Newborns sleep safest in a single layer of fitted clothing, like a onesie or footed pajama, with a swaddle or wearable sleep sack instead of a loose blanket. The exact combination depends on your room temperature, but the goal is always the same: keep your baby warm enough without any risk of overheating or loose fabric covering their face.
The Basic Setup
A good starting point is one fitted layer plus a sleep sack or swaddle. In a room kept between 68 and 72 degrees Fahrenheit (the recommended range for a baby’s sleep space), that typically means a short-sleeve or long-sleeve bodysuit underneath a lightweight wearable blanket. If you’re using footed pajamas, which cover the arms, legs, and feet in one piece, you may not need an additional layer at all in a warm room.
The simplest rule: dress your baby in one more layer than you’d be comfortable wearing yourself. If you’d sleep fine in a t-shirt, your newborn likely needs a bodysuit plus a light sleep sack. If you’d want a long-sleeve shirt, a footed sleepsuit with or without a thin sleep sack is a reasonable choice.
Keep all blankets, pillows, stuffed animals, and bumpers out of the crib. A wearable sleep sack is the safe alternative to a blanket because it stays in place and can’t ride up over your baby’s face.
Sleepwear Types and When to Use Each
Bodysuits (onesies): These cover the torso and snap at the crotch, leaving the legs bare. They work well as a base layer under a sleep sack, or on their own in very warm rooms. Short-sleeve versions are best for summer; long-sleeve for cooler months.
Footed sleepsuits: These are full-length one-piece outfits that cover arms, legs, and feet. They’re designed specifically for nighttime and provide whole-body warmth without extra blankets. Many have snap or zipper closures for easy diaper changes, and some include built-in hand mittens to prevent scratching. In a room at 68 to 72 degrees, a footed sleepsuit on its own is often enough.
Wearable sleep sacks: These are essentially sleeping bags your baby wears. They zip over whatever base layer you’ve chosen and replace loose blankets entirely. Sleep sacks come in different thicknesses rated by a system called TOG, which measures thermal resistance. A higher TOG number means a warmer sack.
Matching Layers to Room Temperature
TOG ratings take the guesswork out of layering. Here’s how they line up with room temperature:
- 75°F to 81°F: Use a 0.2 TOG sleep sack (very thin, almost like a sheet) over just a diaper or a short-sleeve bodysuit.
- 68°F to 75°F: A 1.0 TOG sack over a short-sleeve bodysuit works well. This covers the most commonly recommended nursery range.
- 64°F to 72°F: A 1.5 TOG sack, possibly with a long-sleeve bodysuit underneath.
- 61°F to 68°F: A 2.5 TOG sack over a long-sleeve bodysuit or light sleepsuit.
- Below 61°F: A 3.5 TOG sack over a sleepsuit. This is for genuinely cold rooms.
If your home runs warm in summer and you don’t have air conditioning, a diaper paired with a thin cotton sleep sack may be all your baby needs. Overdressing in warm weather is a more common mistake than underdressing.
Why Cotton Is the Best Fabric Choice
Cotton is the go-to fabric for newborn sleepwear. It absorbs moisture from sweat, allows airflow against the skin, and releases heat efficiently, all of which help your baby maintain a stable temperature overnight. Its porous structure creates a comfortable microclimate inside the clothing layer.
Polyester and synthetic blends work differently. Polyester is hydrophobic, meaning it repels moisture rather than absorbing it, which can trap perspiration against your baby’s skin. It also retains heat within the fabric, especially in fleece or brushed knits. That heat retention might sound appealing in winter, but in sleepwear it increases the risk of overheating, particularly in warm rooms or humid climates. Cotton is also naturally hypoallergenic, making it less likely to cause skin irritation. When shopping for sleep sacks and pajamas, look for 100% cotton or cotton-rich blends.
No Hats Indoors
Newborns often come home from the hospital wearing a little knit cap, but hats should not be worn for sleep once you’re home. The AAP specifically recommends against hats indoors except during the first hours after birth or in the NICU. Babies regulate a significant amount of body heat through their heads, so covering it during sleep can contribute to dangerous overheating. A hat can also slip down over a baby’s face during the night.
Swaddling: When It Works and When to Stop
Swaddling is a safe option for newborns who haven’t started rolling. A snug swaddle mimics the feeling of the womb and can help calm the startle reflex that wakes many newborns. You can swaddle with a thin cotton blanket wrapped securely, or use a purpose-built swaddle wrap with velcro or snaps.
Under the swaddle, your baby needs only a light layer, typically a short-sleeve bodysuit in a comfortable room. Adding too much underneath a swaddle is a common cause of overheating.
The critical safety rule: stop swaddling as soon as your baby shows any signs of rolling over. Once a baby can roll onto their stomach, a swaddle restricts the arm movement they need to push themselves up or reposition, which creates a suffocation risk. This milestone can happen as early as two months for some babies. At that point, transition to a sleep sack that leaves the arms free.
How to Check if Your Baby Is Too Warm
The most reliable way to check is to touch the back of your baby’s neck or their chest. These areas reflect core body temperature better than hands or feet, which tend to feel cool in newborns regardless of how warm they are. The skin should feel warm but not hot or sweaty.
Signs your baby may be overheating include flushed or red skin, sweating or damp hair, unusual fussiness or restlessness, and sluggish or listless behavior. Some babies overheat without visible sweating, so skin temperature is a better indicator than waiting to see sweat. If your baby feels hot, remove a layer or switch to a lower-TOG sleep sack and check again in 10 to 15 minutes.
Overheating is a known risk factor for SIDS, which is why getting the layers right matters more than it might seem. When in doubt, slightly cooler is safer than slightly warmer. A baby who is a bit cool will wake and fuss; a baby who is overheating may not.
Putting It All Together
For a room kept at the recommended 68 to 72 degrees, a practical setup looks like this: a cotton short-sleeve bodysuit, a 1.0 TOG cotton sleep sack, and nothing else. No hat, no socks (the sleep sack covers the feet), no loose blankets. For warmer rooms, strip down to a diaper and a thin sack. For cooler rooms, add a long-sleeve base layer and increase the TOG rating.
Check your baby’s neck or chest before you go to bed yourself. Adjust layers as seasons change or if your thermostat isn’t consistent overnight. The right combination keeps your baby sleeping comfortably and safely without any loose items in the crib.