title: Ambient air pollution and adverse birth outcomes: Differences by maternal comorbidities.
abstract: Prenatal exposure to ambient air pollution has been associated with adverse birth outcomes, but the potential modifying effect of maternal comorbidities remains understudied. Our objective was to investigate whether associations between prenatal air pollution exposures and birth outcomes differ by maternal comorbidities.
  
  
  
  A total of 818,400 singleton live births were identified in the province of Ontario, Canada from 2005 to 2012. We assigned exposures to fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ozone (O3) to maternal residences during pregnancy. We evaluated potential effect modification by maternal comorbidities (i.e. asthma, hypertension, pre-existing diabetes mellitus, heart disease, gestational diabetes and preeclampsia) on the associations between prenatal air pollution and preterm birth, term low birth weight and small for gestational age.
  
  
  
  Interquartile range (IQR) increases in PM2.5 (2μg/m(3)), NO2 (9ppb) and O3 (5ppb) over the entire pregnancy were associated with a 4% (95% CI: 2.4-5.6%), 8.4% (95% CI: 5.5-10.3%) and 2% (95% CI: 0.5-4.1%) increase in the odds of preterm birth, respectively. Increases of 10.6% (95% CI: 0.2-2.1%) and 23.8% (95% CI: 5.5-44.8%) in the odds of preterm birth were observed among women with pre-existing diabetes while the increases were of 3.8% (95% CI: 2.2-5.4%) and 6.5% (95% CI: 3.7-8.4%) among women without this condition for pregnancy exposure to PM2.5 and NO2, respectively (Pint<0.01). The increase in the odds of preterm birth for exposure to PM2.5 during pregnancy was higher among women with preeclampsia (8.3%, 95% CI: 0.8-16.4%) than among women without (3.6%, 95% CI: 1.8-5.3%) (Pint=0.04). A stronger increase in the odds of preterm birth was found for exposure to O3 during pregnancy among asthmatic women (12.0%, 95% CI: 3.5-21.1%) compared to non-asthmatic women (2.0%, 95% CI: 0.1-3.5%) (Pint<0.01). We did not find statistically significant effect modification for the other outcomes investigated.
  
  
  
  Findings of this study suggest that associations of ambient air pollution with preterm birth are stronger among women with pre-existing diabetes, asthma, and preeclampsia.
authors.affiliation: Air Health Science Division, Health Canada, Ottawa, Ontario, Canada; School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa, Ontario, Canada. Electronic address: eric.lavigne@hc-sc.gc.ca.
authors.forename: Eric
authors.initials: E
authors.lastname: Lavigne
authors.affiliation: Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Better Outcomes Registry and Network Ontario, Ottawa, Ontario, Canada; Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada.
authors.forename: Abdool S
authors.initials: AS
authors.lastname: Yasseen
authors.affiliation: Population Studies Division, Health Canada, Vancouver, British Columbia, Canada.
authors.forename: David M
authors.initials: DM
authors.lastname: Stieb
authors.affiliation: College of Public Health and Human Sciences, Oregon State University, Corvallis, OR, USA.
authors.forename: Perry
authors.initials: P
authors.lastname: Hystad
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Aaron
authors.initials: A
authors.lastname: van Donkelaar
authors.affiliation: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: Randall V
authors.initials: RV
authors.lastname: Martin
authors.affiliation: Air Quality Research Division, Environment Canada, Downsview, Ontario, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Brook
authors.affiliation: Department of Sociology, University of New Brunswick, Fredericton, New Brunswick, Canada.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Crouse
authors.affiliation: Population Studies Division, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Burnett
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada; Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Quebec, Canada.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.affiliation: Air Health Science Division, Health Canada, Ottawa, Ontario, Canada; Institute of Health: Science, Technology and Policy, Carleton University, Ottawa, Ontario, Canada.
authors.forename: Scott
authors.initials: S
authors.lastname: Weichenthal
authors.affiliation: Air Health Science Division, Health Canada, Ottawa, Ontario, Canada.
authors.forename: Markey
authors.initials: M
authors.lastname: Johnson
authors.affiliation: Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Villeneuve
authors.affiliation: Ottawa Hospital Research Institute, Ottawa, Ontario, Canada; Better Outcomes Registry and Network Ontario, Ottawa, Ontario, Canada; Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada; Public Health Ontario, Toronto, Ontario, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Walker
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis; D001249:Asthma / Q000453:epidemiology*; D015897:Comorbidity; D003920:Diabetes Mellitus / Q000453:epidemiology*; D005260:Female; D006331:Heart Diseases / Q000453:epidemiology; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D007231:Infant, Newborn; D008297:Male; D018811:Maternal Exposure; D009585:Nitrogen Dioxide / Q000032:analysis; D009864:Ontario; D010126:Ozone / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D011225:Pre-Eclampsia / Q000453:epidemiology*; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone; D009585:Nitrogen Dioxide
keywords: Air pollution; Birth outcome; Comorbidity; Maternal; Prenatal