Should You Share a Bed With Your Baby? Why One of Humanity's Oldest Parenting Practices Is Now Controversial

When I asked Hadza mothers in Tanzania whether they would ever put a baby to sleep away from its mother, they looked at me as if the question itself made no sense.

Their reaction made me wonder whether the question had struck them as almost rude. How else would a mother protect a child through the night? How else would she keep her baby warm, nurse at the first stir, or remain close enough to detect danger?

Across much of the world—and, anthropologists argue, for much of human history—infant sleep has not been solitary. It has been social. Babies slept within a caregiver’s sensory radius: touching, smelling, listening, nursing, waking, and settling in a choreography older than cribs, electric light, and pediatric pamphlets.

That does not make bed-sharing automatically safe. Modern adult beds introduce soft mattresses, pillows, duvets, gaps, and elevated surfaces. The danger can rise further depending on the adult’s condition and the infant’s age and health. The old human pattern may be proximity. The modern risks often lie in the conditions under which that proximity occurs.

This may be an evolutionary mismatch: an ancient drive for closeness playing out in a sleep environment unlike the one in which it developed. Evolution cannot tell us that a practice is safe simply because humans have long practiced it. But paired with modern mortality research, it may help identify where the greatest dangers enter—and whether safe-sleep guidance can become more realistic without becoming less protective.

Why the Risks of Bed-Sharing Are Hard to Untangle

The safest recommendation is straightforward. Understanding how risk changes across real-world sleep environments is not. The American Academy of Pediatrics recommends that babies sleep on their backs, on a firm, flat, non-inclined surface, in the parents’ room but not in the parents’ bed, ideally for at least the first six months.

In 2024, the CDC recorded about 3,400 sudden unexpected infant deaths in the U.S.: 1,351 classified as SIDS, 1,099 as unknown causes, and 947 as accidental suffocation or strangulation in bed.

Some circumstances make sharing a sleep surface far more dangerous than others. Compared with parent-infant bed-sharing without additional hazards, the AAP estimates that risk rises more than tenfold when a caregiver’s alertness or ability to wake is impaired by fatigue, alcohol, drugs, or sedating medication; when the infant shares with a current smoker; or when the sleep surface is soft, such as a sofa or armchair. The risk rises five to tenfold for babies younger than four months or those sharing with another child or a nonparent. Prematurity, low birth weight, pillows, and loose bedding raise it two to fivefold.

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Teasing apart the contribution of each factor is difficult. Researchers cannot randomly assign babies to potentially dangerous sleep arrangements. They must rely on observational studies and death investigations, in which information may be incomplete and several hazards often overlap.

A 2024 Pediatrics study shows why the risks are so difficult to separate. Of the more than 7,500 infants whose deaths were examined, nearly 60 percent were sharing a sleep surface when they died. But because the study looked only at infants who died, that figure cannot tell us how risky surface-sharing is compared with sleeping separately. At least 76 percent of the deaths involved multiple unsafe conditions. Several dangers often overlapped, making it difficult to isolate the role of any one factor—including bed-sharing.

How Breastfeeding Complicates the Bed-Sharing Debate

Breastfeeding complicates the picture. It is associated with a lower risk of SIDS, yet it also brings mothers and babies into closer contact at night.

Helen Ball, an anthropologist at Durham University, has spent decades studying a distinction often lost in public debate: the difference between bed-sharing as a broad category and the specific circumstances that make it more dangerous.

In a 2016 study of 870 mothers in England who intended to breastfeed, Ball and colleagues tracked breastfeeding and bed-sharing for 26 weeks after birth. Among the 678 women with enough data to classify bed-sharing patterns, frequent bed-sharing was associated with breastfeeding at six months.

But the study could not determine causation: mothers who bed-shared often also expressed stronger commitment to breastfeeding before giving birth. Bed-sharing may help some mothers continue breastfeeding, but mothers already determined to breastfeed may also be more likely to bring babies into bed. That complicated relationship has led Ball and others to argue for risk minimization: tell parents the safest recommendation, but also explain what makes an unplanned or planned shared sleep situation far more dangerous.

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Biological anthropologist James McKenna approached the question by studying breastfeeding and infant sleep together. With Lee Gettler, he coined the term “breastsleeping” to describe a breastfeeding mother and infant who share a bed without other known hazards.

In a small 1997 laboratory study, bed-sharing breastfeeding infants fed more often and for longer during the night than solitary-sleeping infants. The study measured feeding behavior, not infant mortality risk. But it illustrated how feeding, infant arousal, maternal responsiveness, and sleep location form one biological ecology.

A study I conducted with Alyssa Crittenden and colleagues shows how ordinary shared sleep is among the Hadza. Of the 33 adults in the study, 30 reported sleeping in the same hut and on the same surface with at least one other person. Only three women were breastfeeding, too few to draw firm conclusions about how it affected their sleep. Across the full group, however, sharing with more sleepers was associated with shorter, more fragmented sleep. One mother, when asked why she slept with her infant, answered plainly: “This is my child so I can protect [them].”

That may help explain why shared infant sleep persists across cultures. But it cannot erase the risks of a modern bed. The harder question is what clinicians should tell parents who bed-share anyway, when the danger can vary so sharply depending on the infant, caregiver, and sleep environment.

How Countries Handle the Reality of Bed-Sharing

Public health authorities largely agree on the safest option: a separate, firm, flat infant sleep surface in the parents’ room. What differs is how they prepare families for the possibility that bed-sharing will happen anyway.

Unlike the AAP, the United Kingdom’s NICE and NHS guidance takes a more harm-reduction approach: they still say the safest place is a separate cot in the parents’ room, but they also advise families on how to reduce risk if bed-sharing happens and when it should be strongly avoided.

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New Zealand offers another response: its safe-sleep programs promote the wahakura, a traditional Māori woven bassinet, and the portable pēpi-pod. Both keep babies close while giving them a separate, protected surface.

The Choice My Family Made

Years after asking Hadza mothers whether a baby would ever sleep apart from its mother, I faced a version of that question in my own home.

I am an evolutionary anthropologist, not a clinician. I knew that a separate infant sleep surface was the safest choice. But my time with the Hadza and my familiarity with the work of Ball and McKenna had also helped me understand why breastfeeding and sleep can be difficult to separate.

By the sixth week of our first child’s life, my wife and I were beyond exhausted. She was also developing symptoms of mastitis amid the strain of having to wake fully for each nighttime feed: lights, positioning, latching, resettling, then the long drift back toward sleep. Our days narrowed into a fog of fatigue.

We eventually chose to share a bed with our baby. We tried to remove the known hazards and made the decision with the risks in view rather than wishing them away. We made the same choice with our second child. Our experience does not prove that the arrangement was safe or make it a recommendation for another family. But it helped me understand why families keep choosing it. For us, it was not an ideology. It was a way through the night.

The question, then, is not whether ancient mothers were right and modern doctors are wrong. It is whether current safe-sleep guidelines can become more precise and context-sensitive, without becoming less protective. Parents need a firm recommendation and an honest map of how the risk changes.

At night, a baby is never only sleeping. A baby is breathing, feeding, signaling, regulating, and depending on a caregiver’s body and judgment. The oldest human solution was nearness. Modern evidence tells us that nearness is safest when a baby has a separate sleep surface within reach. Good guidance should make that recommendation clear—and help parents understand the risks when their nights do not go according to plan.