Birth cohort data linkage study

Birth cohort data linkage study

This research, undertaken by researchers at City, University of London and funded by the National Institute for Health Research, used data made available via the Office for National Statistics (ONS) Secure Research Service (SRS), which is being expanded and improved with ADR UK funding. 


When babies are born in England and Wales, data about them is recorded in three separate systems: 

  • demographic data is recorded when parents register their babies’ birth; 

  • an NHS number is recorded when the birth is notified to the NHS; and 

  • clinical data is recorded when births occur in NHS hospitals. National systems also record data about subsequent admissions of babies or mothers to hospital. 

Although analyses by day of the week had been done in the past, these were restricted to aggregated data and there was no data about the time of birth. The creation of the linked birth cohort made it possible to analyse births and their outcome by time of day as well as day of the week, for the first time. 

This birth cohort study, led by Professor Alison Macfarlane of City, University of London, linked 93% of birth registration and notification data from 2005 to 2014 with Hospital Episode Statistics (HES) delivery records. 95% of all ONS singleton birth records and 93% of multiple births overall were successfully linked to a HES record for analysis. 

The findings of this study suggest births in England and Wales follow a pattern in a regular weekly cycle, with numbers falling the lowest at weekends and on public holidays, and peaking between 9.00 and noon on all days. 

The results of the analyses of timing of birth have implications for the planning of staffing of maternity services, helping the NHS maintain a safe ’24-hour health service’ and adequately staff its wards at nights and during the weekends. 

Other researchers have started to use the linked birth cohort. The Tracking the Impact of Gestational Age on Health, Educational and Economic outcomes: A Longitudinal Record Linkage Study (TIGAR) project has been using the data about children born in 2005 and 2006 to analyse admissions of children to hospital according to gestational age at birth. A further project to link birth records of children born before and after the 2011 census to their birth records is now under way and further projects are at the planning and development stage. 

Read the findings in full. 

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