title: Evaluating maternity care using national administrative health datasets: how are statistics affected by the quality of data on method of delivery?
abstract: BACKGROUND
  Information on maternity services is increasingly derived from national administrative health data. We evaluated how statistics on maternity care in England were affected by the completeness and consistency of data on "method of delivery" in a national dataset.
  
  
  METHODS
  Singleton deliveries occurring between April 2009 and March 2010 in English NHS trusts were extracted from the Hospital Episode Statistics (HES) database. In HES, method of delivery can be entered twice: 1) as a procedure code in core fields, and 2) in supplementary maternity fields. We examined overall consistency of these data sources at a national level and among individual trusts. The impact of different analysis rules for handling inconsistent data was then examined using three maternity statistics: emergency caesarean section (CS) rate; third/fourth degree tear rate amongst instrumental deliveries, and elective CS rate for breech presentation.
  
  
  RESULTS
  We identified 629,049 singleton deliveries. Method of delivery was not entered as a procedure or in the supplementary fields in 0.8% and 12.5% of records, respectively. In 545,594 records containing both data items, method of delivery was coded consistently in 96.3% (kappa = 0.93; p < 0.001). Eleven of 136 NHS trusts had comparatively poor consistency (<92%) suggesting systematic data entry errors. The different analysis rules had a small effect on the statistics at a national level but the effect could be substantial for individual NHS trusts. The elective CS rate for breech was most sensitive to the chosen analysis rule.
  
  
  CONCLUSIONS
  Organisational maternity statistics are sensitive to inconsistencies in data on method of delivery, and publications of quality indicators should describe how such data were handled. Overall, method of delivery is coded consistently in English administrative health data.
authors.affiliation: Office for Research and Clinical Audit, Lindsay Stewart R&D Centre, Royal College of Obstetricians and Gynaecologists, London, UK. hknight@rcog.org.uk
authors.forename: Hannah E
authors.initials: HE
authors.lastname: Knight
authors.forename: Ipek
authors.initials: I
authors.lastname: Gurol-Urganci
authors.forename: Tahir A
authors.initials: TA
authors.lastname: Mahmood
authors.forename: Allan
authors.initials: A
authors.lastname: Templeton
authors.forename: David
authors.initials: D
authors.lastname: Richmond
authors.forename: Jan H
authors.initials: JH
authors.lastname: van der Meulen
authors.forename: David A
authors.initials: DA
authors.lastname: Cromwell
mesh_terms: D059019:Clinical Coding / Q000592:standards; D016208:Databases, Factual / Q000592:standards*; D036861:Delivery, Obstetric / Q000379:methods / Q000706:statistics & numerical data*; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D008427:Maternal Health Services / Q000706:statistics & numerical data*; D009313:National Health Programs / Q000592:standards / Q000706:statistics & numerical data*; D011247:Pregnancy