While analyzing nearly 2,500 Latino and African-American children with asthma, a research team at UCSF found that children between age 8 and 17 with acute asthma symptoms were far more likely to have had mothers who smoked during pregnancy, even when the team controlled for elements such as education, socio-economic levels and childhood exposure to tobacco smoke.
“If women smoked while pregnant, their children had about a 50 per cent increase in uncontrolled asthma, even when we controlled for current tobacco exposure,” said Sam S. Oh, PhD, MPH, a postdoctoral scholar in epidemiology at the UCSF Center for Tobacco Research and Education, who is the first author in the paper.
“Kids who are 17 years old still show the effects of something they were exposed to during the first nine months of life,” he explained.
While extensive research has shown the effect of smoking on asthma risk in young children, the relative contribution of smoking during pregnancy has not been well established, with even less research focused on the populations that are more likely to use tobacco during pregnancy, according to the researchers.
The study found that the exact timing of tobacco exposure during pregnancy – whether it was the first trimester or third – was less important than whether they smoked at all, although children with acute symptoms were more likely to have had mothers who smoked for all nine months.
“Most mothers tend to quit smoking as pregnancy progresses, with the majority quitting by the end of the first trimester. But in African-American and Puerto Rican mothers, not only did they smoke more frequently, but they also smoked for a longer time during pregnancy,” Oh said.
The researchers said the findings highlight one of two possible causes: either the infant’s lungs are damaged during development in the womb or in the utero where exposure to tobacco smoke causes a genetic change that carries over to the next generation.
The results will appear in an upcoming issue of The Journal of Allergy and Clinical Immunology.