Outdoor humidity, temperature during pregnancy found to affect child's blood pressure

New Delhi: Exposure to outdoor humidity and temperature levels during pregnancy are associated with blood pressure changes in children, a new study has found.

An international team of researchers found that exposure to higher relative humidity while pregnant was linked to a steeper increase in blood pressure in childhood, whereas being exposed to higher temperatures during pregnancy was linked to a slower increase in blood pressure in childhood (age 3-10 years).

The researchers, including those from the University of Bristol, UK, said that while it is normal for blood pressure to rise as children grow, the study showed a slightly bigger increase.

Their findings suggested that humidity and temperature during pregnancy could change the child's blood pressure, they said.

"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 Ana Gonçalves Soares from the University of Bristol, and lead author of the study published in the Journal of the American College of Cardiology (JACC): Advances.

For the study, the researchers analysed blood pressure measurements in over 7,000 participants aged between 3 and 24 years to assess the relationship between exposure to various urban environmental characteristics during pregnancy, like temperature and pollution, and blood pressure from childhood to early adulthood.

They repeated the analyses in four other European groups from Finland, France and the Netherlands, which collectively included over 9,000 participants.

Previous studies have shown certain urban environmental exposures during pregnancy to be linked with changes in 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," said Gonçalves Soares.

While the mechanisms underlying the link between ambient environmental conditions and blood pressure are not fully understood, the researchers suggested that "lower ambient temperature activates the sympathetic nervous system and increases vasoconstriction (or narrowing of blood vessels) leading to increase in heart rate and blood pressure." However, the mechanisms through which outdoor temperature (and humidity) during pregnancy might influence offspring blood pressure require further investigation, they said.

"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," said Gonçalves Soares.