Luyten LJ, Dockx Y Provost EB, et al. - Considering that in utero exposure to particulate matter may entail adverse health outcomes later in life, researchers here examined if prenatal or postnatal exposure to PM_2.5 (particulate matter with a diameter ≤ 2.5 μm) or NO₂ is related to microvascular traits in children between the age of four and six. Young children (mean [SD] age 4.6 [0.4] years), followed longitudinally within the ENVIRONAGE birth cohort, were assessed for the retinal microvascular diameters, the central retinal arteriolar equivalent and central retinal venular equivalent, and the vessel curvature by means of the tortuosity index. For each participant’s home address, daily prenatal and postnatal PM2.5 and NO2 exposure levels were assessed using a high-resolution spatiotemporal model. Analyses suggest that a higher maternal exposure to PM_2.5 and NO₂ during the entire pregnancy period results in widening of retinal venular and arterial diameters of children. Further, they suggest that in utero exposure to NO₂ for the entire pregnancy and the third trimester affects the retinal blood vessel curvature, represented by an increase in tortuosity index. This study is identified to be the first work demonstrating a correlation between air pollution exposure during gestation and effects on the retinal microvasculature later in life.