A third of all deaths from Sudden Infant Death Syndrome or "cot death" could be eliminated if expectant mothers avoided smoking, and fathers and everyone else stopped puffing around them, during pregnancy.
This finding comes out of a recent study by Sweden's Karolinksa Institute published in the journal Hypertension, reports the BBC America.
Doctors have known for a long time that smoking is harmful to a developing fetus. They've also known that SIDS is largely a cardiovascular issue.
But now they strongly suspect that it's not just related to breathing but to blood pressure and the health of the baby's heart.
Babies of moms who smoked or were exposed to secondhand smoke during pregnancy tend to have abnormal heart rate and blood pressure responses that actually get worse during the first year of life outside the womb.
This greatly increases the chances that a baby will die in his sleep -- even when he is sleeping with unobstructed airways. A lot of moms of babies who die of SIDS often blame themselves for doing this or that, that if they only changed one thing their baby might still be alive.
But more and more, experts believe that SIDS is not due to one but several different risk factors, cigarette smoking included, that combined create a sort of perfect storm of health problems.
Experts strongly suggest babies sleep on their backs partly because it gives children with an already compromised cardiovascular system a better chance at making in through that first year of life, the time when the risk for SIDS is highest.