According to a new study, women who smoke while pregnant not only increase the risk that their children and grandchildren will develop asthma, but also that their great-grandchildren will face a higher risk for the sometimes deadly lung ailment. The findings come at a time when the number of asthma cases worldwide is climbing.
Experts have known for some time that women who smoke during pregnancy increase their non-smoking offspring’s and grandchildren's risk of developing asthma.
That’s because nicotine appears to make changes to DNA, creating a biological legacy, according to Virender Rehan, a neonatologist and biomedical researcher at Harbor-UCLA Medical Center in California.
“And we speculate.. on how nicotine might be affecting lung development in subsequent generations,” said Rehan.
Now comes the latest finding by Rehan and colleagues, suggesting expectant mothers who smoke also may transmit asthma to their non-smoking great-grandchildren.
In a study of pregnant rats, investigators gave the rodents daily injections of nicotine for almost three weeks until they gave birth.
A second group of pregnant rats received placebos or injections of an inactive substance. All of the rat pups were allowed to breast feed as much as they wanted before being weaned.
The young rats from the original mothers were then bred for up to three generations. At no time were any of these rodents exposed to nicotine.
Scientists next conducted a series of tests similar to those given to humans to diagnose the lung ailment. Rehan says the offspring of all of the rats exposed to nicotine showed signs of asthma.
“This is very well established that this is seen in the pups of the generation which is directly affected by nicotine. But the key findings of this study that we’ve taken not only the directly exposed generation, but to [the] subsequent generation and then [to the] subsequent generation.”
Experts say some 300 million people around the world suffer from asthma, a condition sometimes requiring emergency medical care when the airways become inflamed and swell rapidly in reaction to triggers including dust, pollen or medications, causing a serious narrowing of the airways. The number of asthma sufferers is expected to climb to 400 million by 2025.
An article on smoking’s effect on the great-grandchildren of pregnant women is published in the American Journal of Physiology-Lung Cellular and Molecular Physiology.