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Craig A. Hansen,¹ Adrian G. Barnett,² and Gary Pritchard³

¹School of Medicine, and ²School of Population Health, University of Queensland, Queensland, Australia; ³PacUser, Paddington, Queensland, Australia

Abstract
Background: Over the past decade there has been mounting evidence that ambient air pollution during pregnancy influences fetal growth.

Objectives: This study was designed to examine possible associations between fetal ultrasonic measurements collected from 15,623 scans (13–26 weeks gestation) and ambient air pollution during early pregnancy.

Methods: We calculated mothers' average monthly exposures over the first 4 months of pregnancy for the following pollutants: particulate matter < 10 µm aerodynamic diameter (PM₁₀) , ozone, nitrogen dioxide, and sulfur dioxide. We examined associations with fetal femur length (FL) , biparietal diameter (BPD) , head circumference (HC) , and abdominal circumference (AC) . Final analyses included scans from only those women within 2 km of an air pollution monitoring site. We controlled for long-term trend, season, temperature, gestation, mother's age, socioeconomic status, and fetal sex.

Results: A reduction in fetal AC was associated with O₃ during days 31–60 [–1.42 mm ; 95% confidence interval (CI) , –2.74 to –0.09], SO₂ during days 61–90 (–1.67 mm ; 95% CI, –2.94 to –0.40) , and PM₁₀ during days 91–120 (–0.78 mm ; 95% CI, –1.49 to –0.08) . Other results showed a reduction in BPD (–0.68 mm ; 95% CI, –1.09 to –0.27) associated with SO₂ during days 0–30, a reduction in HC (–1.02 mm ; 95% CI, –1.78 to –0.26) associated with PM₁₀ during days 91–120, and a reduction in FL associated with PM₁₀ during days 0–30 (–0.28 mm ; 95% CI, –0.48 to –0.08) and 91–120 (–0.23 ; 95% CI, –0.42 to –0.04) .

Conclusion: We found strong effects of ambient air pollution on ultrasound measures. Future research, including more individually detailed data, is needed to confirm our results.

Key words: air pollution, fetal growth, pregnancy, temperature, ultrasound. Environ Health Perspect 116: 362–369 (2008) . doi:10.1289/ehp.10720 available via http://dx.doi.org/ [Online 17 December 2007]

Address correspondence to C. Hansen, National Center for Environmental Assessment, U.S. Environmental Protection Agency, Mail Drop B243-01, Research Triangle Park, NC 27711, USA. Telephone: (919) 541-0673. Fax: (919) 541-2985. Email: Hansen.Craig@epamail.epa.gov

We thank D. Neale from Queensland Environmental Protection Agency for the air pollution data, and the Bureau of Meteorology for the temperature and sunlight data recorded at the Brisbane airport.

The authors declare they have no competing financial interests.

Received 30 July 2007 ; accepted 17 December 2007.