Background: Numerous studies have examined associations between air pollution and pregnancy outcomes, but most have been restricted to urban populations living near monitors.

Objectives: We examined the association between pregnancy outcomes and fine particulate matter in a large national study including urban and rural areas.

Methods: Analyses were based on approximately 3 million singleton live births in Canada between 1999 and 2008. Exposures to PM_2.5 (particles of median aerodynamic diameter ≤ 2.5 μm) were assigned by mapping the mother’s postal code to a monthly surface based on a national land use regression model that incorporated observations from fixed-site monitoring stations and satellite-derived estimates of PM_2.5. Generalized estimating equations were used to examine the association between PM_2.5 and preterm birth (gestational age < 37 weeks), term low birth weight (< 2,500 g), small for gestational age (SGA; < 10th percentile of birth weight for gestational age), and term birth weight, adjusting for individual covariates and neighborhood socioeconomic status (SES).

Results: In fully adjusted models, a 10-μg/m³ increase in PM_2.5 over the entire pregnancy was associated with SGA (odds ratio = 1.04; 95% CI 1.01, 1.07) and reduced term birth weight (–20.5 g; 95% CI –24.7, –16.4). Associations varied across subgroups based on maternal place of birth and period (1999–2003 vs. 2004–2008).

Conclusions: This study, based on approximately 3 million births across Canada and employing PM_2.5 estimates from a national spatiotemporal model, provides further evidence linking PM_2.5 and pregnancy outcomes.

Citation: Stieb DM, Chen L, Beckerman BS, Jerrett M, Crouse DL, Omariba DW, Peters PA, van Donkelaar A, Martin RV, Burnett RT, Gilbert NL, Tjepkema M, Liu S, Dugandzic RM. 2016. Associations of pregnancy outcomes and PM_2.5 in a National Canadian Study. Environ Health Perspect 124:243–249; http://dx.doi.org/10.1289/ehp.1408995

Address correspondence to D.M. Stieb, Population Studies Division, Health Canada, 445-757 West Hastings St.–Federal Tower, Vancouver, British Columbia, Canada, V6C 1A1. Telephone: (604) 666-3701. E-mail: dave.stieb@hc-sc.gc.ca

We thank M. Smith-Doiron for assistance in managing monitoring data and creating maps.

Funding was provided by Health Canada and, for some aspects of the work, by Centers for Disease Control and Prevention award 200-2010-37394, and by National Institute of Environmental Health Science grant 5R01ES019573-04.

The authors declare they have no actual or potential competing financial interests.

Received: 24 July 2014 Accepted: 17 June 2015 Advance Publication: 19 June 2015 Final Publication: 1 February 2016

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