Fetal tobacco exposure promotes asthma

Maternal smoking during pregnancy may exert a more powerful influence on asthma development in children than postnatal secondhand smoke or breastfeeding by smoking mothers, researchers said.
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 said these results add more force to recommendations that women stop smoking during pregnancy.
The study was one of several here suggesting that asthma risk is more closely linked to fetal exposures to chemical insults than exposures after birth.
Epidemiologic studies indicated that maternal folate levels during pregnancy, but not levels in infants themselves after birth, were related to subsequent asthma development.
Also, the plastics component bisphenyl A (BPA) has been reported to make mice more susceptible to experimental asthma when it was present in utero, but not in their mothers' milk after birth.
Session moderator Neil Alexis, PhD, an immunologist at the University of North Carolina who was not involved with Apte's study, said it was not surprising that exposures in utero should be more important than postnatal exposures.
"There's some evidence [from other research] that smoking in utero does alter the immune system at that critical stage of development," he said. "If you modify it at that point, things can go down a more allergic pathway."
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 said the research team planned to look next at genetic polymorphisms involved in tobacco processing, as well as whether the magnitude of the effects was related to the duration of smoking exposure.
She said it was impossible in this study to determine whether fetal or postnatal tobacco exposure had different effects in the ethnic groups represented in the study.
Asthma prevalence and severity is generally much greater among people of Puerto Rican background relative to Mexicans and Mexican-Americans, for example.
However, there were too few participants in each group to allow for meaningful comparisons, Apte said.

Source: Medpage Today, 01 March 2010