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.

Methods and findings: 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.

Figure 1. Funnel plots of hospital cesarean rates, overall and for subgroups of women.

Funnel plots show how each individual institution (blue dot) performs compared to the mean (red) and control limits (the 99% prediction interval around the calculated mean). The upper control limit is shown as purple and the lower control limit is shown as green. Cesarean rates for (A) all women, (B) women with no prior cesarean, (C) lower risk women, and (D) higher risk women.

Figure 2. Between-hospital variation in cesarean deliveries overall and for subgroups of women, null and fully adjusted models.

Populations include all births, all births to women with no prior cesarean delivery, all births to lower risk women (those with term, singleton, vertex pregnancies and no prior cesarean delivery), and all births to higher risk women (those with a preterm, multiple gestation, or nonvertex pregnancy or prior cesarean delivery). Factors included in adjusted models are diagnosis of maternal hypertension, diabetes, hemorrhage or placental complications, fetal distress, and fetal disproportion or obstructed labor; maternal age, race/ethnicity, and insurance status; hospital bed size and location/teaching status; and state-level fixed effects.