title: Population-based standardization (PBS) of institutional cesarean delivery rates.
abstract: BACKGROUND
  Raw cesarean section rates are often compared among institutions with different patient populations. The purpose of this study was to develop an easily reproducible mathematical model that allows comparisons of cesarean delivery rates across different patient populations and institutions.
  
  
  METHODS
  We first calculated three institution's cesarean delivery rates for each of ten groups of patients based on age and parity. The population based adjusted total cesarean delivery rate was then calculated for each institution based on the distribution of patients in the 2004 national birth data (n=4,097,029) but using the three institutions' individual cesarean delivery rates.
  
  
  RESULTS
  The adjusted for age and parity cesarean delivery rate was significantly lower from raw cesarean delivery rates in two of the three institutions (A: 28.2% adjusted vs. 36.5% raw; P=0; B: 28.2% adjusted vs. 30.4% raw, P=0.0411; C: 28.7% adjusted vs. 29.7% raw, NS) reflecting the older and more nulliparous patients in these two institutions.
  
  
  CONCLUSIONS
  Our study confirms that raw cesarean delivery rate should not be used to compare quality of care within and among different institutions unless they are adjusted for different patient characteristics. We believe that using unadjusted cesarean delivery rates without appropriate adjustments in quality assurance and when comparing data with other institutions and the national rate is erroneous and misleading.
authors.affiliation: Department of Obstetrics and Gynecology Weill Medical College of Cornell University 525 East 68th Street Suite J-130 New York NY 10065 USA. amg2002@med.cornell.edu
authors.forename: Amos
authors.initials: A
authors.lastname: Grünebaum
authors.forename: Frank
authors.initials: F
authors.lastname: Chervenak
authors.forename: Daniel
authors.initials: D
authors.lastname: Skupski
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000592:standards* / Q000706:statistics & numerical data*; D005260:Female; D006761:Hospitals / Q000592:standards; D006801:Humans; D008962:Models, Theoretical; D009518:New York; D010298:Parity; D011247:Pregnancy; D011785:Quality Assurance, Health Care / Q000592:standards*; D012015:Reference Standards; D015203:Reproducibility of Results; D012189:Retrospective Studies