Good Practices for the Design, Analysis, and Interpretation of Observational Studies on Birth Spacing and Perinatal Health Outcomes

Jennifer A. Hutcheon, University of British Columbia, Department of Obstetrics and Gynaecology
Susan Moskosky, U.S. Health and Human Services, Office of Population Affairs
Cande V. Ananth, Columbia University, Irving College of Physicians and Surgeons
Olga Basso, Columbia University, Mailman School of Public Health
Peter A. Briss, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion
Cynthia D. Ferré, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion
Brittni N. Frederiksen, U.S. Health and Human Services, Office of Population Affairs
Sam Harper, McGill University, Biostatistics, and Occupational Health
Sonia Hernández-Díaz DrPH, Harvard University, Harvard T. H. Chan School of Public Health
Ashley H. Hirai, US Department of Health and Human Services, Health Resources and Services Administration, Maternal and Child Health Bureau
Russell S. Kirby, University of South Florida College of Public Health
Mark A. Klebanoff, The Ohio State University, The Research Institute at Nationwide Children's Hospital
Laura Lindberg, Guttmacher Institute
Sunni L. Mumford, National Institute of Child Health and Human Development, Division of Intramural Population Health Research
Heidi D. Nelson, Oregon Health and Science University, Department of Medical Informatics and Clinical Epidemiology
Robert W. Platt, McGill University, Biostatistics, and Occupational Health
Lauren M. Rossen, National Center for Health Statistics, Centers for Disease Control and Prevention
Alison M. Stuebe, University of North Carolina at Chapel Hill School of Medicine, Department of Obstetrics and Gynecology
Marie E. Thoma, University of Maryland at College Park, Department of Family Science
Catherine J. Vladutiu, US Department of Health and Human Services, Health Resources and Services Administration, Maternal and Child Health Bureau
Katherine A. Ahrens PhD, University of Southern Maine, Muskie School of Public ServiceFollow

Document Type

Article

Publication Date

10-12-2018

Publication Title

Paediatric and Perinatal Epidemiology

Abstract

Background

Meta‐analyses of observational studies have shown that women with a shorter interpregnancy interval (the time from delivery to start of a subsequent pregnancy) are more likely to experience adverse pregnancy outcomes, such as preterm delivery or small for gestational age birth, than women who space their births further apart. However, the studies used to inform these estimates have methodological shortcomings.

Methods

In this commentary, we summarise the discussions of an expert workgroup describing good practices for the design, analysis, and interpretation of observational studies of interpregnancy interval and adverse perinatal health outcomes.

Results

We argue that inferences drawn from research in this field will be improved by careful attention to elements such as: (a) refining the research question to clarify whether the goal is to estimate a causal effect vs describe patterns of association; (b) using directed acyclic graphs to represent potential causal networks and guide the analytic plan of studies seeking to estimate causal effects; (c) assessing how miscarriages and pregnancy terminations may have influenced interpregnancy interval classifications; (d) specifying how key factors such as previous pregnancy loss, pregnancy intention, and maternal socio‐economic position will be considered; and (e) examining if the association between interpregnancy interval and perinatal outcome differs by factors such as maternal age.

Conclusion

This commentary outlines the discussions of this recent expert workgroup, and describes several suggested principles for study design and analysis that could mitigate many potential sources of bias.

Comments

This manuscript was supported, in part, by a contract between the Office of Population Affairs and Atlas Research, LLC [# HHSP233201450040A]. JAH is the recipient of New Investigator Awards from the Canadian Institutes of Health Research and the Michael Smith Foundation for Health Research. SLM was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health.

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