Summary: A new prospective study finds that prenatal exposure to common urban air pollutants—nitrogen dioxide (NO2), fine particulate matter (PM2.5), and black carbon—is associated with subtle but measurable differences in fetal brain morphology during the second and third trimesters. Using detailed neurosonography, researchers observed enlarged cerebrospinal fluid spaces and alterations in regions involved in motor coordination and sensory processing.
These associations were most pronounced in mid-to-late pregnancy, a critical period for brain growth and organization. While each individual measurement remained within clinically normal ranges, the findings raise population-level concerns and underscore the importance of reducing pregnant people’s exposure to air pollution.
Key Facts:
- Structural changes: Higher prenatal pollutant exposure was linked to larger brain cavities that hold cerebrospinal fluid and to changes in structures tied to motor function.
- Timing matters: The strongest links appeared during the second and third trimesters, a vulnerable window for fetal neurodevelopment.
- Public health relevance: Effects are small on an individual level but could have important implications across populations exposed to urban air pollution.
Source: ISGLOBAL
Fetuses with greater prenatal exposure to common air pollutants show measurable differences in the size and shape of several brain structures, especially during mid-to-late gestation.
Led by researchers at the Barcelona Institute for Global Health (ISGlobal) with collaborators from BCNatal (Hospital Sant Joan de Déu, Hospital Clínic, and the University of Barcelona) and the Hospital de la Santa Creu i Sant Pau, this is the first study to evaluate prenatal air pollution exposure specifically against fetal brain morphology obtained during pregnancy.
Published in The Lancet Planetary Health, the study analyzed data collected from 2018 to 2021 as part of the Barcelona Life Study Cohort (BiSC). The analysis included 754 mother–fetus pairs who completed third-trimester neurosonography and had detailed exposure estimates.
Researchers used transvaginal neurosonography in the third trimester to measure fetal brain shape and structures with high resolution. Exposure to NO2, PM2.5, and black carbon was estimated using hybrid modelling that combined monitoring data, land use regression, dispersion models, and participants’ time–activity patterns. The team captured time spent at home, at work, and commuting via a geolocation app to improve exposure accuracy.
Across the combined microenvironments (home, workplace, commuting), higher prenatal exposure to NO2, PM2.5, and black carbon correlated with increased volumes of cerebrospinal fluid–filled cavities. Specifically, the study found associations with an expanded anterior horn of the lateral ventricles and a larger cisterna magna. The cerebellar vermis—the midline region of the cerebellum that supports balance and coordination—also tended to be wider in fetuses with greater exposure.
Notably, greater black carbon exposure was linked to a reduced depth of the lateral sulcus (Sylvian fissure), a major brain groove whose development reflects cortical maturation. These morphological changes were most evident during the second and third trimesters, when the fetal brain undergoes rapid structural and functional specialization.
“Mid to late gestation is a key phase for brain development, making the fetal brain particularly susceptible to environmental influences such as air pollution,” explains Payam Dadvand, ISGlobal researcher and senior author of the study. Clinicians involved in the research emphasize that these differences appear in otherwise healthy pregnancies, reinforcing the need for greater awareness about environmental risks during pregnancy.
Significance at the population level
All observed measurements remained within the clinically normal range, and the study does not indicate that participating children have pathological brain abnormalities. However, Laura Gómez-Herrera, the study’s co-lead author, notes that even small shifts in developmental markers can be meaningful when they affect large numbers of individuals across an exposed population.
The authors stress that additional research is needed to confirm these findings, to determine whether these prenatal differences persist after birth, and to assess their potential impact on later neurodevelopmental outcomes. “At this stage we report morphological differences associated with higher exposure versus lower exposure. Longitudinal follow-up is essential to understand reversibility or persistence and any clinical implications,” says Jordi Sunyer, senior author.
Despite remaining uncertainties, the study supports policy efforts to reduce pregnant people’s exposure to urban air pollution. “Our results add to the evidence base urging mitigation of air pollution in urban settings to protect fetal brain development,” says Yu Zhao, co-lead author.
About this neurodevelopment research news
Author: Èlia Pons
Source: ISGLOBAL
Contact: Èlia Pons – ISGLOBAL
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Air pollution and foetal brain morphological development: a prospective study” by Payam Dadvand et al. Published in Lancet Planetary Health (DOI: 10.1016/S2542-5196(25)00093-2)
Abstract
Air pollution and foetal brain morphological development: a prospective study
Background
Evidence is limited on how maternal exposure to air pollution during pregnancy affects the prenatally characterized human fetal brain. This study evaluates associations between prenatal exposure to urban air pollutants and fetal brain morphology assessed by neurosonography.
Methods
This prospective cohort used data from the Barcelona Life Study Cohort, which enrolled 1,080 pregnant women (8–14 weeks’ gestation) from three major university hospitals in Barcelona between October 2018 and April 2021. Eligible participants were 18–45 years old, carrying a singleton fetus without major congenital anomalies. Third-trimester transvaginal neurosonography measured fetal brain morphology. Researchers combined time–activity data with land use regression, dispersion, and hybrid models to estimate NO2, PM2.5, and black carbon exposure at home, workplace, and commuting routes up to the neurosonography date. Single-pollutant linear mixed models, multipollutant ridge regression, and distributed lag linear models were used to assess associations and identify vulnerable windows, controlling for potential confounders.
Findings
Of 1,080 recruited participants, 954 attended the neurosonography follow-up and 754 were included in this analysis. Single-pollutant models showed that prenatal exposure to NO2, PM2.5, and black carbon was associated with wider anterior horns of the lateral ventricles, larger cisterna magna, and increased cerebellar vermis width. Higher black carbon exposure was also related to a shallower Sylvian fissure. Multipollutant models indicated that associations with black carbon remained robust, while some associations for PM2.5 and NO2 attenuated. A vulnerability window in mid-to-late pregnancy was identified.
Interpretation
Air pollution exposure may influence brain morphological development beginning in utero. These findings have potential policy implications and support efforts to reduce pollution exposure among pregnant populations in urban areas to protect fetal brain development.
Funding
European Research Council.