Babies should always sleep on their backs, on a firm and flat surface, with nothing else in the sleep area. That three-part rule, often shortened to “alone, on their back, on a flat surface,” applies to every sleep, including naps. The details beyond that basic framework matter too, from what your baby wears to bed to how long they should share your room.
The Back-Sleeping Rule
Place your baby on their back for every sleep, day and night, from the first day home. Back sleeping is the single most important thing you can do to reduce the risk of sudden infant death syndrome (SIDS). Some parents worry that babies will choke on spit-up in this position, but healthy infants have reflexes that clear their airway automatically.
Once your baby can roll from back to tummy and tummy to back on their own, you don’t need to reposition them if they flip during sleep. Until that milestone, always start them on their back.
All that time on their back can contribute to flat spots on the skull. The fix is supervised tummy time while your baby is awake. Aim for two or three short sessions of three to five minutes each day in the early weeks. By around two months, work up to 15 to 30 minutes of total tummy time daily. This builds neck and shoulder strength while giving the back of the head a break from constant pressure.
What Counts as a Safe Sleep Surface
A firm, flat mattress inside a safety-approved crib or bassinet, covered only by a fitted sheet, is the standard. Federal safety rules now require that any product marketed for infant sleep have a surface angled no more than 10 degrees from horizontal. At that near-flat angle, babies don’t slide or shift into positions that could block their airway.
Inclined sleepers, swings, bouncers, car seats, and lounging pillows are not safe sleep surfaces. Consumer Product Safety Commission data shows that the majority of deaths in these products happened after a baby rolled from their back onto their face. Some of these incidents involved babies as young as one month old. Extended use of inclined or poorly designed products has also been linked to flat head syndrome and twisted neck conditions. A crib, bassinet, or play yard with a firm mattress is the only place your baby should sleep unsupervised.
Nothing Else in the Crib
Keep blankets, pillows, stuffed animals, bumper pads, and any other soft bedding out of your baby’s sleep area. These items can cover a baby’s face and obstruct breathing. The sleep space should look bare. If you’re worried about your baby being cold, the answer isn’t a blanket. It’s what they’re wearing.
What Your Baby Should Wear to Bed
A wearable blanket, commonly called a sleep sack, is the safest way to keep your baby warm. Sleep sacks are rated using a system called TOG, which measures insulation. The lower the number, the lighter the fabric.
- Room above 71°F: a 0.2 or 0.3 TOG sleep sack (very lightweight)
- Room 67–75°F: a 1.0 TOG sleep sack
- Room 59–69°F: a 2.5 TOG sleep sack
- Room below 65°F: a 3.5 TOG sleep sack (the warmest option)
A good rule of thumb: dress your baby in one layer more than you’d be comfortable in. If the back of their neck or chest feels warm but not sweaty, the temperature is right.
When to Stop Swaddling
Swaddling can help calm newborns, but it becomes dangerous once a baby starts showing signs of rolling. If your baby is pushing up on their arms during tummy time, rocking side to side on their back, or has rolled even once in any direction, it’s time to transition out of the swaddle. A swaddled baby who rolls onto their stomach has no way to push up or clear their face. Most babies reach this stage somewhere between two and four months. Transition to an arms-free sleep sack at the first sign of rolling rather than waiting for a full back-to-tummy roll.
Room Sharing Without Bed Sharing
Your baby’s crib or bassinet should be 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 a different matter. Even in families where neither parent smokes and the baby is breastfed with no other risk factors, sharing an adult bed with a baby under three months carries roughly five times the SIDS risk compared to room sharing with the baby in a separate sleep surface. A large analysis published in BMJ Open found that after three months of age, the added risk of bed sharing dropped to statistically insignificant levels in low-risk families. But the risk climbs dramatically when other factors are present. If both parents smoke, bed sharing at two weeks of age raises SIDS risk 65-fold compared to room sharing with nonsmoking parents. Alcohol consumption before bed sharing pushes the risk even higher.
The safest setup is a crib or bassinet right next to your bed. You’re close enough to hear and reach your baby, but they have their own firm, clear surface.
Pacifiers at Sleep Time
Offering a pacifier when you put your baby down to sleep appears to cut SIDS risk roughly in half, based on pooled data from multiple studies. You don’t need to replace it if it falls out after your baby is asleep, and you shouldn’t force it if your baby refuses. If you’re breastfeeding, it’s generally recommended to wait until nursing is well established before introducing one, typically a few weeks in.
White Noise and Room Environment
White noise can help babies fall asleep and stay asleep, but volume and placement matter. Keep the sound machine at least seven feet from your baby’s sleeping space and set the volume no higher than 50 decibels, roughly the level of a quiet conversation. Running it louder or placing it right next to the crib can potentially affect developing hearing over time.
Room temperature between 68°F and 72°F is comfortable for most babies. A cool room with appropriate sleepwear is safer than a warm room, since overheating is an independent risk factor for SIDS.
How Much Sleep Babies Need
Newborns sleep 16 to 17 hours per day, but rarely more than one to two hours at a stretch. Their sleep cycles are short, and they wake frequently to eat. This is normal, even though it’s exhausting for parents. Between four and twelve months, total sleep drops slightly to 12 to 16 hours per day, and stretches of nighttime sleep gradually get longer. By around four to six months, many babies are capable of a longer block of sleep at night, though waking is still common and varies widely from baby to baby.
Naps remain important throughout the first year. Younger babies nap frequently in short bursts. As babies get closer to their first birthday, naps consolidate into two or three predictable daytime sleeps. Every nap follows the same safety rules as nighttime sleep: back, flat surface, nothing in the crib.