Babies born following 2003 wildfires have lower birthweight, study shows

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Babies born to women pregnant during wildfires in Southern California in 2003 tended to have slightly lower birthweights than babies born to women pregnant in the same area at other times, according to a recently released study out of UC Berkeley.

The study, published in the September 2012 issue of the journal Environmental Health Perspectives, examined data on births of babies born to women living in the South Coast Air Basin who were pregnant during this period as well as data for babies from the same area born before and after October 2003. The South Coast Air Basin includes Orange County as well as parts of Los Angeles, San Bernardino and Riverside counties. Smoke from a series of wildfires that destroyed more than 750,000 acres of forest blanketed the area in late October 2003, according to the study.

Rachel Morello-Frosch, one of the study’s authors and a campus associate professor in the department of environmental science, policy and management, said the study was prompted in part by the increasing frequency of wildfires in western regions, including California.

The researchers studied a total of more than 138,000 birth records of pregnant women in all three trimesters who were exposed to smoke from the fires in Southern California, according to the study.

The study found a slight reduction, ranging between three to 10 grams, in the birthweight of babies born to women who lived in the area during the fires.

“In the delivery room, a reduction of seven to 10 grams isn’t a big deal,” Morello-Frosch said. “But decrements in birthweight in a large population might mean shifting the birthweight profile of a large population downward. Combined with other pollutants that also reduce birthweight, this is significant.”

The level of reduction may not be very clinically significant but could be statistically relevant, said T. Allen Merritt, a professor of pediatrics at Loma Linda University School of Medicine.

Carrie Breton, an assistant professor of preventive medicine at the USC Keck School of Medicine, is studying the effects of the same set of fires to determine the effect of individuals’ varying levels of exposure to particulate matter on birthweight. Breton said her research has shown similar results.

“The trends are the same — it’s very comforting, in terms of confirming the connection between wildfires and small but significant effects on birthweights,” she said.

It is not clear what differentiates wildfire smoke from other kinds of smoke and air pollution in their effects on birthweights, but said the size of the particles and components of the smoke could be significant, said Bill Jesdale, a co-author of the UC Berkeley study.

The ecological effects of climate change may make the probability of wildfires higher as dry seasons increase in length.

“We are projected to have drier and hotter times ahead in California,” Jesdale said.

Contact Gautham Thomas at [email protected]