Dressing infants for colder months

Stine Smith

Managing Director of Roots & Wings

Even for older babies, winter can be potentially hazardous to their health – unless the parents dress them adequately – because their body’s ability to regulate its temperature is far less efficient than adults.

The best way for babies to avoid convection heat loss is being in what is termed a ‘thermally neutral environment’ – a nursery/household temperature of between 17°C – 22°C. This is especially important when transferring a newborn from birth to postnatal care facilities (or home) within 24 hours of birth – full-term newborns are rarely able to shiver (to warm their bodies up). This makes them extremely vulnerable to heat-loss, even from simply breathing in cool air.

So, if your baby needs to leave the warmth of a hospital maternity ward, then do remember to pre-warm the car’s interior before putting baby into it to drive anywhere!

At home, fan heaters tend to produce ‘dry’ air, and gas heaters tend to produce ‘wet’ air. So, our personal favourite heaters for maintaining an ambient newborn environment are electric oil-filled heaters or heat pumps with their automatic thermostatic temperature controls. If there is a heater in baby’s room, leave the door ajar so it doesn’t get too hot and there is sufficient air flow.

Newborns are vulnerable, thermally-challenged human beings

As soon as your baby is born, they go from having spent the previous nine months in water of 37°–38° degrees (the equivalent of a lovely hot spa pool), to suddenly breathing in air that is typically in the low 20s.

The drastic change in temperature often shocks them into a first inhale – which is a good thing – but from that second on, they can instantly begin to lose heat through radiation. On top of that, brand new babies are wet, so they rapidly lose body-core heat through evaporation.

Then, if the towels and blankets used to dry and wrap them are not pre-warmed, baby will also lose body-heat through conduction (by touching cold items – including their mother’s cold skin if she has been in a chilly C-section theatre).

Young babies have a large surface-to-mass ratio. This means that, in comparison to adults, they have three times the amount of skin to potentially lose heat from (mainly their head) in relation to their small body mass that needs to produce heat – so they rapidly lose heat to the environment.

In fact, a newborn’s “heat-loss area” (their head) is one-quarter of their body – in comparison to us adults whose heads are just one-tenth of our body. Most babies have little or no hair, which means a newborn without a hat is the equivalent of adults being nude to our nipple-line, with our heads shaved. Brrrrrr.

A new baby’s skin doesn’t have the layers of fat under it like we do to keep the body warm, which is why newborns looks ruddy-red – it is because their skin is thinner.

Additionally, it is normal during the first few days for a newborn to lose up to 10 percent of their birth weight … so they become even more vulnerable to cold-stress over their first couple of weeks.

In young babies, signs of hypothermia (low body temperature) include rosy cheeks and lethargy, which can easily be mistaken for a bonny contented sleepy baby. But what is actually happening is their metabolism has escalated requiring, increased oxygen and glucose to step up their heat production. If the situation continues for hours or days, these babies can struggle to feed well, and potentially fail to thrive – often with loving, caring, devoted parents who just have no idea their newborn is simply cold.

The real question ends up being not “which newborns are cold-stressed?” but “what newborns manage to maintain an ideal core body temp despite so many odds against them?” According to the World Health Organisation one of the most important steps in keeping newborns warm is appropriate clothing.

As a midwife on birthing suite, Kathy Fray has seen many parents bringing inappropriate clothing for their newborn, especially not enough layers, ill-fitting hats, synthetic fibres, and poorly-sized outfits the baby ‘swims’ in.

So, what is appropriate clothing for a newborn?

Correct sized clothing that provides a perfectly snug fit for a day one baby.

“Newborn”-sized clothing is actually designed to fit a baby for one to three month olds, and optimally at around four to eight weeks when baby’s have typically gained one to two kilos and grown several cm in height. What fits a newborn is very different to what fits a thriving two-month-old. Babies do not stay the same size for three months!

Recommendation: Invest in your newborn having the correct size clothing to wear on their birth-day and for their first one to three weeks of life – and don’t believe that the label “newborn” means it is suitable for a day one baby – most aren’t.

Correct natural fibres that actively work to support baby’s core temperature

The cute designer garment you received at your baby shower may not be the best choice for your day one baby to wear next to their skin. It might be perfect by six to eight weeks of age, when baby is over five weeks and over five kilos, but not on their birth-day.

Also, babies spill feeds and leak moisture outside their nappies, so synthetics and cotton will leave your baby wet and cold. You need a fibre that keeps your baby warm even when damp and will push the moisture away to evaporate into the air.

Recommendation: Invest in your newborn being surrounded in natural wool fibre. Merino, especially, has proven to be the best amongst wool fibres due to its unique features. The fibres are a lot finer than normal wool, which means it’s far smoother against the skin (not itchy or scratchy). These fine, but durable, fibres actively work with your baby’s skin to protect them and keep them warm, even when wet.

Properly fitted merino hat

Unless it is warm during summertime and your baby has been born with a big mop of hair, newborns should wear a good-quality, well-fitting, soft stretchy merino woollen hat at all times.

Recommendation: A soft merino beanie, designed specifically for brand new babies, is ideal – and it’s critically important the beanie fits snuggly around the head, so it doesn’t easily fall off, or slip and cover baby’s eyes, nose or mouth.

Does it really make a difference what fabric or fibre I use for my baby?

Heck yes! And it can be a jungle to navigate what is best for your vulnerable wee newborn, and your older baby as he or she grows.

Merino outperforms all other fibres when it comes to looking after your baby:

Benefits needed by babiesMerino Wool“Normal” Sheep WoolCottonSynthetics
Soft against the skinXXX
Temperature regulatingXX
Moisture control – absorbs and evaporates any spills leaving baby warm and dryXXX
Fire resistantXX
UV protectingXXX
“Whiff” resistant – spills will not smell as badX
Self-cleansing – so you can relax on the washingXX
Proven to improve baby contentmentX (1)
Improved sleepX (2)
Reduces risk of SUDIX (3)
Reduces allergiesXX
Easy to washXXX
Natural stretch and elasticity for movement and comfortXXX
Best for autumn useXXX
Best for winter useXX
Best for spring use

1 – At the Cambridge Maternity Hospital in 1979, Scott and Richards found that low-birthweight babies gained an extra 10g a day compared to babies that weren’t on Merino
2 – 1979, Scott and Richards also found that babies sleeping on Merino settled more quickly, cried less and fed for longer periods. Parents of infants who were sleeping on Merino also
reported a stronger sense of parent-baby bonding.
3 – One cause of SIDS is overheating in babies. Merino temperature regulates much better than any other fibre and will work with your baby to keep at the best temperature.

We are lucky in New Zealand to have magical merino wool grown right here. For many countries in Europe and in the States, people can’t believe how it ticks all their boxes of what they want in a fabric. Once they try our wonder-wool they get hooked. Merino is the absolute best for newborns, babies, toddlers and children.

Not all merino is equal

Have you ever wondered why some merino is so much cheaper than others? As it turns out, it may not be the cheapest solution long-term, or even the healthiest for your baby. Merino is made from the protein keratin, just like our hair and nails. You may have noticed that in periods of stress or not eating or sleeping well, your nails tend to break frequently, and your hair loses its shine. The same goes for wool fibres.

Many sheep-farming countries engage in controversial mulesing (removing folds of skin from the tail area of a sheep) and chemical dips, which work well for the farmer’s profit but not for the quality of the wool. This type of farming allows cheaper Merino to enter the market, but with low quality fibres that also have been soaked in chemicals. This results in garments that will quickly fall out of shape when washed, then turn thin and scratchy, not providing the benefits that you would expect.

However, when the sheep live under healthy conditions, with clean nature, good grass, and little disturbance from humans, it directly shows in their wool fibres. They are more elastic, don’t break easily, and have a natural shine. New Zealand merino sheep have the great advantage of living in our country with an abundance of space and natural food, and where procedures like mulesing and chemical dips are illegal. So, you are more likely to get high quality merino when you choose NZ wool.

Remember, if the merino wool garment price-tag is cheaper than you expected, then chances are it won’t be the quality you expected either.

What should my baby wear over the cooler months?

Keeping babies warm during winter is critical, for the repercussions of a hypothermic baby can be serious. However, a baby’s age also impacts on the strategies of warmth required. Babies really fall into three categories:

Neonate (newborn, zero to six weeks old)

Regarding air temperature and newborns, our best advice is to think of a baby as thermally-challenged, because although newborns have a little natural protection against the cold, they are not able to protect themselves against the side effects of inhaling low air temperatures. Newborns need a consistently warm room temperature of 17°–22°C for the first month or so, until baby’s body has started to fill out with improved levels of insulating fat.

Non-mobile baby (non-crawler, one to nine months old)

The golden rule with non-mobile babies is always one extra layer than an adult. So, if say you have a t-shirt and sweatshirt, then your baby needs a singlet, onesie and done-up cardy; or if your bed needs one blanket, then your baby needs two. Also, non-crawlers in cool air consistently need a hat; and in cold air they need a thicker hat covering their ears, plus booties and perhaps mittens.

Mobile baby (crawling, eight to twelve months)

The use of skeletal muscle for the actions of crawling metabolically creates body heat, so these infants can be dressed similarly to an adult, with the added precaution of a hat to maintain heat – unless they have a big mop of hair and the temperature is warm.

For chilly air temperatures, a great investment for all infants is thermal singlets, available as a vest or body-suit, and short- or long-sleeved. These are great at keeping an infant’s torso (and vital organs) warm. When out and about in winter using the pram or stroller, then great warmth extras include a sheepskin liner, carseat-pram snuggler-bag, and a storm rain-cover.

A word of caution to expectant parents

It is vital to be vigilant regarding air temperatures if transferring after childbirth from a hospital to postnatal care facility or transferring from the birth facility straight home. Hours-old babies are extremely vulnerable to rapid heat loss, even if dressed well.

Practical hints and tips

  • Multiple thin layers are better than one thick layer – because warmth gets trapped like insulation between the layers.
  • Dress your baby in at least two base layers of good quality merino.
  • Add your “fashion statement” for your baby on top of the two base-layers.
  • When you take baby out of the home, make sure they wear a well-fitted thin merino wool beanie.
  • A common misunderstanding is that it’s best for baby to have a cotton singlet or top layer next to skin. This was true back in the day of itchy woollen jumpers, however, we now know that soft wool is the best fibre we can put next to skin, and we have superfine soft merino.
As a general rule, use your common sense; if you’re feeling cold, your baby will be too. Babies don’t have the ability to regulate their temperature as we do, and by checking between baby’s shoulder blades you’ll be able to determine if you need to add or remove a layer. If it feels clammy, baby is too hot, if cool to touch, add a layer.

When you’re making up a warm and cosy bed for your baby, always remember to consider all safety aspects to reduce the risk of SUDI. For full information on keeping babies safe in bed refer to and the Ministry of Health

Liz Pearce, Operations Manager, Parents Centre Aotearoa

What bedding should you use?

The same rules apply at bedtime. Ensure the cot is draught free; lightly pre-warm the cot mattress with a wheatie-bag or similar; ensure the room’s air temperature is thermally-neutral and will stay that way overnight, and use one to two more bedding layers than you would need yourself. After the newborn phase, sleep-bags can be ideal replacements to a sheet and/or blanket.

Lightweight layers of blankets can be added to the cot when your baby is sleeping. You can easily add or remove the blankets as needed. They must be large enough in size so they can be tucked in under the cot mattress. Natural fibres such as merino, cotton or bamboo work best – you do not want your baby to overheat in a synthetic blanket.

Your baby should sleep, at the bottom of the cot. So, when you make the bed, ensure the sheets can only reach as far as your baby’s chest, and tuck the sheets and blankets well under the mattress. That way if your baby moves during sleep their head will not get covered by the sheets.

What about bath time?

Air temperature is especially important when a baby is wet because they are then vulnerable to rapid heat loss through evaporation of water from the skin. A good rule of thumb at baby bath time, is a bath water temperature of about 37°; use pre-warmed towels; always dry baby’s head first; then after drying their body replacing the wet towels with dry towels.

What if you have to go out on a cold day?

When it comes to going out to the shops or for a stroll in the pram after five or six weeks of age, on a cool day an infant generally requires at least a woollen long-sleeve singlet, woollen long-sleeved stretch’n’grow onesie, booties, cardy and woollen hat (ensuring the nape of their neck is also kept warm). On a cold day, baby also typically needs a thick jacket, mittens, and shawl-wrap. And on a windy day – well, baby needs to stay at home!

If the pram is forward-facing, as most modern prams are, then a windbreak pram-cover is recommended. Backward-facing prams (when parent and baby can look at each other) can be gentler on young babies, though less interesting for a toddler. Another ‘must’ in the pram in winter is a buggy-liner comfort-insert or sleeping-bag cocoon. And remember, even if your baby is a busy mobile crawling machine, when they are strapped into a pram, they still need one more extra layer than you, because their body isn’t making heat by walking.

What if you’re worrying baby is too warm?

It is equally as important not to overheat babies, for infants are poorly equipped to cope with hyperthermia (high body temperature). The normal adult hyperthermic response to reduce a high core temperature is to remove some clothing, and sweating – but babies can do neither.

Young babies tolerate a very limited range of temperatures – so as parents we all need to be vigilant of our baby’s temperature. If you’re ever unsure, then check their temperature. In young babies especially, ideally you want to aim for high 36s or low 37s°C.

Older siblings need looking after too

A baby’s reactions to its surroundings is considerably more visible than older children’s. This doesn’t mean older children don’t have the same needs, but their bodies are simply better at absorbing the harm caused by an inappropriate fibre.

Toddlers or preschoolers move around a lot more. There is a lot of running involved in little people’s lives, and a lot of stopping to explore their surroundings. This is the way they learn and grow.

They need to keep warm and dry when involved in outside play. They are often not aware of the fact they need to put on a jumper, and in school they will most likely never put on a jacket unless forced to.

  • Always put a layer of merino underneath the t-shirt. This keeps them warm, dry and protected.
  • If you’re taking your older children into the snow, put them in merino top and leggings. You don’t have to wash it, it doesn’t smell, it absorbs moisture created during exercise, and there’s no itch for them to complain about.



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