News Release

Bed sharing leads to fivefold increase in risk of cot death for babies whose parents do not smoke

Peer-Reviewed Publication

London School of Hygiene & Tropical Medicine

Parents who share a bed with their breastfed baby could face a fivefold increase in the risk of cot death, even if the parents do not smoke, according to a new study. The research was led by the London School of Hygiene & Tropical Medicine and is published in BMJ Open.

Cot death – also known as sudden infant death syndrome (SIDs) – remains a major cause of death among babies under 1 year of age in high income countries. There is already a general consensus that sleeping with a baby increases the risk of cot death if the parents smoke or if the mother has been drinking alcohol or taking drugs. However, there are conflicting opinions as to whether bed sharing in general represents a risk when these factors are not present.

Some countries, including the US and the Netherlands, advise all parents against sharing a bed with their baby for the first 3 months. The UK currently only advises certain groups, including parents who are smokers, not to bed share.

The new study is the largest ever analysis of its kind. Researchers examined the individual records of 1,472 cot death cases and 4,679 control cases across five major studies. They found that the risk of cot death among breastfed babies under 3 months increased with bed sharing, even when the parents did not smoke and the mother had not consumed alcohol or drugs. This fivefold increase was in comparison to room sharing, where a baby slept in a cot in the parents' room.

The researchers estimate that 81% of cot deaths among babies under 3 months with no other risk factors could be prevented if they did not sleep in the same bed as their parents. The study also showed that the risk associated with bed sharing decreases as a baby gets older, and that the peak period for instances of cot death was between 7 and 10 weeks.

Professor Bob Carpenter from the London School of Hygiene & Tropical Medicine who was lead author on the study said: "Currently in the UK more than half of cot deaths occur while a baby is sleeping in the same bed as its parents. Although it is clear that smoking and drinking greatly increase the risk of cot death while bed sharing, our study shows that there is in fact an increased risk for all babies under 3 months who bed share, even if their parents do not smoke or drink.

"If parents were made aware of the risks of sleeping with their baby, and room sharing was instead promoted in the same way that the 'Back to Sleep' campaign was promoted 20 years ago to advise parents to place their newborn infants to sleep on their backs, we could achieve a substantial reduction in cot death rates in the UK. Annually there are around 300 cot death cases in babies under a year old in the UK, and this advice could save the lives of up to 40% of those. Health professionals need to make a definite stand against all bed sharing, especially for babies under 3 months."

The authors state that babies can still be brought into the parents' bed for comfort and feeding during the night, but that they should be placed in a cot next to the parents' bed to sleep.


For more information or to arrange interviews with Professor Carpenter please contact the London School of Hygiene & Tropical Medicine press office on +44 (0)20 7927 2802 or email

Notes to Editors:

1. R. Carpenter, C. McGarvey, EA. Mitchell et al. Bed sharing when parents do not smoke: is there a risk of SIDS? An individual level analysis of five major case-control studies. BMJ Open. doi:10.1136/bmjopen-2012-002299

2. Original data collection was funded by:

  • European Concerted Action on SIDS – The European Union and the Foundation for the Study of Infant Deaths;
  • Irish SIDS study – Irish Department of Health and Children;
  • New Zealand Cot Death Study – The Health Research Council of New Zealand;
  • Scottish Cot Death Study – Scottish Cot Death Trust;
  • German Study on Sudden Infant Death – Federal Ministry of Education and Research.

No additional funding was utilised for combining these datasets, imputing the missing data, analysis, or writing this report.

3. Annual cot death figures for the UK taken from Lullaby Trust report

About the London School of Hygiene & Tropical Medicine

The London School of Hygiene & Tropical Medicine is a world-leading centre for research and postgraduate education in public and global health, with 3,500 students and more than 1,000 staff working in over 100 countries. The School is one of the highest-rated research institutions in the UK, and was recently cited as one of the world's top universities for collaborative research. The School's mission is to improve health and health equity in the UK and worldwide; working in partnership to achieve excellence in public and global health research, education and translation of knowledge into policy and practice.

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