Can My Baby Sleep in a Hat?

The answer, and who says it

The Lullaby Trust's guidance on dressing a baby for sleep contains the sentence directly: "Hats should be removed indoors. Babies lose heat through their heads, so if their heads are covered, the baby can overheat. Take off any hats when your baby is indoors."

Red Nose Australia builds the same point into its framework. Keeping a baby's head and face uncovered is the second of its six safe sleep recommendations, on the grounds that "babies control their temperature through their face and head, so keeping baby's face and head uncovered during sleep helps reduce the risk of overheating". It also says it helps keep their airway clear, which reduces the risk of suffocation.

Two bodies, two countries, the same answer. This is not a topic where UK and Australian advice diverges.

Why a hat is different from a jumper

The reasoning is physiological rather than a general dislike of layers. A baby's head is a large proportion of their body surface and it is how they shed heat. Cover it and you remove the route they use to cool down, which is the mechanism behind the warning. The Lullaby Trust states elsewhere that the risk of sudden infant death syndrome is higher in babies who get too hot, and that research shows babies are safer being cooler than being too hot.

The second reason is the airway. Red Nose's guidance on covered heads lists what happens when a baby's face or head is covered: it can block or restrict the airway, cause rebreathing of the same air with rising carbon dioxide and falling oxygen, lead to overheating, and increase the risk of suffocation, smothering or asphyxia. A hat that slips down over the face during sleep does exactly that, and a baby under a year cannot reliably move it.

The other things that count as head coverings

Red Nose names them: hats, hoodies, bonnets and headbands. It also flags hazards such as ribbons and loose fabric, which can create strangulation or entrapment risks. Add to that the ones parents do not think of — a swaddle brought up over the head, a muslin draped over a pram, a sleeping bag with a hood, a blanket pulled above chest level.

The Lullaby Trust's clear-cot advice covers the rest of the space: no pillows or duvets, no cot bumpers, no soft toys, no loose bedding, no pods or nests, and nothing that keeps a baby in one position. The safest cot for a baby under one is close to empty, and that includes what is on their head.

The hospital hat, and outdoors

Newborns are often given a hat at birth, and hats outdoors in cold weather are ordinary and sensible. Neither contradicts the advice, because the advice is specifically about sleep indoors. The Lullaby Trust's rule is framed around being indoors: take the hat off when your baby is inside. When you come in from a walk, that includes the moment your baby is still asleep in the pram in the hallway — that is exactly when hats get forgotten and babies overheat.

If your baby is in hospital, follow the unit's instructions. Premature babies are sometimes kept warm with head covering under continuous clinical observation, which is a different situation from a baby asleep in a cot at home. The Lullaby Trust's advice for premature babies at home is to follow safer sleep guidance for 12 months from the due date rather than the birth date.

What to do instead when the room is cold

The Lullaby Trust publishes the alternative. When it is cooler than 16C, add an extra layer of clothing or choose a higher tog sleeping bag if your baby feels cold. If you are using a baby sleeping bag, do not add extra blankets on top of it. Do not double up sleeping bags either — the Lullaby Trust warns that two 1.0 tog bags do not make 2.0 tog, because air trapped between the layers increases the warmth further, and that this could increase the risk of SIDS.

Then check the baby rather than the thermostat. Feel their chest or the back of their neck. Hands and feet are normally cooler and are not a guide. If the skin is hot or sweaty, remove a layer.

What about a cold nursery in winter

The recommended room temperature is 16 to 20C, and a room thermometer is the cheapest thing in this whole subject. If your room genuinely will not reach 16C, the fix is heating, insulation, moving the cot away from a draughty window, and more clothing or a higher tog bag — not a hat, and not a duvet. If cost is the barrier, say so to your health visitor: the Lullaby Trust can point families to baby banks, which supply cots, mattresses and bedding free of charge.

What to do if the hat keeps reappearing

Hats are the classic gift, and they are also the classic thing a well-meaning relative puts back on while you are out of the room. The Lullaby Trust publishes guidance specifically for other carers and babysitters, which exists because advice has changed over the decades and grandparents in particular may be working from what they were told at the time. Its framing is useful in conversation: this is not a preference, it is one of a short list of measures, and doing things differently from the baby's usual routine is itself named as something that can increase risk. Sent in advance, it is easier than a discussion in a hallway.

When to ask

Speak to your health visitor or public health nurse if you cannot keep the room within a reasonable range, if your baby always feels cold to you despite layers, or if you are unsure what your baby should wear at a given temperature. Get urgent advice if your baby is hot, sweaty, floppy, unusually hard to wake, or has a temperature of 38C or above under three months.