The safest way to lay a baby down to sleep is on their back, on a firm and flat surface, with nothing else in the crib. That single practice, recommended from birth through the first year, is the most effective way to reduce the risk of sudden infant death syndrome (SIDS). But the details matter: how you set up the sleep space, what you dress your baby in, and how you actually make the transition from your arms to the crib all play a role in both safety and how well your baby sleeps.
Always Start on the Back
Place your baby on their back for every sleep, including naps. This applies even to babies with reflux. Parents sometimes worry that a back-sleeping baby could choke on spit-up, but healthy babies naturally swallow or cough up fluids as a reflex. The National Institutes of Health notes that babies sleeping on their backs may actually be less likely to choke than those on their stomachs, because of how the airway is positioned relative to the esophagus.
If your baby has gastroesophageal reflux, the recommendation is still back sleeping on a flat surface. Propping up one end of the crib or placing the mattress at an incline is not effective at reducing reflux symptoms and creates a risk that your baby could slide into a position that restricts breathing.
Once babies can roll both ways on their own, typically around 4 to 6 months, you can let them find their own sleep position. But always start by placing them on their back.
Setting Up a Safe Crib
The crib needs three things: a firm, flat mattress that fits snugly inside the frame, a single fitted sheet, and nothing else. That means no blankets, no pillows, no stuffed animals, no bumper pads. The U.S. Consumer Product Safety Commission (CPSC) has connected 113 infant deaths to padded crib bumpers between 1990 and 2019, and the AAP has recommended against them since 2011. Mesh liners aren’t banned, but pediatricians advise skipping those too since they add risk without real benefit.
The mattress should have no gaps between its edges and the crib walls. If you can fit more than two fingers between the mattress and the side of the crib, the mattress is too small and poses an entrapment risk. Full-size crib mattresses are designed to fit standard cribs, but if you’re using a bassinet, play yard, or mini crib, make sure you’re using only the mattress that came with it or one specifically designed for that product.
Check hardware periodically. Tighten screws and bolts so nothing becomes loose over time. Never use a crib with missing or broken parts.
Room Sharing Without Bed Sharing
Keep 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, but bed sharing is a different story. Sleeping on an adult bed, couch, or recliner with a baby increases suffocation risk from pillows, blankets, and the possibility of an adult rolling onto the infant.
The room itself should stay between 62 and 68 degrees Fahrenheit (16 to 20 degrees Celsius). Overheating raises the risk of SIDS. To check if your baby is too warm, feel their stomach. It should be warm but not hot. Sweating, flushed cheeks, or damp hair are signs of overheating. Dress your baby in one layer more than you’d wear comfortably in the same room, and skip hats indoors since babies release excess heat through their heads.
Swaddling: When It Helps and When to Stop
Swaddling can help newborns sleep more soundly by dampening the startle reflex, that sudden arm-fling that wakes them up. A proper swaddle wraps snugly around the arms and chest while leaving the hips loose enough to bend and move freely. A too-tight wrap around the legs can cause hip problems.
The critical rule: stop swaddling when your baby shows signs of rolling. Most babies start showing these signs between 3 and 4 months. The telltale sign is when your baby can get their body up onto their shoulder, not just the involuntary newborn curl. Once a baby can roll onto their stomach, they need their arms free to push themselves up from the mattress. A swaddled baby face-down cannot do this.
If your baby is in that 3 to 4 month range but isn’t showing any rolling signs yet, you don’t need to preemptively stop. But the moment you see rolling attempts, it’s time to transition. Sleep sacks with arm holes are a good next step since they provide warmth without restricting arm movement.
The Drowsy but Awake Approach
One of the most effective habits you can build early is putting your baby down when they’re sleepy but not fully asleep. The idea is simple: if your baby always falls asleep in your arms, they’ll expect that every time they wake during the night. Babies cycle through light sleep stages frequently, and a baby who knows how to drift off independently will often resettle on their own instead of crying for you.
Watch for sleep cues like eye rubbing, yawning, fussiness, thumb sucking, or ear pulling. These signals tell you the window is open. Newborns can only stay awake for about 45 to 120 minutes between naps depending on their age, so the window can come quickly.
Try to separate feeding from falling asleep. If your baby routinely falls asleep at the breast or bottle, move the feeding to the beginning of your bedtime routine rather than the end. A short routine, even just a few minutes of dimmed lights and a quiet song, signals that sleep is coming and creates a consistent pattern your baby can learn to recognize. When your baby fusses after being put down, wait a few minutes before going in. If you do check on them, keep it brief: a gentle pat or tummy rub, then leave. Picking them up and rocking them back to drowsiness teaches them to expect that response at every waking.
This approach doesn’t always work perfectly, especially in the first couple of months when newborns fall asleep during feeds almost inevitably. That’s normal. The goal is to practice the skill over time, not to get it right every single time from birth.
Pacifiers at Sleep Time
Offering a pacifier when you lay your baby down is associated with a lower risk of SIDS. The AAP recommends pacifier use during sleep, with one caveat: if you’re breastfeeding, wait until nursing is well established (usually around 3 to 4 weeks) before introducing one. The protective mechanism isn’t fully understood, but researchers believe pacifier use during sleep may help maintain better breathing patterns and keep the airway open.
If the pacifier falls out after your baby is asleep, you don’t need to put it back in. And if your baby doesn’t want it, don’t force it. The benefit comes from the initial placement at sleep onset.
Putting It All Together
The actual moment of laying your baby down works best as the final step in a short, predictable sequence. Feed your baby, do a brief calming routine (a diaper change, a song, dimmed lights), then place them on their back in the crib while they’re drowsy. Their sleep space should have nothing in it but the fitted sheet. The room should be comfortably cool and dark or dim. If your baby is under 3 to 4 months and not yet rolling, a snug swaddle can help them settle. After that age, a wearable sleep sack keeps them warm without loose fabric.
Lay your baby with their feet near the bottom of the crib so they can’t shimmy down under any fabric. Lower them gently, keeping one hand on their chest for a moment after their back touches the mattress. That brief pressure and warmth can ease the transition from being held. Then step back, and give them a chance to settle on their own.