Babies sleep safest in fitted sleepwear on a firm, flat mattress with nothing else in the crib. No blankets, no pillows, no stuffed animals. The ideal setup is simple: a safety-approved crib with a fitted sheet, and your baby dressed in one layer more than you’d wear comfortably in the same room.
The Only Things That Belong in the Crib
A firm, flat mattress covered by a fitted sheet is the entire sleep surface your baby needs. That means no loose blankets, pillows, bumper pads, or soft toys. These items create suffocation risks, even when they seem harmless. The goal is a completely bare crib with nothing but the sheet and your dressed baby.
The “one layer more than an adult” rule is the simplest way to gauge how to dress your baby. If you’re comfortable in a t-shirt, your baby is fine in a onesie plus a sleep sack. If you’d want a light sweater, add a slightly warmer layer. This principle works across seasons and keeps you from overdressing, which is actually the more common mistake.
Sleep Sacks Replace Blankets
Since loose blankets aren’t safe, a wearable blanket (sleep sack) is the standard way to keep your baby warm. Sleep sacks zip on over your baby’s clothes and leave their arms free while enclosing their legs and torso in a pouch of fabric. They can’t ride up over your baby’s face the way a blanket can.
Sleep sacks come with a TOG rating, which tells you how warm they are. Match the TOG to your nursery temperature:
- 0.2 TOG: 75°F to 81°F (very warm rooms, summer)
- 1.0 TOG: 68°F to 75°F (most climate-controlled homes)
- 1.5 TOG: 64°F to 72°F (slightly cool rooms)
- 2.5 TOG: 61°F to 68°F (cold rooms, winter)
- 3.5 TOG: below 61°F (very cold environments)
For most homes kept between 68 and 72 degrees Fahrenheit (the recommended nursery range), a 1.0 TOG sleep sack over a cotton onesie or footed sleeper does the job year-round.
Swaddles for Newborns, but Not for Long
Swaddling helps calm the startle reflex that wakes newborns, and many parents find it essential in the first weeks. A proper swaddle wraps snugly around the arms and chest while leaving the hips loose enough to bend naturally. You can use a swaddle blanket or a zip-up swaddle product designed for the purpose.
The critical rule: stop swaddling the moment your baby shows any signs of trying to roll over. A swaddled baby who rolls onto their stomach may not be able to roll back, and that’s a suffocation risk. Many babies start attempting to roll around 2 months, though the typical window is 3 to 6 months. Once you see those early signs of rolling, or your baby is breaking free of the swaddle regularly, it’s time to switch to a sleep sack with arms out. The startle reflex usually fades by 4 to 5 months anyway, so most babies are ready for the transition by then.
Comparing Sleepwear Styles
You’ll find three main types of baby sleepwear, and each has trade-offs for those middle-of-the-night diaper changes.
Footed sleepers with zippers are the most popular choice. A two-way zipper that opens from the bottom lets you change a diaper without exposing your baby’s chest to cold air. Sleepers that only zip downward from the neck are better for blowout situations, since you can pull the whole thing off easily. One downside: a footed sleeper that’s slightly too big tends to bunch up awkwardly around the middle.
Knotted gowns are a favorite for the newborn weeks. You just lift the bottom of the gown to check or change a diaper without any zippers or snaps. No wrangling tiny legs back into anything in dim light. The downsides are that gowns tend to ride up on active babies, and they don’t work well with swaddles, car seats, or baby carriers.
Bodysuits with snaps (including kimono-style wraps) give you flexibility. You can unsnap just one or two at the diaper line to check if baby is wet, or pair a bodysuit with separate pants you can remove if the room gets warm. Kimono-style tops that wrap and snap at the side mean you never have to pull anything over a newborn’s head, which many parents appreciate in the early days.
Choosing the Right Fabric
Cotton is the classic choice for baby sleepwear: breathable, soft, and easy to wash. For babies who run hot or sweat during sleep, bamboo viscose is worth considering. It’s about 40 percent more absorbent than organic cotton and wicks moisture away faster, keeping skin drier overnight. The fiber structure allows more airflow than cotton, which helps with temperature regulation. Either fabric works well. Avoid polyester and fleece for warmer rooms, as they trap heat.
What Not to Use
A few products marketed for infant sleep are actually unsafe:
Weighted sleep sacks and swaddles have been flagged by the CPSC, AAP, CDC, and NIH as dangerous. The weight presses on a newborn’s still-flexible rib cage, making it harder to breathe and potentially affecting heart function. There’s also evidence that weighted products can lower oxygen levels in ways that may harm a developing brain. These agencies have compared the risk to inclined sleepers like the Rock ‘N Play, which were linked to over 100 infant deaths before being recalled.
Hats and beanies indoors should come off once you leave the hospital. Babies lose excess heat through their heads, and covering that escape route raises the risk of overheating. Overheating during sleep is an independent risk factor for SIDS.
Loose socks and mittens can come off and become a choking or suffocation hazard. If your baby’s hands or feet are cold, a footed sleeper or a sleep sack that covers the feet is a safer solution.
How to Tell if Your Baby Is Too Warm
Cold hands and feet are normal in babies and don’t mean they need more layers. The reliable spot to check is the back of the neck or the chest. If the skin there feels hot, sweaty, or damp, your baby is overdressed.
Other signs of overheating include flushed or red skin, damp hair, unusual fussiness or restlessness, and seeming unusually sluggish or limp. Heat rash, which looks like tiny red bumps in skin folds and around the neck, is another signal that your baby has been too warm. If you’re unsure, it’s always safer to remove a layer. Babies tolerate being slightly cool much better than being too hot.
Putting It All Together by Age
Newborn to 2 Months
A diaper, a onesie or knotted gown, and a swaddle. In warmer rooms, skip the onesie and swaddle over just a diaper. Keep the room between 68 and 72°F and skip the hat indoors.
2 to 4 Months
Watch closely for rolling. At the first sign, transition out of the swaddle into a sleep sack. A bodysuit or footed sleeper under the sleep sack is usually enough. Match the sleep sack’s TOG rating to your room temperature.
4 Months and Beyond
A sleep sack over a single layer of clothing is the standard setup until your child transitions to a toddler bed, typically around 18 to 24 months. By this point, most babies have outgrown the startle reflex entirely, and the sleep sack simply replaces the blanket they still can’t safely use.