title: 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.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  Use of clinician-initiated obstetric intervention (either labor induction or prelabor cesarean delivery) during delivery.
  
  
  METHODS
  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
  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.
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Richards
authors.affiliation: Departments of Pediatrics and of Epidemiology, Biostatistics and Occupational Health, McGill University Faculty of Medicine, Montreal, Quebec, Canada.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kramer
authors.affiliation: Centre for Chronic Disease Prevention, Surveillance and Epidemiology Division, Public Health Agency of Canada, Ottawa, Ontario, Canada.
authors.forename: Paromita
authors.initials: P
authors.lastname: Deb-Rinker
authors.affiliation: Centre for Chronic Disease Prevention, Surveillance and Epidemiology Division, Public Health Agency of Canada, Ottawa, Ontario, Canada.
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Rouleau
authors.affiliation: Section of Social Medicine, University of Copenhagen, and Methods and Analysis, Statistics, Denmark, Copenhagen, Denmark.
authors.forename: Laust
authors.initials: L
authors.lastname: Mortensen
authors.affiliation: Information Services Department, National Institute for Health and Welfare, Helsinki, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Gissler
authors.affiliation: Departments of Global Public Health and Primary Care and Clinical Sciences, University of Bergen, Norway7Department of Obstetrics and Gynecology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Nils-Halvdan
authors.initials: NH
authors.lastname: Morken
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Norway.
authors.forename: Rolv
authors.initials: R
authors.lastname: Skjærven
authors.affiliation: Clinical Epidemiology Unit, T2, Department of Medicine Solna, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Sven
authors.initials: S
authors.lastname: Cnattingius
authors.affiliation: Clinical Epidemiology Unit, T2, Department of Medicine Solna, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Johansson
authors.affiliation: INSERM UMR 1153, Center for Epidemiology and Statistics Sorbonne Paris Cité, Paris Descartes University, Paris, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Delnord
authors.affiliation: Department of Obstetrics and Gynecology and Women's Health, Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, New York.
authors.forename: Siobhan M
authors.initials: SM
authors.lastname: Dolan
authors.affiliation: Department of Social Medicine, National Center for Child Health and Development, Tokyo, Japan.
authors.forename: Naho
authors.initials: N
authors.lastname: Morisaki
authors.affiliation: Departments of Pediatrics and Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Tough
authors.affiliation: INSERM UMR 1153, Center for Epidemiology and Statistics Sorbonne Paris Cité, Paris Descartes University, Paris, France.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Zeitlin
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kramer
mesh_terms: D002170:Canada / Q000453:epidemiology; D002585:Cesarean Section / Q000639:trends*; D003718:Denmark / Q000453:epidemiology; D003906:Developing Countries; D005260:Female; D005387:Finland / Q000453:epidemiology; D005865:Gestational Age; D006801:Humans; D007751:Labor, Induced / Q000639:trends*; D008423:Maternal Age; D009664:Norway / Q000453:epidemiology; D007752:Obstetric Labor, Premature / Q000453:epidemiology / Q000628:therapy*; D009774:Obstetrics / Q000639:trends; D011247:Pregnancy; D012189:Retrospective Studies; D013548:Sweden / Q000453:epidemiology; D047929:Term Birth; D014481:United States / Q000453:epidemiology