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Original Investigation
July 26, 2016

Temporal Trends in Late Preterm and Early Term Birth Rates in 6 High-Income Countries in North America and Europe and Association With Clinician-Initiated Obstetric Interventions

Author Affiliations
  • 1Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia
  • 2Departments of Pediatrics and of Epidemiology, Biostatistics and Occupational Health, McGill University Faculty of Medicine, Montreal, Quebec, Canada
  • 3Centre for Chronic Disease Prevention, Surveillance and Epidemiology Division, Public Health Agency of Canada, Ottawa, Ontario, Canada
  • 4Section of Social Medicine, University of Copenhagen, and Methods and Analysis, Statistics, Denmark, Copenhagen, Denmark
  • 5Information Services Department, National Institute for Health and Welfare, Helsinki, Finland
  • 6Departments of Global Public Health and Primary Care and Clinical Sciences, University of Bergen, Norway
  • 7Department of Obstetrics and Gynecology, Haukeland University Hospital, Bergen, Norway
  • 8Department of Global Public Health and Primary Care, University of Bergen, Norway
  • 9Clinical Epidemiology Unit, T2, Department of Medicine Solna, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden
  • 10INSERM UMR 1153, Center for Epidemiology and Statistics Sorbonne Paris Cité, Paris Descartes University, Paris, France
  • 11Department of Obstetrics and Gynecology and Women’s Health, Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, New York
  • 12Department of Social Medicine, National Center for Child Health and Development, Tokyo, Japan
  • 13Departments of Pediatrics and Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
JAMA. 2016;316(4):410-419. doi:10.1001/jama.2016.9635
Key Points

Question  Are temporal trends in late preterm and early term birth rates in 6 high-income countries associated with use of clinician-initiated obstetric interventions?

Findings  These population-based retrospective analyses of singleton live births found declining late preterm birth rates in Norway and the United States and declining early term birth rates in Norway, Sweden, and the United States. Obstetric interventions increased in some countries but decreased in the United States, where an association was observed with decreasing early term birth rates.

Meaning  Decreasing US early term birth rates were associated with decreasing rates of clinician-initiated obstetric interventions; obstetric interventions increased in some other countries but with no association with late preterm or early term birth rates.

Abstract

Importance  Clinicians have been urged to delay the use of obstetric interventions (eg, labor induction, cesarean delivery) until 39 weeks or later in the absence of maternal or fetal indications for intervention.

Objective  To describe recent trends in late preterm and early term birth rates in 6 high-income countries and assess association with use of clinician-initiated obstetric interventions.

Design  Retrospective analysis of singleton live births from 2006 to the latest available year (ranging from 2010 to 2015) in Canada, Denmark, Finland, Norway, Sweden, and the United States.

Exposures  Use of clinician-initiated obstetric intervention (either labor induction or prelabor cesarean delivery) during delivery.

Main Outcomes and Measures  Annual country-specific late preterm (34-36 weeks) and early term (37-38 weeks) birth rates.

Results  The study population included 2 415 432 Canadian births in 2006-2014 (4.8% late preterm; 25.3% early term); 305 947 Danish births in 2006-2010 (3.6% late preterm; 18.8% early term); 571 937 Finnish births in 2006-2015 (3.3% late preterm; 16.8% early term); 468 954 Norwegian births in 2006-2013 (3.8% late preterm; 17.2% early term); 737 754 Swedish births in 2006-2012 (3.6% late preterm; 18.7% early term); and 25 788 558 US births in 2006-2014 (6.0% late preterm; 26.9% early term). Late preterm birth rates decreased in Norway (3.9% to 3.5%) and the United States (6.8% to 5.7%). Early term birth rates decreased in Norway (17.6% to 16.8%), Sweden (19.4% to 18.5%), and the United States (30.2% to 24.4%). In the United States, early term birth rates decreased from 33.0% in 2006 to 21.1% in 2014 among births with clinician-initiated obstetric intervention, and from 29.7% in 2006 to 27.1% in 2014 among births without clinician-initiated obstetric intervention. Rates of clinician-initiated obstetric intervention increased among late preterm births in Canada (28.0% to 37.9%), Denmark (22.2% to 25.0%), and Finland (25.1% to 38.5%), and among early term births in Denmark (38.4% to 43.8%) and Finland (29.8% to 40.1%).

Conclusions and Relevance  Between 2006 and 2014, late preterm and early term birth rates decreased in the United States, and an association was observed between early term birth rates and decreasing clinician-initiated obstetric interventions. Late preterm births also decreased in Norway, and early term births decreased in Norway and Sweden. Clinician-initiated obstetric interventions increased in some countries but no association was found with rates of late preterm or early term birth.

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