BERLIN (Reuters Health) - Italian researchers have found a possible explanation for why exposure to cigarette smoke during pregnancy may increase a baby's risk of sudden infant death syndrome or SIDS.

In a study presented here at the European Society of Cardiology annual conference, Professor Alessandro Mugelli from the University of Florence and colleagues found that exposing rats to carbon monoxide, a component of cigarette smoke, can interfere with the maturation of heart cells in the developing fetus. "We found that there is an alteration which may explain the link between smoking and SIDS, so the message is, don't smoke if you are pregnant, and don't smoke in a room where there is a baby," Mugelli said. The researchers exposed pregnant rats to carbon monoxide at a concentration of 150 parts per million, which simulates the levels experienced by a cigarette smoker. The exposure delayed the maturation of some properties in heart cells that affect the QT interval. The QT interval is one portion of an electrocardiogram, or ECG, the tracing of the heart's electrical activity. Babies who have a long QT interval have a higher risk of irregular heartbeats, and this may predispose these newborns to sudden death, Mugelli said. "We knew that smoking is a risk-factor for SIDS, but we didn't know the mechanism," Mugelli told Reuters Health. SIDS is the most common cause of death among newborns, Mugelli said. Placing a baby on his or her stomach rather than the back to sleep can greatly increase the risk of SIDS. Overheated rooms, secondhand smoke and fluffy bedding are also a risk.

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