Bed sharing with parents is linked to a fivefold increased risk of sudden infant death syndrome (SIDS), even when the parents are non-smokers and the mother has not been drinking alcohol and does not use illegal drugs, according to a large analysis published online in BMJ Open.
While the rate of SIDS has fallen sharply following advice to parents to place babies to sleep on their back (supine), SIDS remains the major cause of infant death in the postneonatal period (28 days through to the first birthday) in developed countries.
Some countries, such as the Netherlands and the USA, advise parents not to sleep in the same bed as infants less than three months old, whereas others, such as the UK and Australia, advise only certain parents not to bed share with their young infants, including smokers and those who have been drinking alcohol or taking drugs.
The authors of this analysis estimate that around 88% of all SIDS deaths while bed sharing would not have occurred if bed sharing had been avoided. Their results show that even when neither parent smoked, and the baby was less than 3 months old, breastfed and the mother did not drink or take drugs, the risk of SIDS was five times higher than if the baby had slept in a cot next to their parents' bed.
The risk of SIDS while bed sharing decreased as the age of the infant rose, but if either parent was a smoker or the mother had drunk alcohol (two or more units in the last 24 hours) or used illegal drugs, including cannabis, at any time since the child was born, the risk was greatly increased.
Risks of bed sharing had been reported in different ways, so Professor Bob Carpenter, of the London School of Hygiene and Tropical Medicine, led this study which combined individual data from five published data sets from the UK, Europe and Australasia. It includes data on 1472 SIDS cases and 4679 controls and is the largest ever individual level study of the problem.
It revealed that one or both parents of 22.2% of the infants who had died from SIDS had been sleeping with their child at the time of death, while 9.6% of the parents in the control group had awoken the morning of the interview in the same bed as their child. Over the past 10 years, there has been a marked increase in bed sharing and the authors now estimate that around 50% of SIDS cases occur while bed sharing, more than double the figure found in the study.
The authors write: "88% of the deaths that occurred while bed sharing would probably not have occurred had the baby been placed on its back in a cot by the parents' bed." Even in very low-risk breastfed babies, where there were no risk factors for SIDS other than that they had slept in their parents' bed, 81% of SIDS deaths in infants under three months of age could have been prevented by not bed sharing, they add.
"The current messages saying that bed sharing is dangerous only if you or your partner are smokers, have been drinking alcohol or taking drugs that make you drowsy, are very tired or the baby is premature or of low-birth weight, are not effective," they say and call for recommendations "that take a more definitive stance against bed sharing for babies under 3 months".
"We do not suggest that babies should not be brought into the parent's bed for comfort and feeding. This has been investigated in previous studies and has not been found to be a risk factor, provided the infant is returned to his or her own cot for sleep," they write.
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Bed sharing when parents do not smoke: is there a risk of SIDS? An individual level analysis of five major case–control studies, Online First, doi:10.1136/bmjopen-2012-002299