title: Environmental tobacco smoke and risk of spontaneous abortion.
abstract: BACKGROUND
  Studies of exposure to environmental tobacco smoke (ETS) and risk of spontaneous abortion are limited to a few studies of self-reported exposure, and the results have been inconsistent. The aim of this study was to investigate risk of early spontaneous abortion related to ETS and active smoking as defined by plasma cotinine levels.
  
  
  METHODS
  We conducted a population-based case-control study in Uppsala County, Sweden, between January 1996 and December 1998. Cases were 463 women with spontaneous abortion at 6 to 12 completed weeks of gestation, and controls were 864 pregnant women matched to cases according to the week of gestation. Exposure status was defined by plasma cotinine concentrations: nonexposed, <0.1 ng/mL; ETS-exposed, 0.1-15 ng/mL; and exposed to active smoking, >15 ng/mL. Multivariable analysis was used to estimate the relative risk of spontaneous abortion associated with exposure to ETS and active smoking.
  
  
  RESULTS
  Nineteen percent of controls and 24% of cases were classified as having been exposed to ETS. Compared with nonexposed women, risk of spontaneous abortion was increased among both ETS-exposed women (adjusted odds ratio = 1.67; 95% confidence interval = 1.17-2.38) and active smokers (2.11; 1.36-3.27). We could not show a differential effect of exposure to ETS or active smoking between normal and abnormal fetal karyotype abortions.
  
  
  CONCLUSIONS
  Nonsmoking pregnant women exposed to ETS may be at increased risk of spontaneous abortion. Given the high prevalence of ETS exposure, the public health consequences of passive smoking regarding early fetal loss may be substantial.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, SE-171 77 Stockholm, Sweden. lena.george@ki.se
authors.forename: Lena
authors.initials: L
authors.lastname: George
authors.forename: Fredrik
authors.initials: F
authors.lastname: Granath
authors.forename: Anna L V
authors.initials: AL
authors.lastname: Johansson
authors.forename: Göran
authors.initials: G
authors.lastname: Annerén
authors.forename: Sven
authors.initials: S
authors.lastname: Cnattingius
mesh_terms: D000022:Abortion, Spontaneous / Q000139:chemically induced* / Q000453:epidemiology; D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D002110:Caffeine / Q000009:adverse effects; D016022:Case-Control Studies; D002869:Chromosome Aberrations; D003367:Cotinine / Q000097:blood* / Q000378:metabolism; D005260:Female; D005731:Ganglionic Stimulants / Q000009:adverse effects / Q000378:metabolism / Q000652:urine; D006801:Humans; D009325:Nausea / Q000150:complications; D009538:Nicotine / Q000009:adverse effects / Q000378:metabolism / Q000652:urine; D011247:Pregnancy; D013548:Sweden / Q000453:epidemiology; D014028:Tobacco Smoke Pollution / Q000009:adverse effects* / Q000032:analysis
chemical_list: D015415:Biomarkers; D005731:Ganglionic Stimulants; D014028:Tobacco Smoke Pollution; D002110:Caffeine; D009538:Nicotine; D003367:Cotinine