How heat during pregnancy and in the first months of life can affect a child's brain development
A new study found a link between high temperatures in early life and slowed growth of the thalamus — one of the brain's key structures. Years later, this can manifest as behavioral characteristics in adolescence. EurekAlert introduces the details.
Climate change is leading to people worldwide increasingly facing temperature records, raising concerns about their impact on children's health. The period of pregnancy and the first years of life are especially important for brain development, as the brain grows particularly fast and is most sensitive to environmental influences during this time. While previous studies have already linked heat to changes in cognitive functions and mental health, its impact on brain structure has been studied much less.
A group of researchers from the Barcelona Institute for Global Health (ISGlobal) set out to investigate whether exposure to heat or cold during the period from conception to 8.5 years of age is linked to changes in brain development in late childhood and adolescence, and to identify periods when the brain is most vulnerable.
Scientists analyzed data from 3251 children participating in the Generation R Study — a Dutch birth cohort study. Using a climate model, they calculated average temperatures at participants' places of residence: weekly during pregnancy and monthly from birth to 8.5 years of age.
These data were then compared with the results of magnetic resonance imaging (MRI) scans performed on the children at approximately 10 and 14 years of age. This allowed them to assess how the volume of 11 brain structures changed and whether this process was related to previous exposure to heat or cold.
It was found that of all the structures studied, only the thalamus was consistently linked to heat exposure in early life. It is precisely the thalamus that processes and transmits sensory and motor information to the cerebral cortex.
The researchers suggest that this area may be particularly sensitive because it begins to form very early in pregnancy and develops according to a strictly defined schedule. In addition, during fetal development, the thalamus is intensely supplied with blood, which may make it more susceptible to changes that heat causes in the placenta or blood flow between mother and fetus.
️ Un nuevo estudio liderado por #ISGlobal sugiere que la exposición al calor durante el embarazo y los primeros meses de vida podría influir en el desarrollo cerebral infantil.
Los resultados refuerzan la importancia de proteger a embarazadas y bebés frente a las altas… pic.twitter.com/92IYN8Dt3H
Critical window: from conception to five months of life
According to the results of the study, the period from conception to the fifth month of a child's life after birth proved to be most sensitive to heat exposure. Compared to a reference average temperature of 12.5°C, exposure to average monthly temperatures of 20.5°C during this period (calculated taking day and night into account) was associated with slower thalamus growth between 9 and 15 years of age. Similar links were not found for other brain structures or for exposure to low temperatures.
The authors of the work note that the study does not allow for conclusions about the mechanisms of this influence. According to previous research, heat during pregnancy can affect placental function, maternal stress hormone levels, or serotonin signaling, which is important for forming connections between the thalamus and the cerebral cortex. Inflammation and oxidative stress may also play a role.
Researchers also found that slower thalamus growth was associated with more pronounced behavioral problems in adolescence, including aggression and a tendency to break rules. However, the study did not find a link between thalamus growth and cognitive abilities.
The authors note that future studies should clarify whether heat exposure during pregnancy and in the first months of life contributes to neurodevelopmental disorders and whether changes in thalamus development can explain this link. They also suggest that, as global temperatures continue to rise, measures to reduce heat exposure during this period may help protect children's brain development.
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