title: Obstetrician volume as a potentially modifiable risk factor for cesarean delivery.
abstract: OBJECTIVE
  To examine the relationship between an obstetrician's delivery volume and a patient's risk for cesarean delivery.
  
  
  METHODS
  This retrospective cohort study examined patient-level and obstetrician-level data between 2000 and 2012 at a large academic hospital. All laboring patients who delivered viable, liveborn, singleton newborns (N=58,328) were included. We measured the association of delivery volume and cesarean delivery using a multivariate logistic regression. We also assessed the association of volume by calculating adjusted cesarean delivery rates using the least squares means method. These analyses were performed on the subset of nulliparous patients with term, singleton, vertex-presenting fetuses. In addition, the association of obstetrician experience was compared against delivery volume.
  
  
  RESULTS
  There was a twofold increase in the odds of cesarean delivery for patients whose obstetricians performed fewer than the median (60) number of deliveries per year (quartile 1: odds ratio 2.00, 95% confidence interval 1.68-2.38; quartile 2: odds ratio 2.73, 95% CI 2.40-3.11) as compared with quartile 4. The adjusted cesarean delivery rate decreased from 18.2% to 9.2% from the highest to lowest volume quartile (P<.001). Compared with the volume effects, an obstetrician's experience had a smaller effect on a patient's risk of cesarean delivery.
  
  
  CONCLUSIONS
  Patients delivered by obstetricians with low delivery volume are at significantly increased risk for cesarean delivery after controlling for patient and obstetrician characteristics. In contrast, obstetrician experience had a less significant effect. These findings may prompt discussions regarding the role of volume in credentialing and practice models that direct patients to obstetricians with high delivery volume.
  
  
  METHODS
  : II.
authors.affiliation: Brigham and Women's Hospital and Beth Israel Deaconess Medical Center, Boston, Massachusetts.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Clapp
authors.forename: Alexander
authors.initials: A
authors.lastname: Melamed
authors.forename: Julian N
authors.initials: JN
authors.lastname: Robinson
authors.forename: Neel
authors.initials: N
authors.lastname: Shah
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Little
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000009:adverse effects / Q000379:methods* / Q000706:statistics & numerical data*; D015331:Cohort Studies; D016001:Confidence Intervals; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D016015:Logistic Models; D015999:Multivariate Analysis; D009774:Obstetrics / Q000592:standards* / Q000639:trends; D016017:Odds Ratio; D061214:Patient Safety / Q000706:statistics & numerical data*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data; D011247:Pregnancy; D011787:Quality of Health Care; D012189:Retrospective Studies; D018570:Risk Assessment; D016896:Treatment Outcome; D016526:Workload / Q000706:statistics & numerical data*