NEW ORLEANS — Maternal smoking during pregnancy may exert a more powerful influence on asthma development in children than postnatal secondhand smoke or breastfeeding by smoking moms, researchers said here. Children of different ethnicities with exposure in utero to tobacco smoking were at nearly six times as likely to develop persistent asthma than children whose moms didn’t smoke during pregnancy, according to Sarena Apte, MD, of Case Western Reserve University in Cleveland. On the other hand, there no significant relationship between children’s asthma and mothers’ postnatal smoking status, Apte reported at the American Academy of Allergy, Asthma & Immunology annual meeting. Apte and colleagues analyzed data from 295 children, ages 8 to 16, who were participating in previous studies. Their parents provided information on their smoking habits during pregnancy and the first years of life in recent structured interviews. All the children were African American, Mexican-American, Mexican, or Puerto Rican, and lived either in the U.S. or in Puerto Rico. Persistent asthma was diagnosed in 194 of the children, with the remainder having intermittent illness.

In addition to the presence of persistent asthma, the researchers counted other significant symptoms such as wheezing, nocturnal symptoms, and daily symptoms. Apte and colleagues calculated the following odds ratios related to fetal exposure to smoking, relative to participants without such exposure:

This study was presented at the 2010 annual meeting of the American Academy of Allergy, Asthma, and Immunology in New Orleans