Cotinine levels were especially high if infants slept with their parents or in colder rooms.
This may partly explain why sleeping with a parent is a known risk factor for sudden infant death syndrome (SIDS), say University of Leicester researchers.
For the study, cotinine levels were measured in the urine of 104 infants when 10-12 weeks old. Seventy-one babies had one or two parents who smoked, with each parent smoking an average of 16 cigarettes a day.
Infants from smoking households had average cotinine levels of 39mu g/mmol creatinine, compared with 5mu g/mmol in infants from smoke-free homes.
Maternal smoking was the largest single contributing factor, quadrupling cotinine levels in the infant. Paternal smoking at home doubled cotinine levels.
Having a baby sleep in the same room as a smoking parent increased cotinine levels more than fourfold. Low room temperature was a contributing factor.
The study also showed an association between seasonality and cotinine levels, aligning with the seasonal pattern of SIDS.
But preventing smoking in private homes requires education and willingness of the parent or carer, say the researchers.
- Arch Dis Child Fetal Neonatal Ed 2007 Online
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