Overview

• Researchers analyzed 754 mother–fetus pairs in Barcelona between 2018 and 2021 using transvaginal neurosonography to map fetal brain morphology in the third trimester.
• Estimated exposure to nitrogen dioxide, PM2.5 and black carbon across home, workplace and commuting settings correlated with increased volumes of lateral ventricles, cisterna magna and cerebellar vermis.
• Associations were strongest during the second and third trimesters, pinpointing mid- to late-gestation as a critical window of vulnerability to air pollution.
• All observed brain measurements remained within normal ranges, though small population-level differences underscore potential public health implications.
• Authors call for longitudinal studies to verify these findings, assess whether changes persist after birth and guide policies to curb urban pollution exposure for pregnant women.