Is co-sleeping safe for a baby aged 3 to 12 months?

What the evidence says

Bed-sharing means your baby sleeps in the same bed as you, instead of in their own crib or bassinet. Canadian health authorities, including Health Canada, the Public Health Agency of Canada, and the Canadian Paediatric Society, say bed-sharing is not advised at any age, though they explain that the danger is highest in the earliest months of life. The American Academy of Pediatrics gives similar advice: room-share, meaning baby's crib is in your room, but do not bed-share.

At the same time, some research looking back at real cases of Sudden Infant Death Syndrome, called SIDS, a sudden and unexplained death of a baby during sleep, has found that the risk connected to bed-sharing changes a lot with age. One large UK study found that when parents did not smoke, drink alcohol, use drugs, or sleep on a sofa with the baby, bed-sharing was not linked to a higher risk of SIDS once a baby passed about 3 months old, and the numbers even leaned toward being protective for older babies, though the group of babies studied was small.

What seems to matter most, across both guidelines and research, are specific dangerous situations. These include a parent who smokes, has been drinking alcohol or using drugs, is extremely tired, sleeping on a sofa or armchair with the baby, soft bedding like pillows or thick blankets, and a baby who was born premature or at low birth weight. These situations raise the risk sharply no matter the baby's age.

So for a baby between 3 and 12 months, official Canadian and American guidance still recommends room-sharing without bed-sharing as the safest choice. If a family does bed-share, knowing and avoiding the highest-risk situations listed above becomes especially important, and a firm, flat surface without soft bedding is safer than a soft mattress, sofa, or armchair.

Because the studies on this topic are observational, meaning researchers looked back at cases rather than running a controlled experiment, they cannot prove cause and effect the way a randomized trial could. This is part of why the guidelines take a cautious, avoid-it-altogether stance even though some data suggest lower risk for healthy older babies without other hazards present.