The likelihood applies even if parents are not smokers, drinkers, or drug users - other factors that raise the risk of SIDS, according to the study led by the London School of Hygiene & Tropical Medicine.
A previous study conducted by a research team at the University of Calgary, Canada, suggests that premature infants born to mothers who smoke are at a higher risk for SIDS than premature babies born to non-smokers.
SIDS, also called cot death in the UK, is one of the major causes of death among infants under the age of 1, mainly in high-income nations.
Past research established that the risk rate of SIDS increased when parents were sleeping with the newborn and were smokers, drinkers, or using drugs, but it was not clear whether this result was the same if parents did not have these habits.
In the UK, current recommendations say that parents should pick where their baby sleeps, however, the safest option is in a crib or cot in the same room.
The study was one of the largest of its kind and analyzed individual records of approximately 1,472 SIDS deaths and 4,679 control cases across five studies.
The investigators found that the risk of SIDS was more frequent in breast-fed babies younger than 3 months who shared the bed with their parents, even if the parents did not use alcohol, drugs, or smoke cigarettes.
The authors suggest that close to 81% of SIDS deaths among babies under three months with no risk factors could have been prevented if they had not shared a bed with their parents.
Additionally, the risk of bed-sharing decreased as the infant got older. The most prevalent period for the occurrence of SIDS was between 7 and 10 weeks.
A study published in Pediatrics suggests that bed-sharing with toddlers does not increase the risk of learning or behavioral problems, however, they say the risk of SIDS is still possible and should be considered when choosing sleeping position and location.
Lead author of the current study, Professor Bob Carpenter from the London School of Hygiene & Tropical Medicine said:
"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. 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 indicate that a significant decrease in SIDS rates could be reached if parents did not share beds with their babies. The Netherlands and the U.S. are two of the few nations that recommend parents do not share a bed with their baby in the first three months after birth.
Other research claims that breastfeeding reduces the risk for SIDS by up to 73%.
Written by Kelly Fitzgerald