Lodge CJ, et al. - In this study, prospectively collected population-based data were analyzed to elucidate the link between grandmaternal smoking during pregnancy and the risk of asthma in grandchildren. Independent of maternal smoking, grandmaternal smoking during early pregnancy conferred an increased risk of asthma in grandchildren in the first six years of life. Essentially, this exhibited a dose-response relationship and was related to a persistent childhood asthma phenotype. The data support the possible epigenetic transmission of risk from environmental exposures in previous generations.