Co-sleeping broadly means sleeping in close proximity to your baby, but the term gets used in two very different ways, and the distinction matters. In medical settings, co-sleeping typically refers to room-sharing: your baby sleeps in their own crib or bassinet in your bedroom, but not in your bed. When most parents say “co-sleeping,” though, they often mean bed-sharing, where the baby sleeps on the same mattress as a parent. These are two very different arrangements with very different risk profiles.
Room-Sharing vs. Bed-Sharing
Room-sharing is when your baby sleeps in their own separate sleep space (a crib, bassinet, or bedside sleeper) within your bedroom. The American Academy of Pediatrics recommends this arrangement for at least the first six months of life, noting it can reduce the risk of sudden infant death syndrome (SIDS) by as much as 50%.
Bed-sharing is when your baby sleeps on the same surface as you, whether that’s a mattress, couch, or recliner. The AAP does not recommend bed-sharing under any circumstances, based on its review of the evidence. Despite this guidance, bed-sharing is extremely common. CDC data from 2015 found that 61.4% of mothers in surveyed states reported bed-sharing with their infant at least occasionally, with about 24% doing so often or always. Rates were highest among families who were breastfeeding at eight weeks postpartum.
Why Families Bed-Share
The most common reason parents bring their baby into bed is breastfeeding. Bed-sharing is strongly associated with longer breastfeeding duration within the first year. Mothers who bed-share tend to nurse more frequently at night, and the physical closeness makes nighttime feeds less disruptive. For exhausted parents, the practical appeal is straightforward: nobody has to fully wake up, get out of bed, and transfer a baby back and forth multiple times a night.
Cultural tradition also plays a role. Bed-sharing rates are higher among American Indian/Alaska Native, Black, and Asian/Pacific Islander families compared to white or Hispanic families. In many cultures worldwide, sleeping apart from an infant is the unusual practice, not the other way around.
The SIDS Risk With Bed-Sharing
The safety concern with bed-sharing centers on SIDS and suffocation. A large analysis of five major studies found that bed-sharing infants were 2.7 times more likely to die of SIDS than infants who room-shared in their own sleep space. For babies under three months old, the risk was notably higher: even when neither parent smoked, the baby was breastfed, and no other risk factors were present, bed-sharing at two weeks of age carried an 8.3 times increased risk compared to room-sharing.
That risk drops as babies grow. Bed-sharing remains a statistically significant risk factor through about the first 15 weeks of life, then declines. The absolute numbers are small either way. For low-risk families (nonsmoking, breastfeeding, no alcohol), the estimated risk of SIDS while room-sharing was about 0.08 per 1,000 live births, rising to about 0.23 per 1,000 while bed-sharing. That means the vast majority of bed-sharing babies in low-risk families are fine, but the relative increase is real.
Factors That Multiply the Risk
Certain factors turn bed-sharing from a modest risk into a dangerous one. Alcohol is the most dramatic amplifier. When a parent has consumed two or more drinks and bed-shares with a very young infant, the risk skyrockets to nearly 90 times that of a sober, room-sharing household. Alcohol impairs a parent’s ability to sense and respond to the baby’s position and breathing.
Smoking is similarly potent. When both parents smoke and the baby bed-shares, the risk of SIDS is 65 times higher than for a room-sharing, nonsmoking household. Any use of illegal drugs, including cannabis, increases the risk roughly 11-fold even when just room-sharing. Combined with bed-sharing, the risk becomes so large that researchers described it as essentially unquantifiable.
Falling asleep with a baby on a couch or armchair is considered dangerous in all circumstances, regardless of other risk factors. Soft bedding, pillows, and gaps between the mattress and headboard or wall also create suffocation hazards.
Harm Reduction for Families Who Bed-Share
Because so many families end up bed-sharing despite recommendations against it, some organizations have developed criteria to minimize risk for those who choose to do so. La Leche League International promotes what it calls the “Safe Sleep Seven,” a checklist for identifying lower-risk bed-sharing. The criteria specify a nonsmoking, sober mother who is breastfeeding, with a healthy baby placed on its back, lightly dressed, on a firm mattress with no gaps or cords, and with covers kept away from the baby’s head.
Meeting all seven criteria does not eliminate risk, but the research suggests it brings the absolute risk down to very low levels. The key message from harm-reduction advocates is that if you might fall asleep while feeding your baby, doing so in a prepared bed is far safer than nodding off in a recliner or on a sofa, where suffocation risk is substantially higher.
Bedside Sleepers as a Middle Ground
Bedside sleepers, sometimes called sidecar bassinets, attach to the side of an adult bed and give the baby their own firm sleep surface while keeping them within arm’s reach. This setup allows for easy nighttime breastfeeding without fully sharing a sleep surface. The Consumer Product Safety Commission finalized a mandatory safety standard for these products in 2023, requiring a barrier at least four inches high around the perimeter, secure attachment to the adult bed, and design features that prevent a baby’s neck from getting caught on the rail. If you’re using a bedside sleeper, make sure it meets ASTM F2906-23 standards and that the lowered rail sits at or below the height of your mattress.
Behavioral Outcomes in Children
Beyond the immediate safety question, some parents wonder whether co-sleeping affects a child’s development over time. A prospective study published in Behavioral Sleep Medicine tracked children who co-slept during early childhood (ages three to five) and found that co-sleeping at that age was associated with higher rates of internalizing behaviors like anxiety and depression, as well as externalizing behaviors like aggression, through preadolescence (ages 10 to 13). The predicted risk of withdrawal and depressive symptoms was more than doubled. These associations held even after researchers controlled for baseline behavior differences, and they were confirmed by reports from parents, teachers, and the children themselves.
It’s worth noting this research looked at co-sleeping that continued into early childhood, not at infants sharing a room with parents for the first several months. The study can’t prove co-sleeping caused these outcomes. Children who co-sleep longer may already have more anxiety or sleep difficulties that led to the arrangement in the first place. Still, the findings suggest that co-sleeping that persists well into the preschool years is worth paying attention to as a potential marker for behavioral concerns.
Practical Takeaways
The safest arrangement for the first six months is room-sharing without bed-sharing: your baby in a crib, bassinet, or bedside sleeper next to your bed, placed on their back on a firm, flat surface with no loose bedding. This setup keeps your baby close enough for nighttime feeds and monitoring while avoiding the suffocation risks of a shared mattress.
If you do bed-share, the risk is lowest when the baby is older than three to four months, both parents are nonsmokers, neither parent has consumed alcohol or sedating substances, and the bed is firm with no soft bedding near the baby. Never fall asleep with a baby on a couch, armchair, or waterbed. The single most important thing you can do is plan ahead: if there’s any chance you’ll fall asleep during a nighttime feed, set up your sleeping environment in advance so that if it happens, the conditions are as safe as possible.