Newborns sleep in a crib or bassinet with a firm, flat mattress and a fitted sheet, and nothing else in the sleep space. For clothing, they wear a onesie or pajamas under a swaddle or sleep sack, with no loose blankets. That’s the full picture, but the details matter because many popular baby products are actually unsafe for sleep.
The Sleep Surface: Crib or Bassinet
The only safe sleep surfaces for a newborn are a safety-approved crib, bassinet, or portable play yard with a firm, flat mattress covered by a single fitted sheet. “Firm” means the mattress doesn’t indent when your baby lies on it. “Flat” means no angle or incline whatsoever.
Place the crib or bassinet in your bedroom for at least the first six months. Room sharing (not bed sharing) lets you hear and respond to your baby while keeping them on their own safe surface. The risk of sleep-related infant death is 5 to 10 times higher when babies under four months share a bed with an adult, and up to 67 times higher when an infant sleeps with someone on a couch, soft armchair, or cushion.
What Should Not Be in the Crib
The crib should contain your baby and a fitted sheet. That’s it. No blankets, pillows, stuffed animals, or positioning devices. Crib bumpers, including padded bumpers, vinyl bumper guards, and vertical slat covers, are federally banned in the United States as of November 2022 under the Safe Sleep for Babies Act. Non-padded mesh liners are the only exception.
Inclined sleepers like the Fisher-Price Rock ‘n Play are also banned. Babies have poor head control and can slouch forward on an incline, tucking their chin to their chest and compressing their airway. The majority of deaths linked to inclined sleepers happened when babies shifted position during sleep. For the same reason, swings, bouncers, strollers, and car seats should never be used for routine sleep, even if your baby falls asleep in one.
What a Newborn Wears to Sleep
Since loose blankets are off the table, your baby’s clothing is their warmth. The standard setup is a base layer (a bodysuit or footed pajamas) plus a swaddle or wearable sleep sack over it. The right combination depends on how warm the room is.
Sleep sacks are rated using a TOG (Thermal Overall Grade) number. Lower TOG means thinner and cooler, higher means warmer:
- 0.2 TOG: for rooms between 75°F and 81°F (a light muslin layer)
- 1.0 TOG: for rooms between 68°F and 75°F
- 2.5 TOG: for rooms between 61°F and 68°F
- 3.5 TOG: for rooms below 61°F
In a room kept around 70°F, a 1.0 TOG sleep sack over a long-sleeved onesie works well for most babies. Don’t layer two sleep sacks or swaddles on top of each other, as this raises the risk of overheating or suffocation. Instead, choose the right TOG and adjust the clothing underneath. If your baby is sweating, feels hot to the touch, or has flushed skin, they’re overdressed. Cold hands and feet or fussiness can signal they need another layer.
Ideal Room Temperature
Keep the room between 68°F and 78°F. A fan on low helps circulate air and has been associated with reduced SIDS risk. Overheating is a known risk factor for sleep-related infant death, so it’s better to err slightly cool and add a clothing layer than to make the room too warm.
Swaddles vs. Sleep Sacks
Swaddles wrap your newborn snugly with their arms contained, which helps dampen the startle reflex that wakes them. They’re appropriate only for the earliest weeks. As soon as your baby shows any sign of rolling over, you need to stop swaddling immediately. Most babies begin showing these signs between 2 and 6 months old.
Signs it’s time to transition out of a swaddle include: rolling or attempting to roll during playtime, pushing up on hands during tummy time, lifting their legs and flopping them to the side, breaking free of the swaddle, or resisting being wrapped. Once you see any of these, switch to a sleep sack that leaves the arms free. Sleep sacks are safe to use well into toddlerhood and serve as a blanket replacement for as long as your child fits in one.
Products to Avoid
Weighted sleep sacks, weighted swaddles, and weighted blankets are not safe for infants. The CPSC, CDC, NIH, and AAP all warn against them. A newborn’s rib cage is flexible, not rigid, so even modest pressure can make it harder for them to breathe and for their heart to beat properly. There is also evidence that weighted products can lower oxygen levels, which may harm a developing infant’s brain. The AAP has compared the situation to inclined sleepers, which remained on the market until they were linked to over 100 infant deaths.
Dock-a-tot style loungers, positioners, and nests are also not designed for unsupervised sleep, even though they’re frequently marketed alongside sleep products. If a product isn’t specifically sold as a crib, bassinet, or play yard that meets federal safety standards, it shouldn’t be your baby’s sleep surface.