Summary: A new study reveals that prenatal exposure to common air pollutants like NO₂, PM2.5, and black carbon is associated with subtle but measurable changes in fetal brain structure during the second and third trimesters. Using specialized ultrasound scans, researchers found increased volumes in brain cavities, including the lateral ventricles and cisterna magna, and changes in areas related to motor coordination and sensory processing.
These effects were strongest in mid-to-late gestation, a critical window for brain development. While the differences fall within the normal range individually, they raise important concerns at the population level and highlight the urgent need to reduce prenatal exposure to pollution.
Key Facts:
- Brain Structure Changes: Pollutant exposure was linked to enlarged brain cavities and altered development in areas critical for motor control.
- Critical Timing: The strongest associations were seen in the second and third trimesters—key periods of fetal brain development.
- Population Relevance: Though individual changes were subtle, they carry significant implications for public health at scale.
Source: ISGLOBAL
Fetuses more exposed to certain air pollutants show changes in the size of specific brain structures, particularly during the second and third trimesters of pregnancy.
This is the main finding of a new study led by the Barcelona Institute for Global Health (ISGlobal), a center supported by the ”la Caixa” Foundation, in collaboration with the BCNatal center (Hospital Sant Joan de Déu, Hospital Clínic, and University of Barcelona) and the Hospital de la Santa Creu i Sant Pau.
It is the first study to specifically examine the association of air pollution on fetal brain development during pregnancy.
The study, published in The Lancet Planetary Health, analyzed data collected between 2018 and 2021 from 754 mother-fetus pairs participating in the BiSC (Barcelona Life Study Cohort) project in Barcelona.
This study aimed to understand the association of air pollution on child health and brain development, and is considered one of the most comprehensive studies in this field.
During the third trimester of pregnancy, participants underwent transvaginal neurosonography, a specialized ultrasound that allows the analysis of fetal brain shape and structures.
Exposure to nitrogen dioxide (NO₂), particulate matter (PM2.5), and black carbon was estimated with hybrid models that combine data from real measurements with advanced statistical methods.
The research considered three “microenvironments”: the participants’ homes, workplaces, and commuting routes. Data on activity patterns were collected via a geolocation app installed on the participants’ mobile phones.
The research team observed that prenatal exposure to NO₂, PM2.5, and black carbon in all aforementioned microenvironments combined was associated with an increase in the volume of various brain cavities that contain cerebrospinal fluid.
Specifically, direct associations were identified between exposure to these pollutants and increased volume of the lateral ventricles, located in each brain hemisphere, as well as an enlargement of the cisterna magna, a cavity located at the lower part of the brain.
An increase in the width of the cerebellar vermis —the central part of the cerebellum, essential for balance and motor coordination— was also detected.
The study results also showed an association between higher exposure to black carbon and a reduction in the depth of the lateral sulcus (also known as the Sylvian fissure), a deep groove that runs through the brain, which might suggest less maturation of the brain.
The associations between exposure to air pollution and changes in the morphology of these brain structures were stronger during the second and third trimesters of pregnancy.
“During mid to late gestation, the fetal brain enters a key phase of its development, making it particularly vulnerable to external factors such as pollution,” explains Payam Dadvand, ISGlobal researcher and a senior author of the study.
“As clinicians, we are now seeing compelling evidence that even in pregnancies that appear healthy by all conventional measures, factors such as air pollution can subtly affect fetal brain development.
“These findings underline the importance of increased awareness and education, both within the health community and across society,” say Elisa Llurba and Lola Gómez-Roig, clinicians at the Hospital de Sant Pau and BCNatal-Hospital Sant Joan de Déu, respectively, and co-authors of the study.
Significant Differences at the Population Level
The observed effects do not imply that the children participating in the BiSC project have pathological brain alterations. In fact, all measurements of the participants’ brain structures are within the range considered normal.
“The point is that these differences, although small at the individual level, are indeed relevant from a population perspective, as they inform us about how pollution affects the fetal brain and its vulnerability to environmental exposures,” says Laura Gómez-Herrera, ISGlobal researcher and co-lead author of the study.
The research team emphasizes the need for further studies to confirm these findings and track their potential consequences over time.
“At this stage, we can only report having observed differences in the brains of fetuses with higher exposure to pollution compared to those with lower exposure.
“Additional research is needed to determine whether these effects are reversible after birth or if they persist, and whether they have any implications for neurodevelopmental outcomes in later stages,” emphasizes Jordi Sunyer, a senior author of the study.
Despite the uncertainties that remain, this study could have significant implications for public health policy.
“Our findings strengthen the evidence supporting the need to reduce pregnant women’s exposure to air pollution, particularly in urban settings,” says Yu Zhao, ISGlobal researcher and co-lead author of the study.
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. Lancet Planetary Health
Abstract
Air pollution and foetal brain morphological development: a prospective study
Background
There is a scarcity of evidence of the influence of exposure to air pollution during pregnancy on the human fetal brain characterised prenatally. We aimed to evaluate the association of exposure to air pollution with fetal brain morphology.
Methods
In this prospective cohort study, we used data from the Barcelona Life Study Cohort, Spain, which recruited 1080 pregnant women at 8–14 weeks of gestation between Oct 16, 2018, and April 14, 2021, from three major university hospitals in Barcelona. Eligible participants were aged 18–45 years, had a singleton pregnancy, and had a fetus without major congenital anomalies. Third-trimester transvaginal neurosonography was applied to evaluate fetal brain morphological development.
We integrated comprehensive data on time–activity patterns with land use regression, dispersion, and hybrid models to estimate exposure to NO2, PM2·5, and black carbon at home, workplace, and commuting routes during pregnancy until the neurosonography date.
Single-pollutant linear mixed regression models and multipollutant ridge regression models were applied to estimate the associations between air pollutants and fetal brain outcomes, controlled for confounders. Distributed lag linear models were used to identify the vulnerable windows.
Findings
Among 1080 participants recruited at baseline, 954 attended the follow-up for the neurosonographic examination, 754 of whom were included in this study. In single-pollutant models, we found that prenatal exposure to NO2, PM2·5, and black carbon was associated with a wider anterior horn of lateral ventricles, wider cisterna magna, and larger cerebellar vermis. We also observed that higher exposure to black carbon was related to a shallower Sylvian fissure.
No clear pattern or associations were observed between air pollution and other structures of brain morphology. Multipollutant models showed that these associations with black carbon remained significant, whereas associations with PM2·5 and NO2 lost significance for some indicators. A potential vulnerability window in mid-to-late pregnancy was identified for these associations.
Interpretation
Exposure to air pollution might affect brain morphological development as early as the fetal stage. Our findings could have important policy implications as they highlight the need to mitigate exposure of pregnant individuals to air pollution in urban areas to protect fetal brain development.
Funding
European Research Council.
