Childhood asthma and smoking exposures before conception—A three-generational cohort study

Abstract

Background: Some human and animal studies have recently shown that maternal grandmother's smoking during pregnancy increases the risk of asthma in the grandchildren. We have investigated whether sex of the exposed parent and/or grandchild modifies the association between grandmaternal smoking and grandchild asthma. Methods: We formed a cohort study based on linkage of national registries with prospectively collected data over three generations. Smoking habits in early pregnancy were registered since 1982 and purchases of prescribed medication since 2005. In all, 10 329 children born since 2005 had information on maternal and grandmaternal smoking on both sides and were followed from birth up..