Safe sleep is a set of evidence-based practices designed to protect infants from suffocation, strangulation, and sudden infant death syndrome (SIDS) while they sleep. In the United States, approximately 3,700 babies die each year from sudden unexpected causes during sleep, including 1,529 from SIDS, 1,040 from accidental suffocation and strangulation in bed, and 1,131 from unknown causes. Most of these deaths are preventable by following a few straightforward guidelines.
The ABCs: Alone, Back, Crib
The simplest way to remember safe sleep is the ABCs: Alone, on their Back, in a Crib. These three rules form the foundation of every major pediatric sleep safety recommendation.
Alone means your baby sleeps in their own space with no other people, no stuffed animals, no pillows, and no loose blankets. Back means placing your baby on their back for every sleep, including naps. Crib means using a crib, bassinet, or portable play yard with a firm, flat mattress and a fitted sheet, nothing else.
Why Back Sleeping Matters
The reason back sleeping is so strongly recommended comes down to basic anatomy. When a baby sleeps on their back, the windpipe sits above the esophagus (the tube to the stomach). If milk or fluid comes up from the stomach, it has to work against gravity to reach the airway. That makes choking far less likely, not more, which surprises many parents who assume the opposite.
When a baby sleeps on their stomach, that arrangement flips. The esophagus sits above the windpipe, so any fluid that comes up pools right at the airway opening. Beyond the choking risk, stomach sleeping increases the chance of overheating and of rebreathing already-exhaled air. That trapped air contains too much carbon dioxide and too little oxygen, which can affect heart and lung function and reduce oxygen reaching the brain. Healthy babies naturally swallow or cough up fluids as a reflex, so the fear that a back-sleeping baby will choke on spit-up is largely unfounded.
What Goes in the Crib
The answer is almost nothing. A firm, flat mattress with a single fitted sheet is all your baby needs. Every additional object, whether it’s a blanket, pillow, stuffed animal, or bumper pad, introduces a suffocation risk. In a study of 190 infant suffocation deaths attributed to soft bedding, the causes included adult mattresses, blankets, pillows, and couch cushions obstructing the baby’s airway.
Crib bumper pads, which many parents assume are protective, accounted for deaths in that same dataset. They offer no meaningful safety benefit and can press against a baby’s face, blocking airflow. Weighted blankets, sleep positioners, and wedges are also unsafe for infants. If you’re worried about your baby being cold, a wearable blanket or sleep sack is the safest alternative to loose bedding.
Any product with an incline greater than 10 degrees, such as rockers, gliders, swings, and infant bouncers, should never be used for sleep. These products can cause a baby’s head to fall forward, compressing the airway.
Room Sharing vs. Bed Sharing
Room sharing and bed sharing sound similar but carry very different levels of risk. The American Academy of Pediatrics recommends placing your baby’s crib, bassinet, or play yard in your bedroom for at least the first six months. Having your baby nearby makes nighttime feeding easier and lets you monitor them closely.
Bed sharing, where the baby sleeps on the same surface as an adult, is a different story. A meta-analysis of 11 studies found that bed sharing nearly triples the risk of SIDS compared to sleeping on a separate surface. Certain situations make the risk dramatically higher:
- More than 10 times the baseline risk: Sharing a bed with someone impaired by alcohol, sedating medications, or extreme fatigue. Sharing a bed with a smoker, even if they never smoke in bed. Sleeping with a baby on a soft surface like a couch, waterbed, or armchair.
- 5 to 10 times the baseline risk: Bed sharing with a healthy, full-term baby younger than 4 months, regardless of other factors. Sharing a bed with anyone who is not the baby’s parent, including siblings or other caregivers.
- 2 to 5 times the baseline risk: Bed sharing with a premature or low birth weight baby. Sleeping with soft bedding accessories like pillows or blankets on the bed.
Falling asleep with a baby on a couch or armchair is especially dangerous, carrying a 22- to 67-fold increased risk of death from suffocation, entrapment between cushions, or overlay. If you’re feeding your baby at night and feel yourself getting drowsy, it’s safer to move to a bed (without loose bedding) than to risk falling asleep on a sofa.
Temperature and Overheating
Overheating is an independent risk factor for SIDS, so keeping the sleep environment at a comfortable temperature matters. Aim for a room temperature between 68 and 72°F (20 to 22°C), and avoid going above 75°F (23.8°C). Dress your baby in one layer more than you’d wear comfortably in the same room.
Signs that a baby is overheating include flushed or red skin, sweating or damp hair (though some babies overheat without sweating), fussiness, a rapid heart rate, and unusual sluggishness. The back of the neck or chest is a more reliable spot to check than the hands or feet, which tend to feel cooler naturally.
Swaddling Safely
Swaddling can help calm a newborn, and it’s considered safe when done correctly. The key rules: always place a swaddled baby on their back, use a firm and flat sleep surface, and make sure the swaddle isn’t too tight around the hips (which can affect joint development).
The hard deadline for swaddling is the moment your baby shows signs of rolling over. Once a baby can roll, being swaddled prevents them from using their arms to push up and reposition, which turns the swaddle from a comfort tool into a suffocation hazard. Most babies begin rolling between 2 and 4 months, so watch for early signs and transition to a sleep sack before that milestone hits.
Pacifiers and Other Protective Factors
Offering a pacifier at sleep time is one of the simpler things you can do to reduce risk. A large meta-analysis found that pacifier use during sleep cut the odds of SIDS by roughly half. Researchers aren’t entirely sure why, but the leading theories involve pacifiers keeping the airway slightly more open and promoting lighter sleep that makes it easier for a baby to rouse if something goes wrong. If you’re breastfeeding, wait until nursing is well established (usually around 3 to 4 weeks) before introducing one. If the pacifier falls out after your baby falls asleep, you don’t need to put it back in.
When Your Baby Starts Rolling
Once your baby can roll from back to front and front to back on their own, you can stop repositioning them if they roll onto their stomach during sleep. The ability to roll independently means they have enough head and neck control to manage their airway. Continue placing them on their back at the start of every sleep, but let them find their own position after that. This is also the point where you must stop using a swaddle and switch to a wearable blanket that leaves the arms free.