The study shows that cotinine, a chemical released when the body breaks down nicotine, is more abundant in urine samples from smokers' babies than from nonsmokers' children.
It's not clear how cotinine levels affect babies, but exposure to tobacco smoke isn't healthy, note the researchers, who included Mike Wailoo, M.D., FRCP, a senior lecturer in the child health department of England's University of Leicester.
Wailoo and colleagues analyzed urine samples from 104 babies who were about 10-12 weeks old.
Most of the babies — 68% — had at least one parent who smoked cigarettes. Overall, 62% of the babies had mothers and fathers who smoked. Eighteen percent only had a mother who smoked. The remaining 20% only had a father who smoked. Those parents smoked 16 cigarettes per day, on average.
The babies of parents who smoked had cotinine levels that were more than five times higher than babies of nonsmoking parents.
Maternal smoking had the biggest effect, quadrupling the babies' cotinine levels. Paternal smoking nearly doubled the babies' cotinine levels.
"Our findings clearly show that by accumulating cotinine, babies become heavy passive smokers secondary to the active smoking of parents," write the researchers.
They note that it's up to parents to decide not to smoke around their children. "The well-recognized maternal desire to protect the child is the great hope for the future," Wailoo's team writes.
By Miranda Hitti
Reviewed by Louise Chang, M.D.
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