Birth-weight boost tied to cleaner air during Beijing Olympics

young child in polluted Beijing

Beijing, known for its pollution, took measures to improve air quality during the 2008 Summer Olympics and Paralympics. Babies born shortly after the games were slightly heavier than babies born a year earlier or later, a new study finds. 


The Olympics are stuffed full of feel-good moments featuring amazing athletic feats, heart-warming backstories and national pride. Now, a new study details another Olympic win: Bigger babies.

Babies whose eighth month of gestation fell during the 2008 Beijing Olympics and Paralympics were born slightly heavier than babies born a year earlier or later. Why? Because those Olympic babies got a break from Beijing’s profoundly polluted air, researchers suggest April 28 in Environmental Health Perspectives. The results serve as a stark reminder of how pollution can harm fetuses.

Olympic organizers in Beijing went to great lengths to clean up their air in advance of the 2008 Summer Games. The government took cars off roads, shuttered factories and even banned outdoor spray-painting. And those efforts worked. Concentrations of certain pollutants dropped.

Researchers led by epidemiologist David Rich of the University of Rochester Medical Center in New York realized that this rare break in pollution was a golden opportunity to study the effects of dirty air on pregnancy.

The team combed through health records of more than 80,000 pregnant women in Beijing to see whether the pollution drop had any effect on the outcome. Women whose eighth month of pregnancy coincided with the Olympics went on to have babies who were an average of 23 grams heavier than the babies of women whose eighth month of pregnancy came the year before or after, the researchers found.

That average birth weight may have responded to such a short bout of clean air makes you wonder what pollution is doing to fetuses who experience it for all 40 weeks. “Even in this 47-day period you see a public health benefit like this,” Rich says. “Imagine what you could do if you could have air pollution levels reduced throughout the whole entire pregnancy.”

The timing of the pregnancy seemed to matter. The researchers found that baby weight went up when clearer skies coincided with the eighth month of pregnancy, a time when a fetus is really packing on pounds. Finding an effect there “makes a lot of sense,” says epidemiologist Beate Ritz of the University of California, Los Angeles, who wasn’t involved in the study.

Twenty-three grams — about 0.8 ounces — isn’t a big difference. In fact, it’s less than 1 percent of these babies’ median weight. But that slight change may serve as a bellwether for more insidious effects.

“It’s really important, not so much as ‘Oh, those few grams, do they really matter in the life of this child?’’ Ritz says. “That’s not really what we’re asking.” Instead, scientists suspect that if pollution is behind the weight difference, then dirty skies could be inflicting damage on other developing organs and systems too. Pollution during pregnancy could be programming these babies to develop in a way that leads to important differences in the immune system, the brain and other systems, she says.

It’s also possible that pollution might do more damage earlier in pregnancy, Ritz says. Dirty air could be contributing to early miscarriages, which would be hard to study.

More research is needed to figure out just how the pollution may be affecting fetuses, and babies, and people for that matter. But what people really need is more than just a temporary reprieve from pollution.

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Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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