Infants should always be placed on their backs to sleep, on a firm, flat mattress, in their own sleep space with nothing else in it. This single practice is the most important thing parents can do to reduce the risk of Sudden Infant Death Syndrome (SIDS), which caused 1,529 deaths in the United States in 2022. The guidelines are straightforward, but the details matter.
Why Back Sleeping Is Safest
When a baby lies on their back, the windpipe sits above the food tube (esophagus). If the baby spits up, gravity pulls the liquid down to the lowest point, away from the airway. Flip a baby onto their stomach, and that arrangement reverses: spit-up can pool near the airway opening instead of draining away from it. This is the opposite of what many parents intuitively fear. Back sleeping protects against choking, not the other way around.
Place your baby on their back for every sleep, including naps. This applies from birth until the baby can roll both ways on their own, which typically happens around six months. At that point, a baby’s brain is mature enough to alert them to breathing problems, so if they roll onto their stomach during the night, you don’t need to flip them back. You should still start every sleep on the back, though, and let your baby choose their position from there.
The Right Sleep Surface
Your baby needs a crib, bassinet, or portable play yard with a firm, flat mattress and a fitted sheet. That’s it. Nothing else goes in the sleep space: no loose blankets, pillows, stuffed animals, crib bumpers, or soft padding of any kind. Soft bedding is one of the leading contributors to sleep-related infant deaths because it can conform around a baby’s face and block airflow.
Crib mattresses sold in the United States must pass a federal firmness test under safety standards enforced by the Consumer Product Safety Commission. If you’re buying new, look for a mattress that meets the current ASTM standard (F2933). If you’re using a hand-me-down, check that the mattress is still firm and hasn’t softened or developed indentations over time. A good rule of thumb: press on the center and edges. If the mattress holds its shape and springs back quickly, it’s still suitable.
Inclined sleepers, products with a sleep surface angled more than 10 degrees, are banned in the United States as of November 2022 under the Safe Sleep for Babies Act. These products were linked to dozens of infant deaths before the ban. If you have one from before the ban or receive one secondhand, do not use it for sleep.
Where the Crib Should Go
The AAP recommends that your baby sleep in your bedroom, in their own crib or bassinet, for at least the first six months and ideally up to 12 months. Room sharing, not bed sharing, is the key distinction here. Having your baby nearby makes nighttime feeding easier and lets you monitor them, but sharing an adult bed introduces real hazards.
Babies who room-share with parents are four times more likely to end up in the adult bed during the night, and when they do, they’re more likely to be surrounded by pillows, blankets, and other unsafe items. Adult mattresses are too soft for infants, and the risk of a parent rolling onto or against the baby is significant, especially when the parent is sleep-deprived. Couches and armchairs are even more dangerous. Falling asleep while holding your baby on a sofa is one of the highest-risk scenarios for suffocation.
What Your Baby Should Wear
Since loose blankets don’t belong in the crib, dress your baby in a wearable blanket or sleep sack to keep them warm. Choose a layer appropriate for the room temperature. A good guideline: if the room feels comfortable to you in light clothing, one layer plus a sleep sack is usually enough. Check the back of your baby’s neck or their chest to gauge temperature. Warm, slightly damp skin there means they’re too hot. Cool hands and feet are normal and not a reliable sign of being cold.
Overheating is a known risk factor for SIDS, so err on the side of slightly cooler rather than warmer. Skip hats indoors, as babies regulate heat through their heads.
Swaddling Safety
Swaddling can help calm newborns and improve sleep in the first weeks of life, but it comes with a firm expiration date. You must stop swaddling as soon as your baby shows any signs of rolling over. For some babies, this happens as early as two months. A swaddled baby who rolls onto their stomach cannot use their arms to push up or reposition, which creates a suffocation risk.
Even before rolling begins, swaddling needs to be done correctly. The wrap should be snug around the chest but loose enough at the hips that your baby can bend their legs up and out. Too-tight swaddling around the hips can contribute to hip development problems. Once you retire the swaddle, transition to a sleep sack with arm openings.
Pacifiers at Bedtime
Offering a pacifier when you put your baby down to sleep is associated with a lower risk of SIDS. The exact mechanism isn’t fully understood, but the association has appeared across multiple studies. If you’re breastfeeding, you can introduce a pacifier once nursing is well established, typically around two to four weeks. One study found that introducing a pacifier at 15 days for SIDS prevention did not affect breastfeeding rates at three months.
If the pacifier falls out after your baby falls asleep, you don’t need to put it back in. And if your baby simply won’t take one, don’t force it.
What to Avoid
- Car seats, swings, and bouncers for sleep. These are fine for their intended use, but babies shouldn’t sleep in them routinely. The semi-upright position can cause a baby’s head to fall forward, restricting the airway. If your baby falls asleep in a car seat during a drive, move them to a firm, flat surface when you arrive.
- Bed-sharing. This includes falling asleep with your baby on any shared surface, whether that’s a bed, couch, or recliner.
- Soft bedding of any kind. No matter how cold the room feels, the answer is warmer clothing on the baby, not blankets in the crib.
- Positioning devices. Wedges, positioners, and nests marketed to keep babies on their backs have not been shown to be safe and can themselves become suffocation hazards.
Safe infant sleep comes down to a simple formula: alone, on the back, on a firm flat surface, with nothing else in the sleep space. Every sleep, every time. The consistency matters as much as any single element.