Risk Adjustment for Inter-Hospital Comparison of Caesarean Delivery Rates in Low-Risk Deliveries Elisa Stivanello1*, Paola Rucci1, Elisa Carretta1, Giulia Pieri1, Chiara Seghieri2, Sabina Nuti2, Eugene Declercq3, Martina Taglioni4, Maria Pia Fantini1 1 Department of Medicine and Public Health – Alma Mater Studiorum University of Bologna, Bologna, Italy, 2 Laboratorio MeS, Scuola Superiore Sant’Anna, Pisa, Italy, 3 Department of Community Health Sciences, Boston University School of Public Health, Boston, Massachusetts, United States of America, 4 Medical Directorate, Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy Abstract Background: Caesarean delivery (CD) rates have been frequently used as quality measures for maternity service comparisons. More recently, primary CD rates (CD in women without previous CD) or CD rates within selected categories such as nulliparous, term, cephalic singleton deliveries (NTCS) have been used. The objective of this study is to determine the extent to which risk adjustment for clinical and socio-demographic variables is needed for inter-hospital comparisons of CD rates in women without previous CD and in NTCS deliveries. Methods: Hospital discharge records of women who delivered in Emilia-Romagna Region (Italy) from January, 2007 to June 2009 and in Tuscany Region for year 2009 were linked with birth certificates. Adjusted RRs of CD in women without a previous Caesarean and NTCS were estimated using Poisson regression. Percentage differences in RR before and after adjustment were calculated and hospital rankings, based on crude and adjusted RRs, were examined. Results: Adjusted RR differed substantially from crude RR in women without a previous Caesarean and only marginally in NTCS group. Hospital ranking was markedly affected by adjustment in women without a previous CD, but less in NTCS. Conclusion: Risk adjustment is warranted for inter-hospital comparisons of primary CD rates but not for NTCS CD rates. Crude NTCS CD rates are a reliable estimate of adjusted NTCS CD. Citation: Stivanello E, Rucci P, Carretta E, Pieri G, Seghieri C, et al. (2011) Risk Adjustment for Inter-Hospital Comparison of Caesarean Delivery Rates in Low-Risk Deliveries. PLoS ONE 6(11): e28060. doi:10.1371/journal.pone.0028060 Editor: Eduard Gratacos, Hospital Clinic-University of Barcelona, Spain Received July 22, 2011; Accepted October 31, 2011; Published November 23, 2011 Copyright: 2011 Stivanello et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors have no support or funding to report. Competing Interests: The authors have declared that no competing interests exist. * E-mail: elisa.stivanello2@unibo.it Introduction The Caesarean delivery (CD) rate continues to rise in many countries worldwide even though this increase does not appear to be associated with improvement in maternal and perinatal mortality or morbidity [1]. Several studies suggested the benefit of multifaceted intervention, based on audit and detailed feedback activities, in improving clinical practice and effectively and safely reducing unnecessary CD [2,3]. The most frequently used quality indicator to evaluate and compare maternal services is the overall CD rate [4–7]. However, recently this measure has been questioned and other measures have been introduced for audit activities and inter-hospital comparison [8]. Because of the existing controversy about safety of vaginal birth after a previous CD, several studies have recommended focusing quality efforts on primary CD rates (CD in women without previous CD) [4,8–11]. Furthermore, based on evidence suggesting that non-vertex and multiple births may have better outcomes with CD [12,13], some authors omitted these categories from the calculation of CD rates and examined only nulliparous, term, cephalic singleton deliveries (NTCS) [4,9,11,13,14]. This group accounts for a large proportion of CD and includes potentially lower-risk pregnancies [14]. In addition, NTCS is a group where efforts to reduce CD rates would lessen the need for repeat CD in subsequent pregnancies. Nevertheless, socio-demographic characteristics and/or clinical risk factors for CD might vary across hospitals. The use of unadjusted CD rates has been questioned and case-mix adjust- ment has been recommended for audit and inter-hospital comparisons of overall and primary CD rates [5,6,8,15–17], but evidence about the need to use adjusted models for comparison of NTCS CD rates is limited [9,14]. The aim of this study is to determine the extent to which adjustment for clinical and socio-demographic variables of the mother and the foetus enhances inter-hospital comparisons of primary and NTCS CD rates. Methods For the purpose of this study, anonymised routine data obtained through record linkage of birth certificates and hospital discharge records of Emilia Romagna and Tuscany Regions (Italy) were used. The Emilia Romagna Region has 4.4 million inhabitants and approximately 40,000 births per year in 31 birth units. Tuscany Region has 3.7 million inhabitants and about 28,000 births per year in 34 birth units. PLoS ONE | www.plosone.org 1 November 2011 | Volume 6 | Issue 11 | e28060