their baby is a few months old.

Noise. You don't need silence, and the NHS says not to worry much about everyday noise during the day. If you use a white noise machine, keep it out of the cot and at a low volume. See white noise.

Temperature. Overheating is the concern, not a slightly cool room. The NHS suggests about 16–20°C. Red Nose doesn't recommend a specific room temperature, says a room thermometer isn't necessary, and suggests dressing your baby as you would dress yourself for the room. In hot weather a fan can help if it moves the air in the room rather than pointing at your baby. The NHS says your baby should never sleep with a hot water bottle or electric blanket, next to a heater or fire, or in direct sunlight. See dressing your baby for sleep and hot weather.

How do I check the setup with other caregivers?

Whoever puts your baby down should see the same setup. Walk through it together rather than assuming "the cot is ready" means the same thing to everyone:

• Which cot or bassinet are we using, and has it been put together following the instructions?
• Is it the mattress that came with or was made for this cot, with no extra layer?
• Has anything been put in the cot since the last sleep, such as a toy, muslin or blanket?
• Where does the cot sit, and is it clear of cords, heaters and windows?
• If we're away from home, does the portable cot have only its own mattress?

Recheck the setup whenever something changes: a new cot, a move to another room, a holiday or a growth spurt that means a bigger sleeping bag. Red Nose suggests calling ahead when you travel to check there's a cot or portable cot that meets Australian safety standards.

When to get help

Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) now if your baby is struggling to breathe, is grunting or sucking in their tummy with each breath, has blue, grey or blotchy skin or lips, is floppy or hard to wake, or is having a seizure. These are on the NHS list of when to get urgent help. Follow the call-taker's instructions.

Get advice the same day from your GP or a health advice line (Pregnancy, Birth and Baby on 1800 882 436 in Australia, NHS 111 in the UK, your pediatrician's after-hours line in the US) if you're worried about your baby after they've been caught in a gap in the cot or had a fall. The NHS says to get advice whenever you're worried about your child's symptoms or don't know what to do. If your baby is drowsy, floppy or hard to wake afterwards, call your local emergency number (000 in Australia, 999 in the UK, 911 in the US).

Talk to your GP or child-health nurse about breathing noises that worry you but aren't causing a struggle to breathe. The baby sleep sounds guide explains which noises are usually normal. Ask too if you've been told your baby needs a special sleep setup for a medical reason.

Report an unsafe product. If a cot, mattress or other sleep product seems faulty, stop using it and report it to your national product safety regulator. The CPSC links to a reporting service for US families.