Exposure to high temperature and humidity during pregnancy may affect the future blood pressure of the unborn child, a new study has revealed.

In the study, published in the journal JACC: Advances, researchers found that prenatal exposure to higher humidity was associated with a faster increase in systolic and diastolic blood pressure, and a higher temperature was linked to a slower increase in systolic blood pressure in childhood.

Systolic blood pressure is the pressure in the arteries when the heart beats while diastolic blood pressure is the pressure when the heart rests between beats.

Children typically may have an increase in blood pressure from 3 to 10 years. However, the researchers noted that changes due to weather-related factors were linked to a different rate of increase.

"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," Dr. Ana Gonçalves Soares, lead researcher of the study, said in a news release.

Previous studies have assessed how urban environmental exposures such as air pollution during pregnancy could affect blood pressure in childhood. However, they were based on single exposure and blood pressure was measured only at a single point during childhood.

In the latest study, researchers used repeated measures of blood pressure to understand how exposure to high temperature and humidity affects changes in systolic and diastolic blood pressure from childhood to early adulthood.

"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," Dr. Soares said.

Over 7,000 participants between 3 and 24 years took part in the study. They were part of Bristol's Children of the 90s study, a longitudinal study that evaluated how various characteristics of the urban environment in pregnancy affect blood pressure from childhood to early adulthood.

The team repeated the analysis in four independent European cohorts of over 9,000 individuals in Finland, France and the Netherlands.

After evaluating 43 different factors such as noise, air pollution, built environment, natural spaces, traffic, meteorology, and unhealthy food environment, they concluded that outdoor temperature and humidity during pregnancy could influence changes in the blood pressure of the child.

"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," Dr . Soares said.

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