Thanks to a temporary reduction of air pollution, women in Beijing who were pregnant during the 2008 Olympics gave birth to babies who weighed more. According to findings published in Environmental Health Perspectives this week, exposure to high levels of pollution during the final weeks of a pregnancy can significantly impact the growth and development of the fetus.
Previous work have linked low birth weight with high concentrations of air pollutants experienced during pregnancy -- but when during the pregnancy does pollution make the biggest difference? To figure this out, a team led by University of Rochester’s David Rich and Kaibo Liu of Capital Medical University in Beijing turned to a natural experiment: In the months leading up to the 2008 Olympics and Paralympics, the Chinese government launched a series of measures to improve the capital city’s notoriously bad air quality. Restrictions were placed on auto use, factories were closed, construction projects were stopped, and there were also attempts at cloud seeding. The result was a six-to-seven-week period that boasted a 60 percent reduction in sulfur dioxide concentrations, a 48 percent reduction in carbon monoxide, a 43 percent reduction in nitrogen dioxide, and fewer particles that were smaller than 2.5 microns in diameter.
The team looked at data on 83,672 full-term births by women living in four urban districts of Beijing, taking note of how many months pregnant each mother-to-be was from August 8 through September 24, 2008. Then they compared the birth weights of these Olympic babies to newborns from the same period in 2007 and 2009.
Women who were pregnant during the games gave birth to children with higher birth weights, compared to those who were pregnant before and after the games. In particular, women who were eight months pregnant during the Olympics gave birth to babies who were, on average, 23 grams heavier. The team saw no major link between pollution and birth weight for months one through seven.
“The results of this study demonstrate a clear association between changes in air pollutant concentrations and birth weight,” Rich says in a news release. Late in the pregnancy, the fetus experiences the most amount of physical growth, and the development of the central nervous, cardiovascular, and musculoskeletal systems really accelerates. “These findings not only illustrate one of the many significant health consequences of pollution,” Rich adds, “but also demonstrate that this phenomenon can be reversed.” Though, researchers have yet to figure out exactly how pollution causes lower birth weights. [Via University of Rochester]