title: Contribution of changing risk factors to the trend in breech presentation at term.
abstract: BACKGROUND
  Recent population-wide changes in perinatal risk factors may affect rates of breech presentation at birth, and have implications for the provision of breech services and training in breech management.
  
  
  OBJECTIVE
  To investigate whether changes in maternal and pregnancy characteristics explain the observed trend in breech presentation at term.
  
  
  METHODS
  All singleton term (≥37 week) births in New South Wales during 2002-2012 were identified through birth and associated hospital records. Annual rates of breech presentation were determined. Logistic regression modelling was used to predict expected rates of breech presentation and these were compared with observed rates over time. A priori predictors included maternal age, country of birth, parity, smoking during pregnancy, diabetes, pregnancy hypertension, placenta praevia, previous singleton term breech, previous caesarean section, infant sex, gestational age, birthweight and congenital anomalies. Hospital and Medicare data were used to assess concomitant trends in external cephalic version.
  
  
  RESULTS
  Among 914 147 singleton term births, 3.1% were breech at delivery. Rates of breech presentation declined from 3.6% in 2002 to 2.7% in 2012 (test for trend P < 0.001), but was predicted to increase from 3.6% in 2002 to 4.3% in 2012 because of increased maternal age, nulliparity, maternal diabetes, history of breech presentation and previous caesarean section. However, use of external cephalic version appears to have increased over time.
  
  
  CONCLUSIONS
  Breech presentation at delivery has decreased in New South Wales. Increased use of external cephalic version likely accounts for this decline, as changes in risk factors do not.
authors.affiliation: Clinical and Population Perinatal Health Research, The Kolling Institute, St Leonards, New South Wales, Australia.|Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Yu Sun
authors.identifier: http://orcid.org/0000-0002-4954-2658
authors.initials: YS
authors.lastname: Bin
authors.affiliation: Clinical and Population Perinatal Health Research, The Kolling Institute, St Leonards, New South Wales, Australia.|Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Roberts
authors.affiliation: Department of Obstetrics and Gynaecology, Royal North Shore Hospital, St Leonards, New South Wales, Australia.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Nicholl
authors.affiliation: Menzies Centre for Health Policy, Sydney School of Public Health, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Natasha
authors.initials: N
authors.lastname: Nassar
authors.affiliation: Clinical and Population Perinatal Health Research, The Kolling Institute, St Leonards, New South Wales, Australia.|Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Jane B
authors.initials: JB
authors.lastname: Ford
mesh_terms: D000328:Adult; D001946:Breech Presentation / Q000453:epidemiology* / Q000628:therapy*; D002585:Cesarean Section; D048909:Diabetes Complications / Q000453:epidemiology; D005260:Female; D006801:Humans; D008423:Maternal Age; D009517:New South Wales / Q000453:epidemiology; D010298:Parity; D011247:Pregnancy; D012008:Recurrence; D012307:Risk Factors; D047929:Term Birth; D014710:Version, Fetal / Q000706:statistics & numerical data / Q000639:trends*; D055815:Young Adult
keywords: breech presentation; external cephalic version; risk factors; trends