Exposure to smoking (both maternal smoking during pregnancy and second-hand smoking during childhood), air pollution, as well as certain characteristics of the built environment may be associated with a higher development of obesity in children, according to a recent study. The authors used data on body mass index (BMI), waist circumference, skinfold thickness and body fat mass to determine the children's overweight and obesity status. Blood and urine samples from the children and their mothers during pregnancy were also analysed. In total, 77 pregnancy and 96 childhood exposures were assessed, including air pollutants, built environment, green spaces, smoking, and chemical pollutants (persistent organic pollutants, heavy metals, phthalates, phenols and pesticides. The findings of the study, which used data collected before anti-COVID-19 measures were introduced, were in line with global trends: the combined prevalence of overweight and obesity was 29% for the study population as a whole, with higher percentage. The results showed that exposure to smoking (both maternal smoking during pregnancy and second-hand smoking during childhood), air pollution (PM2.5 and PM10 particulate matter and nitrogen dioxide, indoor and outdoor) as well as certain characteristics of the built environment were associated with a higher childhood BMI. Differences in socioeconomic status did not explain these findings.