News / Health

Studies Show Maternal Smoking Triggers Asthma in Grandchildren

A woman smokes a cigarette in a parking lot in Bangkok, Thailand, May 27, 2010.A woman smokes a cigarette in a parking lot in Bangkok, Thailand, May 27, 2010.
A woman smokes a cigarette in a parking lot in Bangkok, Thailand, May 27, 2010.
A woman smokes a cigarette in a parking lot in Bangkok, Thailand, May 27, 2010.
Jessica Berman
Everyone knows that smoking cigarettes and other tobacco products is bad for your health... and for those around you. Now, there’s new evidence from studies with lab rats that the habit can cause asthma not only in smokers' children, but in their grandchildren, as well.

Researchers at Harbor-UCLA Medical Center in Los Angeles, California, have found evidence of a generational effect of tobacco-smoking on lung development. The scientists gave a group of pregnant rats injections of nicotine, the amount an average smoker would receive, exposing the animals' unborn pups to the chemical. Nicotine is one of more than 4,000 chemicals in tobacco smoke known to adversely affect lung development. As predicted, the injections caused changes in the fetal animals' upper and lower airway development consistent with asthma.  

The chronic and potentially fatal respiratory condition, which afflicts growing numbers of people worldwide, causes fits of coughing, wheezing, gasping and chest tightness.    

After they were born, the rat pups were never again exposed to nicotine. Nor were their offspring. Nevertheless, researchers found that these second-generation rat pups showed the same physical signs of asthma.
“So even if they are not exposed to any smoke or nicotine in the second generation pregnancy or [even] third generation pregnancy, they still go on to have asthma,” said neurologist Verinder Rehan, who led the study.

The change in lung function in the second generation of rat pups NOT exposed to nicotine in the womb was caused, Rehan said, by so-called epigenetic factors - alterations in how DNA functions as a result of environmental factors, such as the first generation’s exposure to nicotine.
The researchers saw what turned out to be a significant generational ripple stemming from the initial nicotine exposure.
“We have for the first time developed this experimental model where we are showing these changes actually happening... and we are also providing a mechanism that is the epigenetic mechanism responsible for these changes," said Rehand. "And actually even more importantly we have shown if you can block these changes, you can block the transmission of asthma.”

To demonstrate this, Rehan's group gave a separate group of rat mothers that had been injected with nicotine a drug that normalized their lung function. That healing prevented lung damage in two subsequent generations of pups.

Rehan said his study shows that the effects of cigarette exposure can be both far-reaching and long-lasting - another reason pregnant women should avoid lighting up or exposing themselves to second-hand smoke.
An article on the generational effects of nicotine exposure in causing asthma is published in BioMed Central's open access journal BMC Medicine.

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Comment Sorting
by: John Davidson
November 01, 2012 8:02 PM
In more rational times, before the anti-tobacco hysteria began in earnest, women who smoked continued to smoke and enjoy other normal pleasures of life without guilt during their pregnancies. Many even smoked during labor to help them relax and take the edge off their pain. If their doctors mentioned smoking at all, it would be to advise them to perhaps cut down if they were heavy smokers, something which most did intuitively because they didn’t “feel” like smoking as much.
But pity the poor Bolton smoker today who becomes pregnant, because she will be told that if she continues to smoke at all (or have any alcohol or caffeine) during her pregnancy, she is putting her developing fetus at high risk of death or disability.

Nothing could be further from the truth.

Though there is considerable evidence showing that on average the babies of women who smoke during pregnancy weigh on average a few ounces less than babies of women who do not smoke and that the rate of low birthweight babies is somewhat higher for smokers, there is no credible evidence for the hyperbolic claims that the babies of smokers have a higher mobidity and mortality rate. Quite the contrary, the babies of women who smoke during pregnancy have a better survival rate ounce for ounce, a somewhat lower rate of congenital defects, a lower rate of Down’s syndrome, a lower rate of infant respiratory distress syndrome and a somewhat lower rate of childhood cancer than do the babies of non-smokers.

Dr. Richard L. Naeye, a leading obstetrical researcher who studied more than 58,000 pregnancies, states unequivocally:

“We recently found no significant association between maternal smoking and either stillbirths or neonatal deaths when information about the underlying disorders, obtained from placental examinations, was incorporated into the analyses. Similar analyses found no correlation between maternal smoking and preterm birth. The most frequent initiating causes of preterm birth, stillbirth, and neonatal death are acute chorioamnionitis, disorders that produce chronic low blood flow from the uterus to the placenta, and major congenital malformations. There is no credible evidence that cigarette smoking has a role in the genesis of any of these disorders.”

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