Breathing Polluted Air During Pregnancy Increases the Risk of Having an Obese Child

Breathing air with high concentrations of pollution during pregnancy increases the risk of having a child who will suffer from overweight or obesity during childhood or adolescence. Specifically, the pollutant that constitutes the main risk factor for this health issue is suspended microparticles (PM2.5), a common component of urban and metropolitan atmospheric pollution generated by vehicle combustion (especially diesel) and other activities involving the burning of fossil fuels, such as heating or certain industrial processes.

This is the main conclusion reached by a European study led by the Barcelona Institute for Global Health (ISGlobal), a centre driven by the 'La Caixa' Foundation, which analysed over 30,000 families from eight countries, including Spain, to explore the links between daily exposure to major air pollution elements during gestation and childhood and the onset of overweight before the age of 13.

To conduct the study, researchers determined the concentrations of PM2.5 and Nitrogen Dioxide (NO3), the toxic gas emitted by exhaust pipes, at the residences of each of these families from the start of pregnancy until the child was 12 years old. They then cross-referenced these with the results of continuous clinical monitoring of these children. Throughout the children's childhood and preadolescence, their height and weight were monitored to observe the evolution of their body mass index (BMI).

The study's main finding is that when mothers breathed air with elevated levels of suspended microparticles during pregnancy, the risk of having children with overweight or obesity increased by 23%. These overweight episodes mainly manifested when the child was between 9 and 12 years old. However, there were no significant increases in obesity risk among children who lived in areas with high PM2.5 rates (but not their mothers during pregnancy) or among pregnant women and their children due to NO3 exposure. In summary, "our results indicate that the gestational period could represent a particularly vulnerable window for the risk of childhood obesity," states Sarah Warkentin, ISGlobal researcher and first author of the study.

"The biological mechanisms that can explain the relationship between exposure to air pollution and weight gain in children are not yet fully understood. In previous studies, exposure to pollution during pregnancy has been linked to reduced fetal growth and low birth weight. This may be due to oxidative stress, inflammation, placental development issues, or hormonal alterations. These same processes could also affect growth and increase the risk of obesity during childhood, as demonstrated in animal studies," explains Martine Vrijheid, director of the ISGlobal Life Environment and Health program and senior author of the study.