Children who are exposed to maternal smoking during pregnancy, but not in their first year of life, have an increased likelihood of developing wheeze and asthma at age 4 to 6 years, according to a study published online Aug. 17 in the American Journal of Respiratory and Critical Care Medicine.
Åsa Neuman, M.D., from the Karolinska Institutet in Stockholm, and
colleagues used pooled data from eight European birth cohorts involving
21,600 children to examine the effect of maternal smoking during
pregnancy on preschool age wheeze and asthma.
The researchers found that 735 children were exposed to maternal
smoking during pregnancy, but not in their first year. After adjustment
for sex, parental education, parental asthma, birth weight, and
siblings, maternal smoking during pregnancy correlated with wheeze and
asthma at age 4 to 6 years (adjusted odds ratio, 1.39 and 1.65,
respectively). There was a significantly increased likelihood of
developing wheeze and asthma in a linear dose-dependent manner, which
correlated with maternal daily cigarette consumption during the first
"Maternal smoking during pregnancy appears to increase the risk of
wheeze and asthma also among children who are not exposed to maternal
smoking after birth," the authors write. "Policy makers should be aware
of the important role of motivating tobacco smoking teenage girls and
young women to stop before getting pregnant to prevent asthma in their
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