Blog
Exposure to air pollution during the prenatal period may slow down the development of a newborn’s brain
Oct
A new study from Spain shows that babies born to mothers exposed to higher levels of air pollution during pregnancy show signs of slower brain myelination, a subtle but telling change in the development of early brain connections.
Test: Uncovering the effects of prenatal air pollution on newborn brain maturation. Image source: PeopleImages/Shutterstock.com
A recent study published in suggests that prenatal exposure to air pollution is associated with delayed neonatal maturation, possibly related to a slowed rate of myelination.
Entry
The developing brain is very susceptible to damage from environmental factors, including air pollution. This can cause neuropsychiatric disorders, which are one of the leading causes of disability worldwide.
Particulate matter with a diameter of 2.5 µm or less (PM2.5) is often used as an indicator of pollution because it comes from many different pollution sources and contains a full spectrum of contaminants, including potentially toxic elements and essential trace metals such as iron, copper and zinc. It is easily inhaled and the particles can cross the blood-brain barrier, causing adverse effects on the brain.
Prenatal exposure to PM2.5 affects fetal development. Conversely, it exposes the fetus to essential micronutrients such as copper, iron, and zinc, all of which promote gestational myelination of white matter. Little is known about the effects of these contrasting exposures on the brain, reflecting the complex fetal response to pollutants.
For example, the offspring of women exposed to PM10 particulate matter had larger cerebral ventricles and cerebellums. The opposite was true for NO2 exposure, although both are pollutants. Opposite effects have been reported for other brain areas.
Myelination is an important marker of brain maturation. It involves the formation of myelin sheaths around the axons of neurons. The myelin sheath accelerates nerve conduction and shapes brain circuits. Myelination begins in the basic brain pathways and progresses to higher circuits, which is reflected in the development of an individual’s behavior.
Exposure to air pollution before birth causes changes in the white matter of the brain, including the content and structure of myelin. This led to the current study, which examined PM2.5 exposure during pregnancy as a predictor of neonatal brain myelination.
About the study
The study sample included 93 newborns born in three hospitals in Barcelona, Spain between 2018 and 2021. Their prenatal exposure to PM2.5 was modeled separately for the embryonic and late fetal phases. The newborn’s brain was imaged using magnetic resonance imaging (MRI) on day 29 of life after birth.
Research results
Infant age at MRI has been associated with brain volume and overall myelination, demonstrating the ability to record short-term neonatal brain development. However, this relationship was not found in the case of cerebral cortex myelination.
Increased prenatal exposure to PM2.5 in early pregnancy was associated with lower white matter content in the myelin cortex. In late pregnancy, this was associated with lower overall myelination. No associations with brain volume were found. This suggests that the cerebral cortex and deep white matter may respond differently to chemical contaminants in early stages of development.
This pattern was also observed for trace element exposure, although the associations weakened or disappeared after controlling for confounding factors.
The findings suggest a delay in early myelination after prenatal air pollution exposure. However, because myelination is a dynamic process whose rate varies with age, brain area, and food availability, this observation does not necessarily indicate harmful or lasting effects on the fetus.
In fact, one previous study indicates that children with higher cognitive skills have slower but more persistent white matter myelination. Apparently slower maturation occurred in the first year of life, with a catch-up phase occurring in the following year.
Again, the placenta can protect the fetus from certain pollutants, which at the same time allows the passage of essential elements.
Conclusions
Women exposed to air pollution during pregnancy gave birth to children with myelination of the lower part of the white matter in the neonatal period. Reduced cortical myelination was specifically associated with higher PM2.5 exposure in early pregnancy, but overall myelination decreased with later exposure. These findings suggest a potential delay in neonatal brain maturation.
No significant associations were found for iron, copper and zinc in PM2.5 particles, although the observed trends were in the same direction.
The authors noted that:
This study highlights the impact of environmental factors on newborn brain development and the importance of stringent air quality policies.
The cognitive effects of delayed neonatal white matter myelination remain unknown. Therefore, the study also highlights the importance of longitudinal research in understanding how prenatal air pollution affects long-term behavior and intellectual development.
