Pregnant women may need to take added precautions when it comes to air quality. A new study published in the journal Environment International has found that exposure to air pollution during pregnancy is associated with slower brain maturation in newborns — even within the first month of life.
The research, conducted jointly by scientists from Hospital del Mar, the Barcelona Institute for Global Health (ISGlobal) — an initiative supported by the “la Caixa” Foundation — and CIBERESP, is the first to analyse neonatal brain development at such an early stage.
The focus of the study was the process of myelination, which plays a crucial role in brain development. Myelination refers to the formation of a protective sheath (myelin) around nerve fibres, enhancing the speed and efficiency of neural communication. A delay in this process may signal impaired neurological development.
According to Dr. Gerard Martínez-Vilavella, researcher at the MRI Unit of Hospital del Mar, “Our study shows that the myelination process — a progressive indicator of brain maturation — occurs at a slower rate in newborns most exposed to PM2.5 during pregnancy.”
PM2.5 refers to fine airborne particles that are about 30 times smaller than the width of a human hair. These particles originate from combustion sources such as vehicle emissions, industrial processes, and biomass burning. While they may also contain essential metals like iron, zinc, and copper, their combination with toxic compounds makes them potentially harmful — particularly for developing foetuses.
The study followed pregnant women receiving prenatal care at three hospitals in Barcelona: Hospital Clínic de Barcelona, Hospital de la Santa Creu i Sant Pau, and Hospital Sant Joan de Déu. Air pollution exposure levels were tracked throughout their pregnancies. After delivery, 132 newborns underwent MRI scans within the first month to measure the extent of myelination.
The findings revealed a clear correlation between higher maternal exposure to PM2.5 and lower myelination levels in the infants’ brains.
“Air pollution, particularly PM2.5, is associated with changes in a fundamental mechanism of early brain development,” Dr. Martínez-Vilavella added. “It is imperative to better control pollution levels and examine the long-term implications of this delayed maturation.”
Dr. Jesús Pujol, head of the MRI Unit at Hospital del Mar, echoed this concern. “In early life, brain changes are dynamic and complex. Both delay and premature acceleration in maturation can be harmful. While we cannot yet say whether the observed effect is definitively detrimental, it highlights a new and important area of research.”
ISGlobal researcher Jordi Sunyer stressed the policy implications, noting that “even after the first phase of the low-emission zone policy in Barcelona, these findings suggest we must intensify efforts to reduce urban air pollution and comply with international air quality standards.”
The researchers concluded that no single pollutant within PM2.5 could be isolated as the cause. Instead, the cumulative effect of various components appears to be responsible for the observed delay in brain development.
