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In the United States, smoking is the number one leading cause of preventable deaths. Smoking contributes to the development of several diseases such as lung cancer. Not only does smoking affect the smoker, it can also harm the health of those exposed to nicotine smoke. Several studies have researched the effects of such exposure on little children and even unborn fetuses. In a new study, researchers decided to examine a possible link between smoking during pregnancy and the risk of asthma across three generations. They discovered that women who smoked during pregnancy increased their great-grandchildren's risk of asthma.

The research team, headed by Virender K. Rehand and colleagues from the Los Angeles Biomedical Research Institute at Harbor - UCLA (University of California Los Angeles) Medical Center (LA BioMed) used mouse models to study the effects of maternal exposure of nicotine during pregnancy on great-grandchildren. The researchers created two separate groups of pregnant rats. In the first group, the researcher administered a dose of nicotine to the rats by injecting it under their skin every day. The injections started on the sixth day of pregnancy and lasted 21 days post birth. The babies were breastfed until they were weaned at three weeks. The injections were considered to mimic the effects of a daily human smoker. The other group went through the same procedure but received a placebo drug injection.

The researchers then had the new generation of mice breed. After the third generation was born, making them the great-grandchildren of the original set of mice, the researchers tested their lungs. They used a lung irritant to observe how narrow the mice's airways were, which would help indicate asthma. The researchers also used a chemical to test the mice's windpipes. The team discovered that the only rats that had indicators of asthma were the ones with the great-grandmothers who were exposed to nicotine.

The study's findings suggest that even after three generation, exposure to smoke during pregnancy could have lasting effects. Even though the study was done on mouse models, the results indicate that smoking can affect one's genetic risk of diseases.

The study, "Perinatal Nicotine-Induced Transgenerational Asthma," was published in the American Journal of Physiology-Lung Cellular and Molecular Physiology.