Babies sleep safest and most comfortably in fitted clothing like a onesie or footed sleeper, with no loose blankets, hats, or extra bedding. The general rule is to dress your baby in no more than one layer beyond what you’d wear comfortably in the same room. That simple guideline, combined with the right room temperature and a few key safety rules, covers most situations.
The One-Layer Rule
The American Academy of Pediatrics recommends dressing infants in layers of clothing rather than using blankets, which pose suffocation and entrapment risks. Loose bedding, including blankets, quilts, and comforters, is the most common cause of accidental infant suffocation during sleep. The safest approach is to skip blankets entirely and rely on what your baby is actually wearing.
A practical way to think about it: if you’re comfortable in a t-shirt in your baby’s room, your baby can wear a short-sleeve onesie plus one additional layer, like a sleep sack. If you’d want a light sweater, your baby might need a long-sleeve sleeper or a slightly warmer wearable blanket. You don’t need to overthink it. Babies who are dressed appropriately for the room temperature sleep better and more safely than babies bundled in extra layers.
What to Wear at Common Room Temperatures
The ideal nursery temperature falls between 68°F and 72°F. At that range, most babies do well in a long-sleeve onesie or footed pajamas paired with a lightweight sleep sack. Here’s how to adjust from there:
- Above 75°F: A short-sleeve bodysuit alone, or even just a diaper. If using a sleep sack, choose one rated at 0.2 TOG (the thinnest available).
- 68°F to 75°F: A onesie or footed sleeper with a 1.0 TOG sleep sack. This is the sweet spot for most homes.
- 61°F to 68°F: A long-sleeve bodysuit or footed pajamas with a 2.5 TOG sleep sack. Add a layer underneath rather than piling blankets on top.
TOG is a rating that measures how much warmth a fabric traps. The higher the number, the warmer the garment. Most sleep sack packaging lists the TOG rating and a suggested temperature range, which makes matching straightforward.
Why Sleep Sacks Replace Blankets
A wearable blanket, or sleep sack, is the AAP’s recommended alternative to traditional blankets. It keeps your baby warm without the risk of fabric riding up over the face or bunching around the nose and mouth. Sleep sacks zip on and stay in place, so there’s nothing loose in the crib.
You can start using a sleep sack from birth. They come in different TOG ratings and sizes, so you’ll swap them out as your baby grows and as seasons change. The key is that the neck opening fits snugly enough that your baby’s head can’t slip inside.
Swaddling: When to Start and Stop
Swaddling is safe for newborns who aren’t yet showing any signs of rolling. A snug swaddle can reduce the startle reflex and help very young babies settle. But the window is short. You need to stop swaddling as soon as your baby starts trying to roll over, which typically happens between 2 and 6 months.
Signs it’s time to transition out of a swaddle include: rolling during playtime, pushing up on hands during tummy time, lifting legs and flopping them to the side, or regularly breaking free from the swaddle. Once any of these appear, switch to a sleep sack that leaves the arms free. A swaddled baby who rolls onto their stomach can’t use their arms to push up or reposition, which creates a serious suffocation risk.
No Hats Indoors
Babies lose heat through their heads, which is actually a feature, not a problem. That head-cooling mechanism is one of the main ways infants regulate their body temperature. Putting a hat on a sleeping baby blocks that process and raises the risk of overheating. Research in neonatal intensive care units found that hats were unnecessary for maintaining a stable temperature once babies were in open cribs, and the AAP advises against hats indoors except during the first few hours after birth.
A hat can also slip down over a baby’s face during sleep. There’s no benefit that outweighs these risks in a normal home environment.
Choosing the Right Fabric
Cotton and bamboo viscose are the two most common fabrics for baby sleepwear, and both work well. Cotton is breathable and widely available. Bamboo viscose is about 40 percent more absorbent than organic cotton and wicks moisture faster, which can help babies who tend to sleep hot or sweat during the night. Its fiber structure allows slightly better airflow than cotton.
Whichever fabric you choose, avoid fleece or heavy knits in warm rooms. The goal is a material that lets heat escape gradually rather than trapping it against your baby’s skin. Synthetic materials that don’t breathe well can contribute to overheating even when the room temperature seems fine.
How to Tell if Your Baby Is Too Warm
The best way to check is to feel your baby’s chest or the back of the neck. Hands and feet run cool in babies and aren’t reliable indicators. If your baby’s torso feels hot or clammy, they’re likely overdressed.
Other signs of overheating include flushed or red skin, damp hair, unusual fussiness or restlessness, and sluggish or listless behavior. Babies can overheat without visibly sweating, so skin temperature is a more reliable check than looking for sweat. If your baby feels warm, remove a layer or switch to a lower-TOG sleep sack rather than adjusting the thermostat alone.
Overheating is a known risk factor for sleep-related infant deaths, which is why erring slightly on the cooler side is safer than overdressing. A baby who is a little cool will wake up and fuss. A baby who is too warm faces a more serious risk.
What to Avoid in the Crib
The crib should contain a firm mattress with a fitted sheet and your dressed baby. Nothing else. That means no loose blankets, pillows, stuffed animals, bumper pads, quilts, comforters, or mattress toppers. It also means no weighted sleep sacks or weighted swaddles, which are not recommended by the AAP.
If your baby’s sleepwear has strings, ties, or decorative elements that could come loose, save it for daytime. Sleep clothing should be simple, well-fitted, and free of anything that could wrap around fingers, toes, or the neck.