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In a new study, Chinese mothers with exposure to a high level of certain kinds of air pollution during pregnancy had a higher risk of abnormal fetal growth.

The findings, which appear in the International Journal of Epidemiology, are based on data from more than 8,000 women in Lanzhou, China from 2010 to 2012.

The researchers say that, to their knowledge, it is the first study of its kind to take place in areas with very high air pollution levels.

“There is a lack of studies investigating the association between air pollution and fetal overgrowth,” says Yawei Zhang, associate professor at the Yale University School of Public Health. “We analyzed data from Lanzhou Birth Cohort Study to investigate the hypothesis that exposure to high levels of PM10 during pregnancy increases the risk of abnormal fetal growth, including both undergrowth and overgrowth, to determine if and how expectant mothers could protect themselves from possible contributing pollutants.”

In collaboration with researchers from the Gansu Provincial Maternity and Child Care Hospital, the Yale scientists collected the daily average concentration for PM10—a diverse class of air pollution with health implications—from the government monitoring stations in Lanzhou. Using ultrasound measures of four fetal growth parameters during pregnancy, the researchers examined the associations between PM10 exposure and risk of abnormal fetal growth.

The researchers consistently identified positive associations between higher levels of exposure to a mixture of pollutants from car fumes, industry emissions, or construction activities and fetal head circumference overgrowth, they say.

They collected pregnant women’s home and work addresses through in-person interviews, and calculated daily PM10 concentrations by incorporating each participant’s home and work addresses.

Zhang says other studies in different populations should confirm the finding that high levels of PM10 are associated with risk of overgrowth, and that it is also important to identify the specific pollutants that are responsible for this association by investigating the components of PM10.

“Our results have important public health implications and call for future studies to explore the underlying mechanisms and postnatal consequences to the findings,” says Zhang. “We are going to replicate the findings in another birth cohort and will continue to identify individuals who are more susceptible to air pollution.”

Women in the region may lower the risk of fetal overgrowth by choosing their inception time and reducing their outdoor activities during the days with high air pollution, says Zhang.

Pregnant women who came to the Gansu Provincial Maternity and Child Care Hospital for delivery in 2010-2012 and who were 18 years or older with gestation age of more than 20 weeks were eligible to participate in this study.

Funding for the work came from Gansu Provincial Maternity and Child Care Hospital, Gansu Provincial Science and Technology Department, the National Institutes of Health, and the US Environmental Protection Agency.

Source: Rosalind D’Eugenio for Yale University