title: Case mix adjustment of health outcomes, resource use and process indicators in childbirth care: a register-based study.
abstract: Unwarranted variation in care practice and outcomes has gained attention and inter-hospital comparisons are increasingly being used to highlight and understand differences between hospitals. Adjustment for case mix is a prerequisite for meaningful comparisons between hospitals with different patient populations. The objective of this study was to identify and quantify maternal characteristics that impact a set of important indicators of health outcomes, resource use and care process and which could be used for case mix adjustment of comparisons between hospitals.
  
  
  
  In this register-based study, 139 756 deliveries in 2011 and 2012 were identified in regional administrative systems from seven Swedish regions, which together cover 67 % of all deliveries in Sweden. Data were linked to the Medical birth register and Statistics Sweden's population data. A number of important indicators in childbirth care were studied: Caesarean section (CS), induction of labour, length of stay, perineal tears, haemorrhage > 1000 ml and post-partum infections. Sociodemographic and clinical characteristics deemed relevant for case mix adjustment of outcomes and resource use were identified based on previous literature and based on clinical expertise. Adjustment using logistic and ordinary least squares regression analysis was performed to quantify the impact of these characteristics on the studied indicators.
  
  
  
  Almost all case mix factors analysed had an impact on CS rate, induction rate and length of stay and the effect was highly statistically significant for most factors. Maternal age, parity, fetal presentation and multiple birth were strong predictors of all these indicators but a number of additional factors such as born outside the EU, body mass index (BMI) and several complications during pregnancy were also important risk factors. A number of maternal characteristics had a noticeable impact on risk of perineal tears, while the impact of case mix factors was less pronounced for risk of haemorrhage > 1000 ml and post-partum infections.
  
  
  
  Maternal characteristics have a large impact on care process, resource use and outcomes in childbirth care. For meaningful comparisons between hospitals and benchmarking, a broad spectrum of sociodemographic and clinical maternal characteristics should be accounted for.
authors.affiliation: Medical Management Centre, Karolinska Institutet, Tomtebodavägen 18 A, 171 77, Stockholm, Sweden. johan.mesterton@ki.se.|Ivbar Institute, Stockholm, Sweden. johan.mesterton@ki.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Mesterton
authors.affiliation: Medical Management Centre, Karolinska Institutet, Tomtebodavägen 18 A, 171 77, Stockholm, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Lindgren
authors.affiliation: Departement of Obstetrics and Gynecology, Akademiska Hospital, Uppsala, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Ekenberg Abreu
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Clinical Sciences, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Ladfors
authors.affiliation: Department of Obstetrics and Gynecology, Skane University Hospital, Lund, Sweden.
authors.forename: Monica
authors.initials: M
authors.lastname: Lilja
authors.affiliation: Department of Obstetrics and Gynecology, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Sissel
authors.initials: S
authors.lastname: Saltvedt
authors.affiliation: Medical Management Centre, Karolinska Institutet, Tomtebodavägen 18 A, 171 77, Stockholm, Sweden.|Department of Women and Child Health, Karolinska Institutet, Stockholm, Sweden.|Stockholm County Council, Stockholm, Sweden.
authors.forename: Isis
authors.initials: I
authors.lastname: Amer-Wåhlin
mesh_terms: D002585:Cesarean Section / Q000706:statistics & numerical data*; D036861:Delivery, Obstetric / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006295:Health Resources / Q000706:statistics & numerical data*; D006801:Humans; D007746:Labor Presentation; D007751:Labor, Induced / Q000706:statistics & numerical data; D007902:Length of Stay / Q000706:statistics & numerical data; D008423:Maternal Age; D010043:Outcome and Process Assessment, Health Care; D010298:Parity; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data; D012042:Registries; D020379:Risk Adjustment / Q000706:statistics & numerical data*; D012307:Risk Factors; D013548:Sweden
keywords: Caesarean section; Case mix adjustment; Childbirth; Length of stay; Outcomes; Value-based health care