NEW YORK (Reuters) -- Not only can cigarette smoke exposure increase an infant's risk of developing asthma, but smoking during pregnancy can have the same effect, a new study suggests.
The findings confirm that smoking is a preventable cause of asthma in young schoolchildren, and they "suggest that maternal smoking in pregnancy and current household exposure are independent contributors to this effect," reported lead study author Dr. Rodney Ehrlich in the American Journal of Respiratory & Critical Care Medicine.
In the new study, 368 children ages 7 to 9 who had asthma were compared to 294 children who did not. The researchers found that youngsters with eczema or who had a parent with asthma were about twice as likely to have the lung disorder. And those with hay fever were more than five times as likely to have asthma compared to other children, according to Ehrlich, of the department of community health at the University of Cape Town Medical School in South Africa.
Children whose mother smoked during pregnancy had 87% increase in the risk of asthma, and there was a 15% increase in risk for each additional smoker in the household.
It can be difficult to determine the effect of a mother's smoking during pregnancy as compared to that from smoking during the first year of the baby's life. However, in the study there was a greater asthma risk associated with those who smoked during pregnancy and after birth, compared to those who smoked after birth only.
"The findings are thus consistent with the hypothesis that there may be at least two mechanisms at work in the association between household or familial smoking and wheezing illness in young schoolchildren -- one operating in utero and the other postnatally," Ehrlich said.
Maternal smoking may change a fetus' airway size or functioning during gestation. That, in combination with smoke exposure after birth, may predispose children to wheezing in response to stimuli, such as allergic inflammation of the airways, Ehrlich said.
The children were exposed to high levels of cigarette smoke in the study. In this South African population, 58% of men and 59% of women smoked and the smoking rate during pregnancy was 44%.
"A substantial proportion of childhood wheezing illness in this population could thus be prevented by targeting smoking by mothers and other household members as a public health priority," Ehrlich concluded.
Asthma is characterized by wheezing, breathing difficulty, coughing and tightening of the chest, and can be potentially life-threatening in severe cases. Almost 10 million people in the United States have asthma and it is the most common cause of chronic illness in children.
SOURCE: American Journal of Respiratory & Critical Care Medicine (1996;154:681-688)
