Reevaluating the Relationship Between Prenatal Employment and Birth Outcomes: A Policy-Relevant Application of Propensity Score Matching

Published:December 20, 2012DOI:



      Prior research shows an association between prenatal employment characteristics and adverse birth outcomes, but suffers methodological challenges in disentangling women's employment choices from birth outcomes, and little U.S.-based prior research compares outcomes for employed women with those not employed. This study assessed the effect of prenatal employment status on birth outcomes.


      With data from the Listening to Mothers II survey, conducted among a nationally representative sample of women who delivered a singleton baby in a U.S. hospital in 2005 (n = 1,573), we used propensity score matching to reduce potential selection bias. Primary outcomes were low birth weight (<2,500 g) and preterm birth (gestational age <37 weeks). Exposure was prenatal employment status (full time, part time, not employed). We conducted separate outcomes analyses for each matched cohort using multivariable regression models.


      Comparing full-time employees with women who were not employed, full-time employment was not causally associated with preterm birth (adjusted odds ratio [AOR], 1.37; p = .47) or low birth weight (AOR, 0.73; p = .41). Results were similar comparing full- and part-time workers. Consistent with prior research, Black women, regardless of employment status, had increased odds of low birth weight compared with White women (AOR, 5.07; p = .002).


      Prenatal employment does not independently contribute to preterm births or low birth weight after accounting for characteristics of women with different employment statuses. Efforts to improve birth outcomes should focus on the characteristics of pregnant women (employed or not) that render them vulnerable.
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      Katy B. Kozhimannil, PhD, MPA, is Assistant Professor in the Division of Health Policy and Management at the University of Minnesota. She is a health policy analyst who studies institutional and government policies affecting health care delivery, quality, and outcomes for women and families.


      Laura B. Attanasio, BA, is a doctoral student in the Division of Health Policy and Management, University of Minnesota. She applies sociological and health services research methods to questions of equity in maternal and reproductive health care.


      Patricia M. McGovern, PhD, MPH, is Professor in the Division of Environmental Health Sciences at the University of Minnesota. Her research applies the tools of health services research and policy to occupational and environmental health issues, in particular, issues of women's and children's health.


      Dwenda K. Gjerdingen, MD, MS, is a family physician and Professor at the University of Minnesota Medical School. She maintains an active clinical practice while also conducting research on women's mental and physical health, with a focus on pregnancy and the postpartum period.


      Pamela Jo Johnson, PhD, MPH, is a Research Investigator at Medica Research Institute and adjunct Assistant Professor in the Division of Epidemiology & Community Health at the University of Minnesota. She is a health services epidemiologist with broad interests in population health focusing on social disparities in health and healthcare.