Variation in hospital caesarean section rates for women with at least one previous caesarean section: a population based cohort study

Schemann et al. BMC Pregnancy and Childbirth (2015) 15:179 DOI 10.1186/s12884-015-0609-x RESEARCH ARTICLE Open Access Variation in hospital caesarean section rates for women with at least one previous caesarean section: a population based cohort study Kathrin Schemann1,2*, Jillian A. Patterson1, Tanya A. Nippita1,3, Jane B. Ford1 and Christine L. Roberts1 Abstract Background: Internationally, repeat caesarean sections make the largest contribution to overall caesarean section rates and inter-hospital variation has been reported. The aim of this study was to determine if casemix and hospital factors explain variation in hospital rates of repeat caesarean sections and whether these rates are associated with maternal and neonatal morbidity. Methods: This population-based record linkage study utilised data from New South Wales, Australia between 2007 and 2011. The study population included maternities with any previous caesarean section(s) and were singleton, cephalic and ≥37 weeks’ gestation (Robson Group 5). Multilevel regression models were used to examine variation in hospital rates of ‘planned repeat caesarean section’ and, among women who planned a vaginal birth, ‘intrapartum caesarean section’. We assessed associations between risk-adjusted hospital rates of planned and intrapartum caesarean sections and rates of casemix adjusted maternal and neonatal morbidity, postpartum haemorrhage and Apgar score <7 at five minutes. Results: Of 61894 maternities with a previous caesarean section in 81 hospitals, 82.1 % resulted in a caesarean section (72.7 % planned and 9.4 % unplanned intrapartum caesareans) and 17.9 % in vaginal birth. Observed hospital rates of planned caesarean sections ranged from 50.7 % to 98.4 %. Overall 49.0 % of between-hospital variation in planned repeat caesarean section rates was explained by patient (17.3 %) and hospital factors (31.7 %). Increased odds of planned caesarean section were associated with private hospital status and lower hospital propensity for vaginal birth after caesarean. There were no associations between hospital rates of planned repeat caesarean section and adjusted morbidity rates. Among women who intended a vaginal birth, the observed rates of intrapartum caesarean section ranged from 12.9 % to 71.9 %. In total, 27.5 % of between-hospital variation in rates of intrapartum caesarean section was explained by patient (19.5 %) and hospital factors (8.0 %). The adjusted morbidity rates differed among hospital intrapartum caesarean section rates, but were influenced by a few hospitals with outlying morbidity rates. Conclusions: Among women with at least one previous caesarean section, less than half of the variation in hospital caesarean section rates was explained by differences in hospital’s patient characteristics and practices. Strategies aimed at modifying caesarean section rates for these women should not affect morbidity rates. * Correspondence: 1 Clinical and Population Perinatal Health Research, Kolling Institute of Medical Research, University of Sydney at Royal North Shore Hospital, St Leonards, NSW 2065, Australia 2 NSW Biostatistics Training Program, NSW Ministry of Health, North Sydney, NSW 2060, Australia Full list of author information is available at the end of the article © 2015 Schemann et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Schemann et al. BMC Pregnancy and Childbirth (2015) 15:179 Background Internationally, caesarean section rates have increased by 50 % or more over the last decade, with rates in the USA, UK and Australia peaking at 26.2 %, 31.3 % and 32.3 %, respectively [1–3]. The lack of availability of caesarean section in developing countries contributes to significant preventable maternal and perinatal morbidity and mortality [4]; yet in developed countries, rising caesarean section rates have not been accompanied by improved perinatal outcomes [5]. In 1985, the World Health Organization recommended a rate between 10 % and 15 % [6], and in 2009 acknowledged that it is important for the appropriate parturient to receive the optimal labour interventions, balancing the risks and benefits of each intervention [7]. Caesarean sections for women with at least one previous caesarean section make an important contribution to the historic rise in the overall caesarean section rate [8, 9]. In high income countries, Group 5 (multiparous women with at least one caesarean section and a single cephalic pregnancy at ≥37 weeks) [10] of the Robson classification for caesarean sections make the largest contribution to overall caesarean section rates [10–13]. This heterogenous group includes women with differing onsets of labour [10, 14–17], women with and without a previous vaginal delivery and women with one or more previous caesarean sections [14, 15, 18, 19]. To our knowledge, only one previous study examined adjusted hospital caesarean section rates for Robson Group 5 and identified large, unexplained variation between hospital rates for this group, despite adjustment for a limited number of case-mix factors (maternal age, country of birth of the mother, parity, maternal smoking, diabetes and hypertension) [11]. Variation in hospital caesarean section rates can be due to various factors including differences in patient characteristics or preferences, access to care, clinician behavior and hospital culture or policy. With sufficient data available on individual and hospital characteristics, variation due to known casemix and hospital factors can be accounted for, and the remaining ‘unexplained’ variation quantified. This ‘unexplained’ variation represents the contribution of unmeasured factors which result in women with similar characteristics having different outcomes depending on hospital of care [20, 21]. Unexplained variation in practice is important where it influences health care costs without improving outcomes, and raises questions about the appropriateness of particular hospital practices [22]. However, the previous study lacked information about differences in maternal and infant outcomes or evaluation of hospital characteristics that may contribute to the variation. Clinical factors such as offering trial of labour may also contribute to the variation in elective repeat caesarean section rates and subanalysis of this Page 2 of 15 group by onset of labour has been suggested [17]. Therefore, the aims of this study were, among women with at least one previ (...truncated)