A newborn sleeps best in one more layer than you’d wear comfortably in the same room. In practice, that usually means a onesie or footed pajama paired with a swaddle or sleep sack, with no loose blankets, hats, or extra bedding in the crib. The exact combination depends on your room temperature, which is the single most important factor in choosing sleepwear.
Start With Room Temperature
Most pediatric sources recommend keeping your baby’s room between 68°F and 72°F (20°C to 22°C). The AAP hasn’t set a precise number because overheating risk depends on more than air temperature alone, including what your baby is wearing, humidity, and airflow. But that 68–72°F range is a reliable target for most homes.
If you don’t have a nursery thermometer, a simple indoor thermometer near the crib works fine. Knowing the actual temperature takes the guesswork out of choosing layers.
What to Dress Your Baby In
Here’s how layering works at different temperature ranges:
- 75°F and above: A short-sleeved onesie or just a diaper with a lightweight (0.2 TOG) sleep sack is enough.
- 71°F to 74°F: A cotton footed pajama with no extra layers, or a onesie with a 1.0 TOG sleep sack.
- 68°F to 70°F: A cotton or fleece footed pajama with a 1.0 to 2.5 TOG sleep sack works well.
- Below 64°F: Add a long-sleeved onesie under footed pajamas and use a 2.5 to 3.5 TOG sleep sack.
TOG is a rating that measures how warm a fabric is. The higher the number, the more insulation it provides. Most sleep sacks list their TOG rating on the packaging, so matching it to your room temperature is straightforward.
Swaddles vs. Sleep Sacks
For the first weeks of life, many parents use a swaddle, which wraps snugly around the baby’s arms and torso. Newborns often sleep better swaddled because it reduces their startle reflex. You need to stop swaddling as soon as your baby shows any signs of trying to roll over, which can happen as early as 2 months.
Once you stop swaddling, switch to a sleep sack (also called a wearable blanket). Sleep sacks are designed to stay on without covering your baby’s face, and they let your baby move freely. The AAP says sleep sacks that don’t compress the arms can be used for as long as you want. They replace loose blankets, which should never be in the crib. Loose blankets, pillows, bumper pads, and soft toys all increase the risk of suffocation.
Choosing the Right Fabric
Cotton is the most common choice for newborn sleepwear, and for good reason. It’s breathable, widely available, and affordable. The downside is that cotton absorbs moisture but doesn’t release it quickly, so if your baby sweats, the fabric can stay damp against their skin.
Bamboo viscose is a popular alternative. It pulls moisture away from the skin more effectively than cotton and naturally adjusts to temperature changes, keeping your baby warmer in cool rooms and cooler in warm ones. If your baby tends to run hot or sweats during sleep, bamboo is worth trying. Both fabrics are safe and breathable. Avoid heavy synthetic materials for sleepwear since they trap heat more easily.
How to Check for Overheating
The best way to gauge your baby’s temperature is to touch the back of their neck or their chest. These areas give you a more accurate read than hands or feet, which tend to feel cool on newborns regardless of their core temperature. Your baby’s chest should feel warm but not hot or sweaty.
Signs your baby is too warm include:
- Flushed or red skin
- Sweating or damp hair (though babies can overheat without visible sweat)
- Fussiness or restlessness
- A hot chest
- Heat rash: tiny red bumps in skin folds, around the neck, or on the bottom
If you notice any of these, remove a layer or switch to lighter clothing. Overheating is a known risk factor for sleep-related infant deaths, so when in doubt, dress lighter rather than heavier. A slightly cool room is safer than a warm one.
Skip the Hat Indoors
Newborns lose heat through their heads, which is helpful for temperature regulation. The CDC specifically advises not covering your baby’s head during sleep. Hats are great for going outside in cold weather, but remove them once you’re back indoors and always before putting your baby down to sleep.
Sleepwear That Makes Nighttime Easier
You’ll be changing diapers multiple times a night, so how the clothing opens matters almost as much as what it’s made of. Sleeper gowns with open or knotted bottoms give you instant diaper access. You lift the gown, change the diaper, and pull it back down without unzipping or unsnapping anything. These work especially well for the first three months.
Two-way zippers are another practical option. They unzip from the bottom so you can access the diaper while keeping your baby’s chest covered and warm. Magnetic closures snap together on their own and work in complete darkness with one hand, which sounds like a luxury until you’re doing your fourth diaper change at 3 a.m. and it becomes essential. These tend to cost more but remain usable through the first nine months or so.
Putting It All Together
A simple nightly routine: check your room temperature, pick a base layer (onesie or footed pajama), and add a swaddle or sleep sack with the appropriate TOG rating. Touch your baby’s chest after about 10 minutes to confirm they feel warm but not hot. Adjust from there. Most parents find their go-to combination within the first week or two and only need to change it when the seasons shift or the thermostat changes.
The one-extra-layer rule from the NHS is the easiest guideline to remember. If you’re comfortable in a t-shirt, your baby likely needs a onesie plus a light sleep sack. If you’re reaching for a sweater, your baby probably needs footed pajamas with a warmer sleep sack. Trust the room temperature, check their chest, and keep the crib clear of everything except a fitted sheet and your baby.