The safest way to dress a newborn for sleep is in fitted layers of clothing, with or without a wearable blanket (sleep sack), and no loose blankets, hats, or heavy coverings. The general rule is one more layer than what you’d comfortably wear in the same room. Getting this right matters because overheating is a known risk factor for sudden infant death syndrome (SIDS), while underdressing can leave your baby too cold to sleep well.
The One-Extra-Layer Rule
The NHS recommends giving your baby one extra layer of clothing compared to what you’re wearing. If you’re comfortable in a t-shirt and sweater, dress your baby in a bodysuit, sleepsuit, and a light cardigan or sleep sack. If the room feels chilly to you, your baby likely feels it too.
This rule works because newborns can’t regulate their body temperature the way adults can. They lose heat quickly through their heads and extremities, but they also overheat easily since they can’t kick off covers or pull at their clothes. Layering lets you add or remove a piece without a full outfit change at 2 a.m.
What to Wear at Each Room Temperature
The ideal nursery temperature is between 61°F and 68°F (16°C to 20°C), according to the Lullaby Trust. Keeping the room in this range helps lower SIDS risk. If you use a sleep sack, its warmth is measured in TOG (Thermal Overall Grade) ratings. Higher TOG means warmer.
Here’s a practical breakdown:
- 75°F and above (24°C+): A diaper only, or a short-sleeve bodysuit with a very lightweight sleep sack (0.2 to 0.5 TOG).
- 72°F to 75°F (22°C to 24°C): A short-sleeve bodysuit with a light sleep sack (0.5 to 1.0 TOG).
- 68°F to 72°F (20°C to 22°C): A long-sleeve bodysuit or lightweight pajamas with a 1.0 TOG sleep sack.
- 64°F to 68°F (18°C to 20°C): A long-sleeve bodysuit plus footie pajamas with a 2.0 to 2.5 TOG sleep sack.
- Below 64°F (below 18°C): A warm base layer under heavier pajamas with a 2.5 to 3.5 TOG sleep sack. Consider warming the room rather than adding more clothing.
In hot weather, it’s perfectly fine for your baby to sleep in just a short-sleeve bodysuit or even a diaper alone. Don’t feel pressured to always use a sleep sack if the room is warm.
Sleep Sacks Over Loose Blankets
The American Academy of Pediatrics is clear on this: keep blankets, quilts, comforters, and nonfitted sheets out of your baby’s sleep area. Airway obstruction from soft objects or loose bedding is the most common cause of accidental infant suffocation. A wearable blanket is the recommended alternative. It keeps your baby warm without the risk of fabric riding up over their face or bunching around their head.
Weighted sleep sacks, weighted blankets, and weighted swaddles are not considered safe and should not be used.
Swaddling: When It’s Safe and When to Stop
Swaddling can help soothe newborns by dampening the startle reflex, but it’s not a strategy that reduces SIDS risk. If you do swaddle, always place your baby on their back.
The critical rule is that swaddling must stop as soon as your baby shows any signs of trying to roll. A swaddled baby who rolls onto their stomach has no way to push themselves back or free their airway. Most babies start showing early rolling signs between 3 and 4 months, though some do earlier. Signs to watch for include pushing up on their hands during tummy time, attempting to twist their body when unswaddled, fighting the swaddle when you put it on, or trying to get their hands up near their face while wrapped.
Between 4 and 6 months, the startle reflex naturally fades, which removes the main reason for swaddling in the first place. By 6 months, most babies should be sleeping fully arms-out. If your baby has outgrown the startle reflex but hasn’t started rolling yet, that’s still a good signal to transition to a sleep sack with arms free.
Skip the Hat Indoors
Once you’re home from the hospital, don’t put a hat on your baby for indoor sleep. Hats trap heat and can slide down over a baby’s face. The AAP advises against indoor hat use beyond the first hours of life, since the risk of overheating outweighs any benefit for temperature maintenance in a normal home environment.
Choosing the Right Fabric
Breathability matters more than thickness. Cotton is the classic choice for baby sleepwear: it’s natural, breathable, and durable, though it doesn’t wick moisture especially well. Bamboo fabric has become popular because it’s softer, naturally temperature-regulating, and pulls moisture away from skin, which helps if your baby tends to get sweaty. It’s typically a bit more expensive.
Avoid polyester when possible. It traps heat and sweat, and the seams can be rougher against sensitive skin. Wool is warm but tends to be scratchy and harder to wash, making it impractical for everyday baby sleepwear. Whatever fabric you choose, look for snug-fitting pajamas without drawstrings, ties, or loose decorations that could pose a hazard.
How to Check If Your Baby Is Too Hot or Cold
The best spot to check is the back of your baby’s neck or their chest. Hands and feet tend to run cooler naturally in newborns, so they’re not reliable indicators. If their neck or chest feels hot, sweaty, or clammy, they’re overdressed. If the skin feels cool to the touch, add a layer.
Signs of overheating include flushed or red skin, damp hair, fussiness, restlessness, or unusual sluggishness. Some babies develop heat rash, which looks like tiny red bumps in skin folds, around the neck, or on the bottom. A normal baby temperature is around 97.5°F (36.4°C). Keep in mind that babies can be overheated without visibly sweating, so touch-checking is important even if they don’t look damp.
When in doubt, err slightly on the cooler side. A baby who’s a little cold will fuss and wake you up. Overheating is a greater safety concern and harder for a sleeping baby to signal.