Place your baby on their back for every sleep, including naps and nighttime, from birth through their first birthday. This single positioning rule is the most important thing you can do to reduce the risk of sudden infant death syndrome (SIDS). After the “Back to Sleep” campaign launched in 1992, SIDS rates in California alone dropped 47 percent within six years. The guideline hasn’t changed since: back sleeping on a flat, firm surface is the standard.
Why Back Sleeping Is Safer
The reason comes down to basic anatomy. When a baby sleeps on their back, the windpipe sits on top of the esophagus (the tube to the stomach). If milk or stomach fluid comes back up, it has to travel against gravity to reach the airway, which makes choking unlikely. Flip that arrangement over and the physics reverse: with a baby on their stomach, the esophagus sits above the windpipe. Fluids pool right at the airway opening, making choking far more likely.
This is the opposite of what many parents expect. A common worry is that a back-sleeping baby will choke on spit-up, but the anatomy actually protects against that. Stomach-sleeping babies are at greater risk of choking, not less.
What About Babies With Reflux?
If your baby spits up frequently or has been diagnosed with gastroesophageal reflux, you may feel tempted to prop them at an angle or place them on their side. Research doesn’t support either approach. Studies using pH probes and other monitoring tools have found that inclined positions don’t reduce reflux. One study found that the left side-lying position reduced the number of reflux episodes measured by instruments, but that reduction didn’t translate into fewer symptoms like crying or irritability.
The American Academy of Pediatrics is clear: even babies with reflux should sleep flat on their backs. Placing an infant on an inclined surface can actually cause them to slide into a position that compresses their airway.
Inclined Sleepers Are Banned
Products marketed as “inclined sleepers,” including some that were enormously popular for years, are now illegal to sell in the United States. The Safe Sleep for Babies Act of 2021 banned any sleep product with a surface angled more than ten degrees for infants up to one year old. The ban took effect in November 2022 and applies regardless of when the product was manufactured. If you still have one of these products at home, it should not be used for sleep.
This includes padded loungers and rockers often marketed as soothing tools. If a product has a reclined or cradled shape, it is not a safe sleep surface. Your baby can nap in your arms in a rocker while you’re awake and watching, but unattended sleep should only happen on a flat, firm mattress in a crib or bassinet.
The Right Sleep Surface
A firm, flat mattress is essential. Federal safety standards now include a specific firmness test for crib mattresses to prevent suffocation on surfaces that are too soft. Memory foam, pillow-top mattresses, and adult mattresses do not meet these standards. A properly sized crib mattress should fit snugly in the crib frame with no gaps larger than about three inches at the corners, even after the fitted sheet has been washed and shrunk.
The mattress should have nothing on it except a fitted sheet. No blankets, pillows, stuffed animals, bumper pads, or positioning wedges. These items can press against a baby’s face and block breathing. If you’re worried about your baby being cold, dress them in a wearable blanket or sleep sack instead of using a loose blanket.
When Your Baby Starts Rolling
At some point, usually between two and four months, your baby will start trying to roll over. This is when two things change. First, if your baby rolls onto their stomach during sleep on their own, and they can roll both directions (back to tummy and tummy to back), you can leave them in whatever position they settle into. You don’t need to flip them back over all night. You should still always place them on their back at the start of every sleep.
Second, rolling is the signal to stop swaddling. A swaddled baby who rolls onto their stomach cannot use their arms to push up or reposition, which creates a suffocation risk. Some babies begin working on rolling as early as two months, so watch for the signs: arching, rocking side to side, or pushing up during tummy time. The moment you see attempts at rolling, transition out of any swaddle that restricts the arms. Sleep sacks that leave the arms free remain safe.
Room Sharing Without Bed Sharing
The CDC recommends keeping your baby’s crib or bassinet in your bedroom for at least the first six months. Room sharing makes nighttime feeding easier and lets you monitor your baby, and it’s associated with lower SIDS risk. Bed sharing is different and carries real dangers. Adult beds have soft mattresses, pillows, and blankets that can obstruct a baby’s airway. There’s also the risk of an adult rolling onto the baby during sleep.
The safest setup is a crib or bassinet right next to your bed. Bedside bassinets with one lowered wall can give you the closeness of co-sleeping with a separate, firm sleep surface for the baby.
Room Temperature and Overheating
Overheating is an independent risk factor for SIDS. A room temperature between 68 and 72 degrees Fahrenheit (20 to 22 degrees Celsius) is generally comfortable for a sleeping baby. Anything above 72°F may be too warm. A good rule of thumb: dress your baby in one layer more than you’d find comfortable, then check their chest. If their chest feels warm or damp to the touch, remove a layer or lower the thermostat. Sweating, flushed skin, or damp hair are signs your baby is too hot.
Hats should not be worn indoors during sleep. Babies release excess heat through their heads, and covering it interferes with temperature regulation. Fans circulating air in the room can also help maintain a safe temperature.