'Risk-Adjusted' Cesarean Delivery Rates
ABSTRACT & COMMENTARY
Synopsis: Comparisons of hospitals based on cesarean delivery rates that have not been adjusted for clinical factors may provide patients and insurers with misleading information.
Source: Aron DC, et al. JAMA 1998;279:1968-1972.
Because the quality of care provided by hospitals and health plans is often judged on the basis of the cesarean delivery rate, with the assumption being made that lower rates indicate better care, Aron and associates examined the cesarean delivery rates in 21 hospitals in Cleveland, Ohio, before and after adjusting for important clinical risk factors that influence the likelihood of cesarean delivery. The medical records of 26,127 women who delivered between January 1993 and June 1995 and who had not had a prior cesarean birth were reviewed. The clinical risks factors included in the multivariable risk-adjustment model used in this study included the patient's age; nulliparity; important medical conditions, such as diabetes mellitus; conditions developing during pregnancy, such as pregnancy-induced hypertension; prolonged gestation and preterm birth; multiple gestation; birth weight more than 4000 g; obstetrical conditions, such as breech presentation; and placenta previa; maternal blood pressure on admission; and fetal heart rate. The number of deliveries per hospital ranged from 340 to 8933, with a median of 2311. Five hospitals were classified as teaching institutions, including four with accredited residency programs in obstetrics and gynecology. The predicted risk for cesarean delivery was calculated for each patient and then aggregated to determine the mean predicted risk for cesarean delivery for each hospital. The risk-adjusted hospital cesarean delivery rates were then compared to the actual rates.
The overall cesarean delivery rate in the 21 study hospitals was 15.9%, with a range of 6.3-26.5%. The adjusted rates varied from 8.4% to 22%, with an average adjustment of 2% or more for 10 hospitals. Before adjustment, seven hospitals were considered to be outliers, with four having significantly higher or lower rates than the overall rate observed. Adjustment changed the outlier status for five hospitals, including two that changed from outliers to nonoutliers, two that changed from nonoutliers to outliers, and one that changed from being a high outlier to a low outlier. Of the risk factors used in the adjustment process, the highest risks for cesarean delivery were associated with breech presentation, face or transverse presentation, placenta previa, umbilical cord prolapse, and placental abruption. The odds ratio for cesarean delivery in nulliparous patients was 5.39.
Aron et al conclude that comparisons of hospitals based on cesarean delivery rates that have not been adjusted for clinical factors may provide patients and insurers with misleading information.
COMMENT BY STEVEN G. GABBE, MD
For patients, insurance companies, hospitals, and health care providers, clinical outcomes and quality improvement have become important and appropriate focuses for our work. Cesarean delivery rates are often used to compare the quality of obstetric care in hospitals and among physicians. When these comparisons are made, it is important that apples are compared to apples and oranges to oranges. This important study is one of the first to do that. Using data from a single large metropolitan area, Aron et al have shown that cesarean delivery rates can vary widely from institution to institution and, most importantly, that after adjustment for clinical risk factors known to be associated with a higher risk of cesarean delivery, significant changes in the predicted rate of cesarean delivery for an institution are observed. In fact, the correlation between unadjusted and adjusted hospital rankings in this study was "only modest." Breech presentation was associated with the highest risk for cesarean delivery, and, of note, the frequency of breech presentation varied more than three-fold among the hospitals. Aron et al did not include dystocia as a risk factor because of the lack of a clear definition of this problem. Data were not provided on the risk of cesarean delivery associated with low birth weight infants (less than 1500 g) or with intrapartum transfers. The highest cesarean delivery rates are often found in patients with these risk factors.
I believe this article should be widely circulated and read by all of the participants in the healthcare process noted, so that we can more objectively discuss the quality of care as reflected by the cesarean delivery rate.
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