Humidity and temperature affect foetuses' future blood pressure

Outdoor humidity and temperature levels during pregnancy appear to affect the future blood pressure of the unborn child, according to an international study led by the University of Bristol. Although an increase in blood pressure is normal during childhood, these weather-related factors were associated with a different rate of increase.

Previous studies have mostly measured blood pressure at a single time point, predominantly focusing on single exposures, particularly air pollution. In this latest study, which was part of the LongITools project, researchers used repeated measures of blood pressure to assess the association of a range of prenatal urban environmental exposures with changes in systolic and diastolic blood pressure from childhood to early adulthood.

The study analysed repeated blood pressure measurements in over 7000 participants aged between three and 24 years from Bristol’s Children of the 90s study. Analyses were repeated in four independent European cohorts in over 9000 individuals in Finland, France and the Netherlands. The research team explored 43 different measures of noise, air pollution, built environment, natural spaces, traffic, meteorology and unhealthy food environment, and found that prenatal outdoor temperature and humidity could influence changes in blood pressure, especially in childhood.

Their results, published in JACC: Advances, showed that higher humidity was associated with a faster increase and higher temperature with a slower increase in systolic blood pressure in childhood. Higher humidity was also associated with a faster increase in diastolic blood pressure in childhood. In the UK cohort, higher levels of air pollution were associated with a faster increase in diastolic blood pressure in childhood and a slower increase in adolescence, but this association was not replicated in other cohorts. There was little evidence of an association of other urban environmental exposures with changes in systolic or diastolic blood pressure.

“Children with higher blood pressure are more likely to have higher blood pressure as adults, which can increase the risk of heart disease and stroke as well as kidney disease and vascular dementia,” said Dr Ana Gonçalves Soares, lead researcher on the study.

“Previous studies have already shown that some urban environmental exposures during pregnancy are associated with blood pressure in childhood. We were able to expand that further and explore whether these environmental exposures are also associated with trajectories (changes) of blood pressure from childhood to early adulthood.

“The findings suggest that humidity and temperature during pregnancy could change the child’s blood pressure. Further work is needed to be carried out to understand how weather-related conditions during pregnancy can affect the child’s blood pressure to inform strategies to prevent cardiovascular disease in later adulthood related to prenatal environmental exposures.”

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