Sam Oh of the University of California, San Francisco, analyzed data from nearly 2,500 Latino and African-American young people.
The study, published in the Journal of Allergy and Clinical Immunology, found children of smokers had a 50 percent increase in uncontrolled asthma.
"Smoking during pregnancy only happens during the nine months," Oh said in a statement. "But we found the effects were still measurable eight to 17 years after the exposure."
Oh said he suspected chemicals from smoking changed something in the baby's genes while in the womb.
Women who smoke should quit before they become pregnant, Oh advised.
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