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Linkage of Maternity Hospital Episode Statistics data to birth registration and notification records for births in England 2005-2014: methods. A population-based birth cohort study
  1. Nirupa Dattani1,
  2. Alison Macfarlane2
  1. 1 Centre for Maternal and Child Health Research, City, University of London, London, UK
  2. 2 Centre for Maternal and Child Health Research, City, University of London, London, UK
  1. Correspondence to Ms Nirupa Dattani; n.dattani.1{at}


Introduction Maternity Hospital Episode Statistics (HES) data for 2005–2014 were linked to birth registration and birth notification data (previously known as NHS Numbers for Babies or NN4B) to bring together some key demographic and clinical data items not otherwise available at a national level. The linkage algorithm that was previously used to link 2005–2007 data was revised to improve the linkage rate and reduce the number of duplicate HES records.

Methods Birth registration and notification linked records from the Office for National Statistics (‘ONS birth records’) were further linked to Maternity HES delivery and birth records using the NHS Number and other direct identifiers if the NHS Number was missing.

Results For the period 2005–2014, over 94% of birth registration and notification records were correctly linked to HES delivery records. Two per cent of the ONS birth records were incorrectly linked to the HES delivery record and 5% of ONS birth records were linked to more than one HES delivery record. Therefore, a considerable amount of time was spent in quality assuring these files.

Conclusion The linkage rate for birth registration and notification records to HES delivery records steadily improved from 2005 to 2014 due to improvement in the quality and completeness of patient identifiers in both HES and birth notification data.

  • births
  • linkage
  • national data

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  • Contributors Nirupa Dattani was responsible for the linkage methodology and writing first draft of the paper, and Professor Alison Macfarlane re-drafted and provided final approval of the version to be published. We agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

  • Funding This work was supported by the National Institute for Health Research. HS&DR Programme, project number HS&DR 12/136/93. Project title: ‘Births and their outcome: analysing the daily, weekly and yearly cycle and their implications for the NHS’.

  • Disclaimer The views and opinions expressed here are those of the authors and do not necessarily reflect those of the HS&DR programme, NIHR, NHS or the Department of Health. The data were processed in the secure environment of the Office for National Statistics’ Virtual Microdata Laboratory and the following disclaimer applies: This work contains statistical data from ONS which is Crown Copyright. The use of the ONS statistical data in this work does not imply the endorsement of the ONS in relation to the interpretation or analysis of the statistical data. This work uses research datasets which may not exactly reproduce National Statistics aggregates.

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval East London and City Local Research Ethics Committee 1 and its successors.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement The authors do not have permission to supply data or identifiable information to third parties, including other researchers but they have permission under Section 251 of the Health Service (Control of Patient Information) Regulations 2002 to analyse patient identifiable data for England and Wales without consent and create a research database which could be accessed by other researchers using the VML at the Office for National Statistics. Anyone wishing to access the linked datasets for research purposes should apply to the Office for National Statistics and NHS Digital as well as to the Confidentiality Advisory Group of the Health Research Authority to access patient identifiable data without consent. We are currently in discussion with ONS and NHS Digital about the application process.

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