title: Maternal clinical diagnoses and hospital variation in the risk of cesarean delivery: analyses of a National US Hospital Discharge Database.
abstract: BACKGROUND
  Cesarean delivery is the most common inpatient surgery in the United States, where 1.3 million cesarean sections occur annually, and rates vary widely by hospital. Identifying sources of variation in cesarean use is crucial to improving the consistency and quality of obstetric care. We used hospital discharge records to examine the extent to which variability in the likelihood of cesarean section across US hospitals was attributable to individual women's clinical diagnoses.
  
  
  RESULTS
  Using data from the 2009 and 2010 Nationwide Inpatient Sample from the Healthcare Cost and Utilization Project--a 20% sample of US hospitals--we analyzed data for 1,475,457 births in 1,373 hospitals. We fitted multilevel logistic regression models (patients nested in hospitals). The outcome was cesarean (versus vaginal) delivery. Covariates included diagnosis of diabetes in pregnancy, hypertension in pregnancy, hemorrhage during pregnancy or placental complications, fetal distress, and fetal disproportion or obstructed labor; maternal age, race/ethnicity, and insurance status; and hospital size and location/teaching status. The cesarean section prevalence was 22.0% (95% confidence interval 22.0% to 22.1%) among women with no prior cesareans. In unadjusted models, the between-hospital variation in the individual risk of primary cesarean section was 0.14 (95% credible interval 0.12 to 0.15). The difference in the probability of having a cesarean delivery between hospitals was 25 percentage points. Hospital variability did not decrease after adjusting for patient diagnoses, socio-demographics, and hospital characteristics (0.16 [95% credible interval 0.14 to 0.18]). A limitation is that these data, while nationally representative, did not contain information on parity or gestational age.
  
  
  CONCLUSIONS
  Variability across hospitals in the individual risk of cesarean section is not decreased by accounting for differences in maternal diagnoses. These findings highlight the need for more comprehensive or linked data including parity and gestational age as well as examination of other factors-such as hospital policies, practices, and culture--in determining cesarean section use. Please see later in the article for the Editors' Summary.
authors.affiliation: Division of Health Policy and Management, University of Minnesota School of Public Health, Minneapolis, Minnesota, United States of America.
authors.forename: Katy B
authors.initials: KB
authors.lastname: Kozhimannil
authors.affiliation: Department of Social and Behavioral Sciences, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Mariana C
authors.initials: MC
authors.lastname: Arcaya
authors.affiliation: Department of Social and Behavioral Sciences, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: S V
authors.initials: SV
authors.lastname: Subramanian
mesh_terms: D002585:Cesarean Section / Q000706:statistics & numerical data*; D016208:Databases, Factual; D036861:Delivery, Obstetric / Q000706:statistics & numerical data; D005260:Female; D006761:Hospitals / Q000706:statistics & numerical data; D006801:Humans; D007744:Obstetric Labor Complications / Q000175:diagnosis* / Q000453:epidemiology / Q000601:surgery; D011247:Pregnancy; D012307:Risk Factors