Asthma risk in children of minority mothers who smoked during pregnancy: Did quit time matter?

Objectives: Maternal smoking cessation prior to pregnancy is associated with reduced risk of childhood asthma. Since it is unknown whether smoking cessation during pregnancy has similar effects, the objective of this study was to investigate whether the time of smoking cessation during pregnancy within minority mothers reduces childhood asthma. Methods: Data from the 2007-2008 National Health and Nutrition Examination Surveys (a stratified, multistage probability sample of the U.S. population) was analyzed using logistic regressions to investigate whether the exposure, time of maternal smoking cessation during pregnancy had an effect on the outcome, childhood asthma. Confounding variables included race, income, presence of other household smokers, and mother's age at birth. Results: Of US mothers, 1,979,896 smoked during pregnancy. Approximately 27% had asthmatic children. About 26% stopped smoking in their first trimester, 16% in the second, and 3% in the third. Compared to women who did not stop smoking during pregnancy, women who stopped in the first (OR = 0.27; 95% CI = 0.09, 0.76) and second (OR = 0.47; 95% CI = 0.15, 1.47) trimesters were more likely to have asthma-free children. However, these associations were only significant in the first trimester. Conclusion: The associations between the time of smoking cessation and asthma was only established in the first trimester, due to small sample size and missing data on mothers who quit smoking in the third. Future research is needed to examine the associations in large-scale studies. Keywords: maternal smoking, asthma, smoking cessation, pregnancy