The American Heart Association’s Hypertension journal published the study of pregnant women who breathed in high levels of fine particulate pollution - the hazy air seen over major urban areas around the world. They looked at 1,239 mothers and their children aged three to nine who live in the Boston, Massachusetts area.
As Reuters reported: “When they sorted children into three groups from highest to lowest levels of exposure...in the womb, children in the highest-exposure group were 61 per cent more likely to have high blood pressure than kids with the lowest exposure”.
The pollution of the areas where the women lived during their third trimesters were gauged by taking readings from Environmental Protection Agency (EPA) monitors nearby.
Children who were in the high-risk group were exposed to more than double the acceptable levels of fine particulate pollution set by the agency.
They were identified as having high blood pressure if their systolic - or the top number - blood pressure was in the highest 10 per cent for those their same age.
Study co-author Dr Noel Mueller, who works at Johns Hopkins University’s school of public health, said breathing in the pollution “causes an inflammatory response that alters genetic expression and fetal growth and development, on the pathway to high blood pressure in childhood”.
However, Mr Mueller cautioned that the study does not necessarily mean pregnant women or those looking to get pregnant should leave where they live now, just that they may want to avoid high pollution areas during their pregnancy.
He said this was important to remember especially during exercising, which he recommended for all expectant mothers, but just not in haze-filled areas.
Nearly 7.5m people around the world die each year from cardiovascular disease and high blood pressure is a major risk for it.
Dr Diane Gold, a professor at Harvard’s school of public health and who wrote an editorial about the study, told Reuters: "If maternal and early life pollution exposures increase the long-term risk of high blood pressure, then reducing early-life pollution exposure through regulation and through local and regional efforts may help protect children from having higher blood pressure in childhood, and may improve long-term cardiovascular and cerebrovascular health”.