No, it is not safe to place a baby on their side to sleep. Side sleeping is considered an unstable position that increases the chance an infant will roll onto their stomach, which carries the highest risk of sudden infant death syndrome (SIDS). The only recommended sleep position for infants is on their back, for every sleep, until their first birthday.
Why Side Sleeping Is Unsafe
The core problem with side sleeping is that it’s an in-between position. A baby placed on their side can easily roll face-down onto their stomach, and young infants lack the strength and coordination to reposition themselves or lift their head to breathe freely. Studies reviewed by the National Institutes of Health confirm that the side position is unstable and directly increases the likelihood of ending up in a prone (stomach-down) position.
When a baby ends up face-down, especially on soft bedding, a dangerous cycle called rebreathing can begin. The baby breathes in the same pocket of air trapped between their face and the surface beneath them. That pocket gradually loses oxygen and fills with carbon dioxide. Research published in the Journal of Applied Physiology found that the air closest to an infant’s face becomes the most oxygen-depleted, while fresher air sits farther away, out of reach of the baby’s small breaths. Although the body tries to compensate by taking deeper breaths, this is often not enough to overcome the problem, particularly in very young infants whose arousal reflexes are still developing.
What About Babies With Reflux?
Many parents worry that a baby sleeping on their back might choke on spit-up, and side sleeping can seem like a logical solution. This concern is understandable but not supported by evidence. Healthy babies have reflexes that cause them to swallow or cough up fluid, even while on their backs. SIDS rates dropped dramatically after back sleeping became the standard recommendation, with no increase in choking or aspiration incidents. Placing a baby on their side to prevent reflux-related problems actually introduces a greater risk than the one it’s trying to solve.
When Rolling Happens on Its Own
Once your baby can roll from back to stomach and from stomach to back independently, you can let them stay in whatever position they choose after you place them down on their back. Some babies begin rolling as early as 2 months, though most reach this milestone between 4 and 6 months. The key distinction is that the baby gets there on their own. A baby who can roll both ways has enough head and neck control to adjust their airway if needed.
Even after your baby starts rolling, always begin every sleep session by placing them on their back. You don’t need to stay awake monitoring them or flipping them back over once they’ve demonstrated the ability to roll in both directions.
Sleep Positioners and Wedges Are Dangerous
Products marketed to keep babies on their side or back during sleep, including bolster-style positioners and foam wedges, are not safe. The FDA has issued direct warnings against using them, citing multiple infant deaths over the years. Babies can suffocate after rolling from a side position onto their stomach within the device, or they can scoot upward or downward and become trapped between the positioner and the side of the crib or bassinet.
These products pose a suffocation risk regardless of whether they make medical claims or are labeled as “anti-reflux” or “SIDS prevention” devices. The safest sleep surface is a firm, flat mattress with nothing else in the crib: no pillows, no loose blankets, no stuffed animals, and no positioners of any kind.
Swaddling and Rolling Risk
Swaddling can be a helpful soothing tool for newborns, but it becomes a hazard once a baby starts trying to roll. A swaddled baby who rolls to their side or stomach has no way to use their arms to push up or reposition, making suffocation more likely. The American Academy of Pediatrics recommends stopping swaddling as soon as your baby shows any signs of attempting to roll, which can happen as early as 2 months.
If you want to continue using something for warmth or comfort after you stop swaddling, a wearable blanket or sleep sack that leaves the arms free is a safer alternative. Any product that compresses the arms, chest, or body should be discontinued once rolling begins.
Setting Up a Safe Sleep Environment
The simplest way to reduce sleep-related risks is to follow a few consistent practices every time your baby sleeps, whether it’s nighttime or a nap:
- Back position only. Place your baby on their back on a firm, flat surface designed for infant sleep.
- Bare crib. Use a fitted sheet and nothing else. Remove bumpers, blankets, toys, and positioners.
- Same room, separate surface. Room-sharing without bed-sharing for at least the first six months gives you proximity to monitor your baby without the risks of sharing a sleep surface.
- No soft surfaces. Avoid letting your baby sleep on couches, armchairs, or adult beds, even for short naps. These surfaces create pockets where air can become trapped near the face.
These guidelines apply to all infants, including preterm babies and those with reflux or other medical conditions. If your pediatrician has specific instructions for your baby’s situation, those take priority, but in virtually all cases, back sleeping on a firm surface remains the safest option.