title: Ozone and hypertensive disorders of pregnancy in Florida: Identifying critical windows of exposure.
abstract: BACKGROUND
  Ozone (O3) has been linked to hypertensive disorders of pregnancy (HDP). However, inconsistent results have been reported, and no study has examined the critical exposure windows during pregnancy.
  
  
  METHODS
  We used Florida birth vital statistics records to investigate the association between HDP and O3exposure among 655,529 pregnancies with conception dates between 2005 and 2007. Individual O3exposure was assessed at mothers' home address at the time of delivery using the Hierarchical Bayesian space-time statistical model. We examined the association during three predefined exposure windows including trimester 1, trimester 2, and trimesters 1&2, as well as in each week of the first two trimesters using distributed lag models.
  
  
  RESULTS
  Pregnancies with HDP had a higher mean exposure to O3(39.07 in trimester 1, 39.02 in trimester 2, and 39.06 in trimesters 1&2, unit: ppb) than those without HDP (38.65 in trimester 1, 38.57 in trimester 2, and 38.61 in trimesters 1&2, unit: ppb). In the adjusted logistic regression model, increased odds of HDP were observed for each 5 ppb increase in O3(ORTrimester1=1.04, 95% CI: 1.03, 1.06; ORTrimester2=1.03, 95% CI: 1.02, 1.04; ORTrimester1&2=1.07, 95% CI: 1.05, 1.08). In the distributed lag models, elevated odds of HDP were observed with increased O3exposure during the 1st to 24th weeks of gestation, with higher odds during early pregnancy.
  
  
  CONCLUSIONS
  O3exposure during pregnancy is related to increased odds of HDP, and early pregnancy appears to be a potentially critical window of exposure.
authors.affiliation: Department of Epidemiology, College of Public Health and Health Professions and College of Medicine, University of Florida, Gainesville, FL, USA. Electronic address: huihu@ufl.edu.
authors.forename: Hui
authors.initials: H
authors.lastname: Hu
authors.affiliation: Epidemiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, 20892 USA.
authors.forename: Sandie
authors.initials: S
authors.lastname: Ha
authors.affiliation: Department of Epidemiology & Biostatistics, School of Public Health, Texas A&M University, College Station, TX, USA. Electronic address: xiaohui.xu@sph.tamhsc.edu.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Xu
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D005431:Florida / Q000453:epidemiology; D006801:Humans; D006973:Hypertension / Q000139:chemically induced* / Q000453:epidemiology; D018811:Maternal Exposure; D010126:Ozone / Q000009:adverse effects*; D011225:Pre-Eclampsia / Q000453:epidemiology; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000139:chemically induced* / Q000453:epidemiology; D011261:Pregnancy Trimester, First; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D010126:Ozone
keywords: Air pollution; Hypertensive disorders of pregnancy; Ozone; Windows of exposure