Hot or humid days during pregnancy could influence the future heart health of your unborn child, a new study finds.

The children of expecting moms exposed to high humidity tended to have a steeper increase in blood pressure through ages 3 to 10, researchers reported Jan. 8 in the journal JACC: Advances .

On the other hand, exposure to higher temperatures in the womb was associated with a slower increase in blood pressure.

Increases in blood pressure are normal as children age, but these weather-related factors appeared to alter the rate of increase, the researchers 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 lead researcher Dr. Ana Gonçalves Soares , a research fellow in epidemiology with the University of Bristol Medical School in the U.K.

“The findings suggest that humidity and temperature during pregnancy could change the child’s blood pressure,” Soares said.

For the study, researchers took repeated blood pressure measurements of more than 7,000 participants ages 3 to 24, all of whom were enrolled in a long-term study of children born in the 1990s.

Similar measurements also were repeated in more than 9,000 participants in Finland, France and the Netherlands.

The research team explored 43 different factors that could influence the health of unborn children, including noise, air pollution, traffic, weather, natural spaces and diet.

They found that that higher humidity was associated with a faster increase in both systolic and diastolic blood pressure during childhood.

At the same time, high temperatures were associated with a slower increase in systolic blood pressure, results show.

The U.K. kids also experienced a faster increase in diastolic blood pressure during childhood if they were exposed to high levels of air pollution in the womb. However, air pollution exposure also produced a slower increase in blood pressure during their teen years.

The researchers found little evidence of other environmental exposures altering kids’ blood pressure as they grew.

“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 exposure,” Soares concluded.

More information

The American College of Nurse-Midwives have more about environmental exposures during pregnancy .

SOURCE: University of Bristol, news release, Jan. 10, 2024