title: Factors associated with employment status before and during pregnancy: Implications for studies of pregnancy outcomes.
abstract: Potential confounding or effect modification by employment status is frequently overlooked in pregnancy outcome studies.
  
  
  
  To characterize how employed and non-employed women differ, we compared demographics, behaviors, and reproductive histories by maternal employment status for 8,343 mothers of control (non-malformed) infants in the National Birth Defects Prevention Study (1997-2007) and developed a multivariable model for employment status anytime during pregnancy and the 3 months before conception.
  
  
  
  Sixteen factors were independently associated with employment before or during pregnancy, including: maternal age, pre-pregnancy body mass index, pregnancy intention, periconceptional/first trimester smoking and alcohol consumption, and household income.
  
  
  
  Employment status was significantly associated with many common risk factors for adverse pregnancy outcomes. Pregnancy outcome studies should consider adjustment or stratification by employment status. In studies of occupational exposures, these differences may cause uncontrollable confounding if non-employed women are treated as unexposed instead of excluded from analysis. Am. J. Ind. Med. 60:329-341, 2017. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio.
authors.forename: Carissa M
authors.identifier: 0000-0001-5804-1874
authors.initials: CM
authors.lastname: Rocheleau
authors.affiliation: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Bertke
authors.affiliation: Division of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio.
authors.forename: Christina C
authors.initials: CC
authors.lastname: Lawson
authors.affiliation: Department of Epidemiology, College of Public Health, The University of Iowa, Iowa City, Iowa.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Romitti
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Tania A
authors.initials: TA
authors.lastname: Desrosiers
authors.affiliation: Division of Epidemiology, Human Genetics and Environmental Sciences, School of Public Health, University of Texas at Houston, Houston, Texas.
authors.forename: A J
authors.identifier: 0000-0002-5874-4155
authors.initials: AJ
authors.lastname: Agopian
authors.affiliation: Department of Environmental Health Sciences, School of Public Health, The University at Albany-SUNY, Rensselaer, North Carolina.
authors.forename: Erin
authors.initials: E
authors.lastname: Bell
authors.affiliation: Division of Congenital and Developmental Disorders, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Gilboa
mesh_terms: D000328:Adult; D015992:Body Mass Index; D004651:Employment / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007182:Income; D008423:Maternal Age; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology*; D016273:Occupational Exposure / Q000009:adverse effects; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology / Q000209:etiology*; D011256:Pregnancy Outcome; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: confounding factors (epidemiology); employment; healthy worker effect; pregnancy