Air pollution increases hypertension risk in pregnant women

A new study has found that breathing in harmful toxics during pregnancy increases risk of hypertension in women and may result in deadly complications like preeclampsia.

Researchers at the University of Florida compared birth data with Environmental Protection Agency estimates of air pollution, finding that heavy exposure to four air pollutants led to a significantly increased risk for developing a high blood pressure disorder during pregnancy.

The pollutants include two specific types of fine and coarse particulate matter, carbon monoxide and sulfur dioxide. According to the EPA, particulate matter includes acids, dust, metals and soil particles.

These inhalable particles are released from industries and forest fires and can form when gases react with each other in the air. Sulfur dioxide is emitted from power plants and industries. Most carbon monoxide is produced by car exhaust.

Xiaohui Xu, an assistant professor of epidemiology in the colleges of Public Health and Health Professions and Medicine, said that fetal development is very sensitive to environmental factors and hypertension (high BP), in particular, is associated with increased morbidity and mortality, causing a lot of problems for the mother and fetus, including preterm delivery.

To gain a better understanding of how environmental factors may play a role in increasing the risk of developing hypertension during pregnancy, the researchers examined data from women who gave birth in Jacksonville, Fla., between 2004 and 2005 and environmental data from their communities. The sample included more than 22,000 pregnant women.

The researchers did not include mothers with chronic hypertension, those who had previously given birth prematurely or those whose babies were born with other complications in the sample.

They then gauged how much pollution the women were exposed to throughout their pregnancies using data the EPA gathered daily to measure the levels of several pollutants.

Among the sample of women, 4.7 percent developed a hypertensive disorder during pregnancy. Exposure to air pollutants throughout the first two trimesters of pregnancy increased women's risk of developing one of these conditions, Xu said.

They determined this after controlling for other factors that could affect a woman's risk for developing hypertension, such as socioeconomic status, exposure to co-pollutants and smoking during pregnancy.

But they could not determine conclusively whether exposure early in the pregnancy or late in the pregnancy was more likely to increase a woman's risk for hypertension.

"It looks like the whole period has impacts for hypertension," he said.

On the basis of these findings, the researchers say more air pollution control is necessary to prevent dangerous complications in pregnant women and babies.

The study is published in the Journal of Epidemiology and Community Health.