Placing babies on their backs has cut cot death rates
The children of young mothers are at much higher risk of cot death because their parent misses out on prevention advice, a charity has warned.
Sudden infant death is five times more common in the babies of teenage mothers compared with older mothers, according to national figures.
The Foundation for the Study of Infant Deaths said smoking was the key factor.
A Canadian study showed babies whose mothers smoked in pregnancy struggled to cope with minor breathing problems.
Across the UK, there was a modest fall in cot deaths - where a child dies suddenly and unexpectedly in its first year - from 355 in 2005 to 321 in 2006.
However, the charity said the overall figures disguised a substantially bigger problem among teenagers.
In 2006, there were 58 deaths, a rate of 1.27 deaths for every 1,000 live births. Among the children of women aged over 35, the rate was just 0.23 per 1,000.
Chief executive Joyce Epstein said that key messages on smoking in pregnancy were not getting through: "It is totally unacceptable that the highest cot death rate occurs in the most disadvantaged groups.
"We are urging all healthcare professionals to make sure that the known life-saving advice reaches them."
She said that 100 cot deaths would be prevented if no women smoked in pregnancy.
The study published in the American Journal of Respiratory and Critical Care Medicine suggested that babies born early because their mothers smoked during pregnancy faced a even higher risk of cot death than those simply born prematurely.
Scientists from the Calgary Health Sciences Center compared the breathing responses of 22 babies, all of them born prematurely, half to non-smoking mothers, and half to smokers.
They were briefly given lower-than-normal oxygen levels to breath, to match the effects of breathing interruptions common in premature babies, and then watched to see how their bodies responded.
The blood oxygen levels in the babies of non-smokers recovered more swiftly than the other babies, whose increased heart rates suggested their bodies were under greater stress during this period.
Dr Shabih Hasan, who led the study, said: "This has clear implications for their risk of SIDS.
"Our study shows that pre-term infants make incomplete, or delayed recoveries from interruptions to breathing."
Ms Epstein said that the study might offer some clues about the underlying reason for some cot deaths.
She said: "It reinforces again the risk faced by babies of mothers who smoke.
"It is by far the biggest risk factor now that fewer babies are being put to bed on their fronts."