title: How much variation in CS rates can be explained by case mix differences?
abstract: OBJECTIVE
  To quantify the amount of variation in caesarean section (CS) rates between maternity units explained by case mix differences.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  All 216 maternity units in England and Wales.
  
  
  METHODS
  Women giving birth at these maternity units between May and July 2000.
  
  
  METHODS
  Logistic regression models were developed to investigate the relationship between case mix characteristics, and odds of (i) CS before labour, (ii) CS in labour. Using these results, overall CS rates standardised for case mix were calculated for each maternity unit. Random-effects meta-analysis was used to examine heterogeneity between maternity units.
  
  
  METHODS
  CS before labour and CS during labour.
  
  
  RESULTS
  Adjustment for case mix differences between maternity units explained 34% of the variance in CS rates. Odds of CS (before and in labour) increased with maternal age. Women from ethnic minority groups had lower odds of CS before labour, and increased odds of CS in labour. Women with a previous vaginal delivery had lower odds of CS, although the magnitude of this for CS before and in labour is markedly different.
  
  
  CONCLUSIONS
  Case mix adjustment is important to enable understanding of the factors that influence the CS rate. These include organisational and staffing levels as well as women's preferences for childbirth and clinician's attitudes. An understanding of how these factors influence the CS rate is essential for evaluation of quality and appropriateness of obstetric care provided to women.
authors.affiliation: National Collaborating Centre for Women's and Children's Health, 27 Sussex Place, London NW1 4RG, UK.
authors.forename: S
authors.initials: S
authors.lastname: Paranjothy
authors.forename: C
authors.initials: C
authors.lastname: Frost
authors.forename: J
authors.initials: J
authors.lastname: Thomas
mesh_terms: D000293:Adolescent; D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data*; D002648:Child; D003430:Cross-Sectional Studies; D003953:Diagnosis-Related Groups; D004739:England; D005260:Female; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D012044:Regression Analysis; D014852:Wales