Exposure to fine particulate matter (PM2.5) during pregnancy may significantly increase the risk of childhood overweight or obesity, according to a major European study led by the Barcelona Institute for Global Health (ISGlobal), a center supported by the ”la Caixa” Foundation. The findings, published in Environment International, are based on data from over 37,000 mother-child pairs across ten birth cohorts in eight European countries.
The study, conducted as part of the EU-funded LifeCycle and ATHLETE projects, analyzed the impact of air pollution exposure during both pregnancy and childhood on body mass index (BMI) and obesity outcomes in children up to age 12. Researchers used geospatial models to estimate average annual exposure to nitrogen dioxide (NO₂) and PM2.5 at participants’ residential addresses.
The meta-analysis revealed that prenatal exposure to higher levels of PM2.5 was associated with a 23% increased risk of overweight or obesity in childhood, particularly in children aged 9–12 years. Notably, no significant associations were found between obesity and PM2.5 exposure during childhood, or exposure to NO₂ at any stage.
“These findings suggest that pregnancy may be a particularly sensitive period when it comes to long-term risk of obesity in children,” said Sarah Warkentin, ISGlobal researcher and lead author of the study. “More research is needed to better understand when during pregnancy the fetus is most vulnerable, and to confirm these results.”
Although the biological mechanisms remain unclear, previous research has shown that prenatal air pollution may impair fetal growth, potentially due to oxidative stress, inflammation, hormonal changes, or placental dysfunction. These factors could contribute not only to low birth weight but also to long-term risks like obesity.
The associations varied significantly among cohorts. For example, in the UK, prenatal and postnatal PM2.5 exposure was linked to a lower BMI, whereas in a Dutch cohort, childhood exposure to both PM2.5 and NO₂ correlated with higher BMI.
“This heterogeneity may reflect differences in pollution levels, urban environments, and children’s lifestyles across countries,” noted Martine Vrijheid, senior author of the study and director of ISGlobal’s Environment and Health over the Lifecourse programme. “Such variability underscores the importance of context when evaluating environmental health risks.”
Given that air pollution remains a widespread and preventable exposure, the study highlights the importance of cleaner environments—especially for expectant mothers—as a long-term investment in public health.
