Pregnancy and child

Sharing a bed with your baby ups risk of cot death

"Bed-sharing 'raises cot death risk fivefold'," BBC News reports. The news has featured in much of the media, with headlines based on a large analysis of previous studies into the risk of cot death, or sudden infant death syndrome (SIDS), associated with bed-sharing.

Bed-sharing is where babies sleep in the same bed as their parents. It has long been known that bed-sharing with a parent who smokes or has consumed drugs or alcohol increases the risk of SIDS.

This new study aimed to see if bed-sharing still increased the risk of SIDS in the absence of these risk factors.

The researchers found a fivefold increase in the risk of SIDS associated with bed-sharing in breastfed babies who were under three months old, had parents who did not smoke, and when the mother had not had any alcohol or drugs.

The risk of SIDS was even higher when the parents smoked, drank or used drugs.

It is important to note that the researchers did not conclude that babies should not be brought into their parents' bed for comfort and feeding, only that they should not sleep in the same bed as their parents.

It is also important to be aware that the overall risk of SIDS is very small and it is a rare condition. However, there are simple steps parents can take to reduce the risk of SIDS (see box), and it is well worth following this potentially life-saving advice.

Where did the story come from?

The study was carried out by an international team of researchers from the London School of Hygiene and Tropical Medicine, the University of Glasgow and the Medical Research Council, UK; the Children's University Hospital, Ireland; the University of Auckland, New Zealand; and the University of Muenster, Germany.

No external sources of funding were reported, although the original research this report is based on was funded by a number of governmental bodies, charities and trusts.

The study was published in the peer-reviewed open access medical journal, BMJ Open.

The story was well reported by the media. 

What kind of research was this?

This study combined information from individuals in five large case-control studies. These studies had collected data on babies who died from SIDS (cases) and babies of a similar age who were still alive (controls).

The researchers were interested in bed-sharing specifically. The research aimed to resolve the uncertainty over whether there is a risk of SIDS associated with bed-sharing in breastfed babies where neither parent smoked. 

What did the research involve?

The researchers combined individual data from studies in the UK, Europe and Australasia. In total, information was collected for 1,472 babies who died from SIDS and 4,679 control infants, all under one year of age. Control infants were randomly selected normal infants of a similar age, from a similar location and born at a similar time.

The researchers estimated the risk associated with bed-sharing in relation to breastfeeding, smoking, and the mother's recent alcohol consumption or illegal drug use. This was after they had controlled for other important risk predictors, including:

  • whether the baby slept in the parents' room or elsewhere
  • the position in which the baby was put to sleep
  • mother's age
  • mother's relationship status
  • the number of children the mother had had previously
  • the baby's birth weight

What were the basic results?

The researchers found that 22.2% of cases and 9.6% of controls reported a history of bed-sharing. Bed-sharing increased the risk of SIDS fivefold (adjusted odds ratio [OR] 5.1, 95% confidence interval [CI] 2.3 to 11.4) compared with room-sharing (assuming the baby was placed on his or her back in a cot in the parents' room) when:

  • neither parent smoked
  • the mother did not drink
  • the baby was less than three months old
  • the baby was breastfed, and
  • there were no other risk factors

The researchers estimate that the absolute risk of SIDS for room-sharing infants was 0.00008 (eight per 100,000) when neither parent smoked and the baby was less than three months old, breastfed, and had no other risk factors.

Bed-sharing increased the absolute risk of SIDS by 0.15 per 1,000. This means the absolute risk from bed-sharing was 0.00023 (0.23 per 1,000).

Bed-sharing, smoking and alcohol use all increased the risk of SIDS. However, the risks associated with bed-sharing decreased as the baby got older.

How did the researchers interpret the results?

The researchers concluded that, "Bed-sharing for sleep when the parents do not smoke or take alcohol or drugs increases the risk of SIDS. Risks associated with bed-sharing are greatly increased when combined with parental smoking, maternal alcohol consumption and/or drug use. A substantial reduction of SIDS rates could be achieved if parents avoided bed-sharing."


This large case-control study combined information from five studies to investigate the risk of sudden infant death syndrome (SIDS) associated with bed-sharing.

It found that bed-sharing is associated with a fivefold increase in the risk of SIDS compared with room-sharing for babies who were less than three months old, breastfed, sharing with non-smoking parents, and the mother had not had alcohol or drugs.

Smoking, alcohol and drug use are already recognised risk factors for SIDS and greatly increase the risk associated with bed-sharing.

The researchers have not concluded that babies should not be brought into the parents' bed for comfort and feeding. Rather, they advise that babies should not sleep in their parents' bed. It is also worth highlighting the very small actual risk of SIDS, both for non-sharing and bed-sharing babies.

Although this study was appropriately designed and controlled for, a number of potential factors that could affect the risk of SIDS and the causes of SIDS are not firmly established. This means that there may be other factors responsible for the observed increase in risk associated with bed-sharing.

To decrease the risk of SIDS, current advice recommends:

  • putting your baby to sleep on their back – the safest place for them to sleep is in a cot in a room with you for the first six months
  • do not smoke
  • do not share a bed with your baby, particularly if you have been drinking or have taken drugs
  • never sleep with your baby on a sofa
  • do not let your baby get too hot and keep your baby's head uncovered
  • if possible, breastfeed your baby

NHS Attribution