PurposeWe aimed to explore the effect of multiple pre- and postnatal exposures on optic nerve status in young adults due to this critical period for development. MethodsWe analysed peripapillary retinal nerve fibre layer (RNFL) status and macular thickness at age 18 years in the Copenhagen Prospective Studies on Asthma in Childhood 2000 (COPSAC(2000)) cohort in relation to several exposures. ResultsOf the 269 participants (median (IQR) age, 17.6 (0.6) years; 124 boys), 60 participants whose mothers had smoked during pregnancy had a thinner RNFL: adjusted mean difference -4.6 mu m (95% CI -7.7; -1.5 mu m, p = 0.004) compared with participants whose mothers had not smoked during pregnancy. A total of 30 participants who were exposed to tobacco smoke both during foetal life and childhood had thinner RNFL: -9.6 mu m (-13.4; -5.8 mu m, p < 0.001). Smoking during pregnancy was also associated with a macular thickness deficit: -4.7 mu m (-9.0; -0.4 mu m, p = 0.03). Higher indoor concentrations of particulate matter 2.5 (PM2.5) was associated with thinner RNFL: -3.6 mu m (-5.6; -1.6 mu m, p < 0.001) and a macular deficit: -2.7 mu m (-5.3; -0.1 mu m, p = 0.04) in the crude analyses, but not in the adjusted analyses. No difference was found among participants who smoked at age 18 years compared with non-smokers on RNFL or macular thickness. ConclusionsWe found that exposure to smoking during early life was associated with a thinner RNFL and macula at age 18 years. The absence of an association between active smoking at 18 years suggests that the vulnerability of the optic nerve is highest during prenatal life and early childhood.