How to Dress Your Baby for Sleep
A note on safety: The guidance in this article is intended as a general reference for parents of toddlers. Every child is different, and factors like illness, room ventilation, and individual temperature sensitivity can affect what's right for your little one. For babies under 12 months, always follow the safer sleep guidelines from The Lullaby Trust. If you have any concerns about your child's sleep environment or wellbeing, always speak to your GP or health visitor.
Here's a fact many new parents don't know: babies can't actually sweat properly for the first few weeks of life. Their sweat glands technically exist, but the mechanism that tells them to activate in response to heat is still coming online, which means a newborn has virtually no way of cooling themselves down if they're overdressed or in a warm room. They can't kick off covers, and they can't tell you anything at all. It's entirely up to the adults in the room to get it right.
This means that dressing a baby for sleep is one of the most consequential decisions you'll make as a new parent, with real safety implications if you get it wrong in either direction.
Why Getting This Right Matters So Much
Overheating in babies is one of the established environmental risk factors for Sudden Infant Death Syndrome (SIDS), and The Lullaby Trust is clear that keeping a baby cool and appropriately dressed is one of the most important things parents can do to reduce that risk. The right sleepwear therefore matters enormously: your baby can't regulate temperature the way you can, and the margin for error is smaller than with an older child.
What Should a Baby Wear to Sleep?
The simplest rule - and the one most reliably backed by both the NHS and general paediatric guidance - is to dress your baby in one more layer than you would wear yourself to feel comfortable in the same room. If you're wearing a T-shirt and sleeping under a light sheet, your baby needs a short-sleeve vest plus a light sleep bag. If you need pyjamas and a duvet, your baby needs a long-sleeve vest, a sleepsuit, and a slightly warmer sleep bag.
The layering should be simple and breathable. A cotton vest as the base layer, a cotton sleepsuit if the room is cooler, and a fitted sleep bag over the top. That's usually all a baby needs, and it gives you the flexibility to add or remove layers if the temperature shifts overnight.
Avoid anything with hoods, loose ribbons, or bulky fabric that could shift over the baby's face during the night. And never put a hat on a baby for sleep indoors. Babies release a significant amount of heat through their heads, and covering it interferes with their ability to cool down.
Why a Sleep Bag Is Usually the Safest Choice
Loose blankets aren't recommended for babies under 12 months because of the risk of them covering the baby's face or becoming tangled. A fitted sleep bag, sometimes called a wearable blanket, solves that problem by keeping the baby warm without any loose fabric that can move around.
Sleep bags come in tog ratings just like duvets, so you can match them to the season and the room temperature. A 2.5 tog sleep bag works for most UK winters when the bedroom is within the recommended 16-20°C range, while a 1.0 or 0.5 tog bag is better for warmer months.
The fit matters. A sleep bag should be snug around the neck and shoulders with properly sized arm holes, so the baby can't slip down inside it. Always check the weight guidance on the label, because a bag that's too big is a safety hazard.
How Do You Know if Your Baby Is Too Hot or Too Cold?
Forget the hands and feet. Babies naturally have cooler extremities because their circulation is still developing, so cold fingers don't mean they're cold overall. The most reliable check is to feel the back of the neck or the chest. The skin should feel dry, and not overly warm. If your baby feels hot, sweaty, or damp, they've got too much on and it's time to take something off.
Flushed cheeks, damp hair, or rapid breathing are also signs of overheating and should prompt an immediate adjustment. Restless sleep and frequent waking can be signs too, though these overlap with plenty of other causes, so don't assume temperature is the issue without checking first.
A nursery thermometer is genuinely useful. A baby's sleep environment can shift by several degrees between bedtime and the early hours of the morning without you noticing, and something as simple as a plug-in thermometer takes the guesswork out.
What About the Sleep Surface Itself?
Choosing the right mattress is as important as picking out your baby's outfits. Infants need a firm, flat surface for sleep, with no loose bedding to pose a risk. The mattress also needs to breathe, allowing air to circulate and preventing overheating.
Our Hybrid® Cot Bed Mattress is engineered with both safety and ventilation in mind. One side provides the firm, flat sleep surface that babies under a year old require, adhering to The Lullaby Trust's safer sleep recommendations. The other side is a softer toddler side, ready to use after your child turns one. It's certified to BS EN 16890, the UK safety standard for infant mattresses, and includes a water-resistant inner lining and a cover that can be machine-washed.
Put simply, a good night's sleep for your baby starts with the right mattress, suitable sleepwear, and a room that's cool and well-ventilated.
FAQs
Yes, in very warm weather, a baby can sleep in a nappy and a light sleep bag or even just a muslin cloth loosely laid over their chest. The priority in a heatwave is avoiding overheating, and it's safer to underdress than overdress.
Loose blankets aren't recommended for babies under 12 months due to the risk of suffocation. A fitted sleep bag is a safer alternative and provides the same warmth without the risks.
Babies can wear soft sleepsuits or pyjamas from birth as a base layer under a sleep bag. Traditional two-piece pyjamas tend to be introduced when children move out of sleep bags, usually around 18-24 months, though this varies.
Swaddling can help newborns settle, but it should stop as soon as your baby shows signs of rolling over, usually between two and four months. After that, swaddling increases the risk of SIDS and suffocation. Always follow current safer sleep guidance.
If the back of their neck or chest feels cool, add a layer under the sleep bag, such as a long-sleeve vest or sleepsuit. Don't add loose blankets or increase the room temperature significantly, as overheating is generally a greater risk than mild cool.
Important safety note:
This article offers general guidance on dressing your baby for sleep and is not a substitute for professional medical advice. Safer sleep recommendations can change, so always check the latest guidance from trusted sources before making decisions about your baby's sleep environment.
For up-to-date safer sleep advice, visit The Lullaby Trust and the NHS guide to reducing the risk of SIDS.
If you have been affected by the loss of a baby to SIDS, Sands (Stillbirth and Neonatal Death Charity) offers free, confidential bereavement support for families grieving after sudden infant death and other baby loss.
