Heatwaves During Pregnancy Could Affect Baby's Brain Development, Study Suggests

Key TakeawaysNew research suggests that children who were exposed to hot days during gestation and infancy might be at increased neurological riskHeat exposure appeared linked to slower growth during childhood of a key brain center, the thalamusSlowed thalamic growth has been tied to more problematic 'acting out' during the teen years.THURSDAY, July 16, 2026 (HealthDay News) — Climate change could be increasing risks to children's brain development. A new study finds that exposure to higher temperatures during pregnancy could spur neurological changes in infancy and beyond.These potentially detrimental changes to the brain occurred within the thalamus, a neurological center for information processing and the regulation of sleep, alertness and consciousness."Future studies should investigate whether early-life heat exposure contributes to neurodevelopmental disorders and whether altered thalamic development could help explain these associations," said study co-author Esmée Essers, a researcher at the Barcelona Institute for Global Health, in Spain.Her team's study involved data on 3,251 Dutch children. All were part of a long-term study that began in 2002 and tracked their growth, health and development from the womb into adulthood. "We wanted to examine whether exposure to heat or cold from conception to 8.5 years of age was associated with changes in brain development during late childhood and adolescence, and to identify the periods when the brain is most vulnerable," explained lead author Laura Granés, who is also a researcher at the Barcelona institute. The research team employed a special "climate model," which tracked weekly outdoor temperatures during each child's gestation, as well as monthly temperature estimates during infancy and up to 8.5 years of age.They then compared those temperature ups and downs to any changes observed in 11 different brain centers. They looked especially at MRI brain scans taken of each child at ages 10 and 14.Only the volume of the thalamus appeared linked to exposures to high heat during gestation or infancy, the Spanish team found.As they explained, the thalamus develops very early in pregnancy and requires a robust blood supply, which may make it especially vulnerable to higher temperatures. Exposure to hot days may affect blood flow to the placenta and/or fetus, the researchers said.Specifically, fetal and infant exposures to average monthly temperatures of about 69 degrees Fahrenheit (averaged over days and nights) was linked to slower thalamic growth between 9 and 15 years of age, compared to kids who had been exposed to monthly temperatures averaging 54.5 degrees F during the same stages of development.Why would outside temperatures make such a difference? The authors theorize that hot days may raise maternal stress hormone levels, while at the same time limiting the placenta's ability to shield the fetus from these hormonal changes. High heat might also impair the activity of the neurotransmitter serotonin. This chemical messenger helps forge connections between the fetal/infant thalamus and the brain's cerebral cortex, they said.All of this could impact a child's neurological development years later, because slowed thalamic growth has been linked to externalizing behavioral symptoms during adolescence, "including aggressive and rule-breaking behavior," according to an institute news release. No connection between slowed thalamic growth and cognitive performance was observed, however.The new findings may be valuable, as global warming spurs more severe and lengthy heatwaves worldwide."With global temperatures continuing to rise, to reduce heat exposure during pregnancy and early infancy could play an important role in protecting children's brain development," said study coordinator Mònica Guxens, a research professor at the institute.The findings are published in the August issue of the journal Environment International.More informationFind out more about the thalamus at the Cleveland Clinic.SOURCE: Barcelona Institute for Global Health, news release, July 13, 2026 .What This Means For YouStaying cool on hot days may be good advice for pregnant women and new moms concerned about their baby's later brain development..Sign up for our weekly HealthDay newsletter

Heatwaves During Pregnancy Could Affect Baby's Brain Development, Study Suggests

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