Pregnant women who live in neighbourhoods with lots of air
pollution may be slightly more likely to develop high blood pressure, a new
Past research suggests people with high blood pressure have
often been exposed to more air pollution in the past than those with normal
blood pressure. But few studies have looked to see whether that's the case for
Women develop high blood pressure during about one in ten
pregnancies. Having so-called gestational hypertension makes it more likely
that a woman will need a caesarean section, that she will give birth early and
that her baby will be born small. "Our results suggest air pollution does
have some impact on the risk of gestational hypertension," said epidemiologist
Dr Xiaohui Xu.
He led the study at the University of Florida in
Gainesville."This could have some subsequent effects on both maternal and
foetal health," Xu told Reuters Health. However, he said, "This was a
pilot study, meaning it was meant to test for any potential impact of pollution
on blood pressure." Researchers said the results still leave many
Xu and his colleagues used data on about 22 000 women who
gave birth in Jacksonville, Florida, in 2004 and 2005. Birth records showed
just over 1 000 women, close to 5%, developed high blood pressure during
More research needed
The researchers linked each woman's home address to data
from the nearest US Environmental Protection Agency air quality monitor.
Monitors record how much nitrogen dioxide, carbon monoxide and other pollutants
are in the air each day.
Women who lived near monitors that recorded high levels of
four pollutants, including nitrogen dioxide and fine particle pollution, throughout
pregnancy had 12% to 24% higher odds of getting hypertension than women with
The patterns were similar when the researchers looked only
at exposure to air pollution during the first trimester or second trimester,
they reported in the Journal of Epidemiology and Community Health. "The
study is provocative without being definitive in any way," said Dr Jodi
Abbott, an associate professor of maternal-foetal medicine at the Boston
University School of Medicine.
Abbott, who was not involved in the research, said it had
some key limitations. For example, some factors that affect a woman's risk of
getting high blood pressure, such as her weight, were not taken into account.
In addition, the study did not look at whether any women moved to a different
neighbourhood while pregnant or spent most of their time away from home, where
pollution was measured.
For those reasons, Abbott told Reuters Health, more research
is needed to determine whether there are any blood pressure-related benefits to
moving to an area with less pollution, or to staying indoors on high-pollution
days while pregnant. "I would not make any recommendations to my patients
based on this research," she said. The author is a student at the Boston
University School of Medicine, and Abbott is a former professor of hers.