Exposure to particulate matter during pregnancy increases the risk of low birthweight and preterm birth

A new study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by ”la Caixa” Foundation, in collaboration with the Biomedical Research Networking Centre (CIBER), concludes that exposure to higher concentrations of particulate matter (PM2.5 and PM10) during pregnancy is associated with a significant reduction in birthweight and with a higher risk of preterm birth. These associations were stronger in babies whose mothers had a lower educational level, particularly when combined with residence in disadvantaged areas. The study results, published in the European Journal of Epidemiology, suggest that the third trimester of pregnancy may represent a critical window of susceptibility to PM10 in relation to birthweight.

Air pollution as a prenatal risk factor

Despite the policies implemented in Europe in recent decades to reduce air pollution, it remains one of the main environmental and public health challenges. During pregnancy, the foetus is particularly vulnerable to air pollutants – such as PM10 and PM2.5 –, as they can interfere with key developmental processes.

The study included data from more than 3.5 million births in Spain between 2004 and 2016 for PM10, and nearly 2 million births between 2010 and 2016 for PM2.5. The team estimated daily concentrations of particulate matter at the mothers’ home addresses throughout pregnancy using models that combined geographical data and artificial intelligence techniques. In addition, the data were stratified by maternal educational level as a socioeconomic indicator, allowing the assessment of potential inequalities in pollutant effects.

Exposure to PM10 may directly affect foetal growth

“For fine particles or PM2.5, the association with lower birthweight seems to be mainly due to an increased risk of preterm birth, that is, a shortening of gestational duration. In contrast, the effects of exposure to PM10 were not limited to this mechanism, suggesting that these particles may directly influence foetal growth,” explains Mònica Guxens, ICREA researcher at ISGlobal and first author of the study.

The third trimester, a critical window of susceptibility

The results indicate that the third trimester of pregnancy may represent a particularly vulnerable period to the effects of PM10 on foetal growth. The last two trimesters are key for foetal growth and maturation, when the demand for oxygen and nutrients rises considerably.

“Our findings highlight the need for policies to reduce particulate exposure among pregnant women, especially in socially vulnerable settings,” notes Mònica Guxens. “Future research should continue to explore the role of socioeconomic inequalities in exposure to pollutants, in order to design more equitable and effective public health interventions.”

Reference

Guxens, M., Botella, N., Stafoggia, M., Canto, M., Petricola, S., Valentín, A., Lertxundi, A., Fernández-Somoano, A., Freire, C., García-Altés, A., Diez, E., Marí-Dell’Olmo, M., Iñiguez, C., López, M. J., Ramis, R., & Binter, A.-C. (2025). Particulate matter exposure during pregnancy and birth outcomes: exposure windows of susceptibility and socioeconomic inequalities. European Journal of Epidemiology. https://doi.org/10.1007/s10654-025-01274-1