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Fetus who were exposed to higher levels of air pollution during the third trimester of their mother’s pregnancy had a higher risk of elevated blood pressure in childhood, according to new research in the American Heart Association’s journal Hypertension.
Fine particulate matter of 2.5 microns or less (PM2.5) is a form of air pollution produced by motor vehicles and the burning of oil, coal and biomass, and has been shown to enter the circulatory system and negatively affect human health. Previous studies found, direct exposure to fine air pollution was associated with high blood pressure in both children and adults and is a major contributor to illness and premature death.
High blood pressure during childhood can leads to high blood pressure in adulthood and hypertension is the leading cause of cardiovascular disease. Researchers examined mothers and their children who were part of the large, ongoing Boston Birth Cohort study. Blood pressure was measured at each childhood physical examination at 3- to 9- years old.
A systolic blood pressure was considered elevated if it was in the highest 10 percent for children the same age on national data. Researchers also adjusted for other factors known to influence childhood blood pressure, such as birthweight and maternal smoking.
They discovered that children exposed to higher levels (the top third) of ambient fine-particulate pollution in the womb during the third trimester were 61 percent more likely to have elevated systolic blood pressure in childhood compared to those exposed to the lowest level (the bottom third).
Higher exposure to air pollution in the third trimester, when fetal weight gain is the most rapid, was already known to lower birthweight, but this study found the association with elevated blood pressure regardless of whether a child was of low, normal or high birthweight.
A woman’s fine-particulate matter exposure before pregnancy was not associated with blood pressure in her offspring, thus providing evidence of the significant impact of in-utero exposure. Not only does exposure increase the risk of illness and death in those directly exposed, but it may also cross the placental barrier in pregnancy and effect fetal growth and increase future risks for high blood pressure.
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