Tobacco smoke exposure in utero and during early childhood can affect children's lung function Environmental tobacco smoke exposure in utero and during early childhood-;especially secondhand smoke-;is associated with decreased childhood lung function, according to research presented at the ATS 2021 International Conference. Hanna Knihtilä, MD, PhD, research fellow, Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, and colleagues sought to clarify the effects of tobacco smoke exposure during pregnancy and childhood on children's lung function at age six years. The authors found that cumulative tobacco smoke exposure reflected by increased blood cotinine levels during pregnancy and childhood is associated with decreased lung function at six years of age. This decrease is evident even with minimal smoking exposures.