Inter-Hospital Comparison of Caesarean Delivery Rates Figure 1. Funnel plot showing the relationship between the number of deliveries and NTCS CD rates in the hospitals of Tuscany. Dashed lines indicate the 95% and 99.8% CI for the CD rates. doi:10.1371/journal.pone.0028060.g001 temporal or geographical variations at national or regional level, healthcare outcomes and quality of care [7]. Lastly, since the impact of variables used for risk adjustment may vary across populations, generalization of our results should be done with caution. Taking into account differences in case mix across hospitals is fair and appropriate, however, we submit that crude NTCS measures can be reliably used for inter-hospital comparison. NTCS CD rates are easily retrieved from birth certificate or vital statistics systems in many countries, thereby avoiding linkage procedures with other datasets that contain more detailed clinical information. Since in our population adjusted and crude NTCS CD rates lead to consistent hospital rankings and crude NTCS rates are highly correlated with adjusted CD rates, the contention that differences in case mix are responsible for differences in CD rates could be minimized. In addition, by using this measure, a substantial proportion of primary CD are captured. US and European studies have shown that providing feedback to caregivers on their own performances relative to their peers can significantly reduce CD rates [30,31]. Efforts to reduce primary CD rates will, in turn, have the added benefit of reducing the total number of repeated CD. Our study contributes to identifying an efficient way to make inter-hospital comparisons using routinely collected data. References 1. Belizan J, Althabe F, Cafferata ML (2007) Health consequences of the increasing caesarean section rates. Epidemiology 18: 485–486. 2. Chaillet N, Dumont A (2007) Evidence-based strategies for reducing cesarean section rates: a meta-analysis. Birth 34: 53–64. 3. Main EK, Bingham D (2008) Quality improvement in maternity care: promising approaches from the medical and public health perspectives. Curr Opin Obstet Gynecol 20: 574–80. 4. Main EK, Moore D, Farrell B, Schimmel LD, Altman RJ, et al. (2006) Is there a useful cesarean birth measure? Assessment of the nulliparous term singleton vertex cesarean birth rate as a tool for obstetric quality improvement. Am J Obstet Gynecol 194: 1644–51. In conclusion, our findings show that risk adjustment is warranted for inter-hospital comparisons of primary CD rates, but is less compelling for NTCS CD rates. Inter-hospital comparison of NTCS CD rates has the potential to identify overuse of CD in low-risk primigravidas and to inform attempts to reduce hospital CD rates. Supporting Information Table S1 Crude and adjusted primary CD rates and RR by hospital in Emilia Romagna and Tuscany Regions. (DOC) Table S2 Crude and adjusted NTCS CD rates and RR by Hospital in Emilia Romagna and Tuscany Regions. (DOC) Author Contributions Conceived and designed the experiments: ES SN MPF. Analyzed the data: ES PR EC CS. Wrote the paper: ES GP. Contributed to the acquisition of data: GP MT. Contributed to the interpretation of data: EC CS ED. Critically revised the manuscript: PR CS SN ED MT MPF. Approved the final version of the manuscript: ES PR EC GP CS SN ED MT MPF. 5. Aron DC, Harper DL, Shepardson LB, Rosenthal GE (1998) Impact of risk- adjusting cesarean delivery rates when reporting hospital performance. JAMA 279: 1968–72. 6. Fantini MP, Stivanello E, Frammartino B, Barone AP, Fusco D, et al. (2006) Risk adjustment for inter-hospital comparison of primary cesarean section rates: need, validity and parsimony. BMC Health Serv Res 15: 100. 7. Korst LM, Gornbein JA, Gregory KD (2005) Rethinking the cesarean rate: how pregnancy complications may affect inter-hospital comparisons. Med Care 43: 237–45. 8. American College of Obstetricians and Gynecologists (2000) Evaluation of cesarean delivery. Washington, DC: ACOG. PLoS ONE | www.plosone.org 4 November 2011 | Volume 6 | Issue 11 | e28060