Background Supporting early-life health and development is one of the effective ways to improve population health and reduce inequalities. Monitoring child health and understanding its determinants is thus a policy-priority. In Scotland the community health index number (CHI), allocated to all individuals registered with a GP, presents an opportunity to link a wide range of information on mother and baby pairs from before birth and throughout the early years. We detail the development and characteristics of a national cohort from these linked data.

Methods The cohort comprised all births in Scotland, September 2009-March 2013, followed-up until March 2018. The following datasets were linked by the eData Research and Innovation Service: Scottish Morbidity (maternity) Inpatient/Day Case Record, Scottish Birth Records, National Records of Scotland births, General/Acute Inpatient/Day Case Records, Prescribing Information System, and Child Health Systems Programme (CHSP). These contain a wide range of information on birth, demographics, socio-economic indicators, child and maternal health, and parent health-related behaviours. Socio-economic circumstances included neighbourhood deprivation and as well as individual-level measures e.g parental occupational status, relationship status of parents. Some health measures were captured continuously through registers (e.g. prescribing for attention deficit hyperactivity disorder (ADHD) in the child and depression/anxiety among the mother; childhood immunisation; hospital admissions for unintentional injury), allowing examination of health at different points of the life-course (e.g. pre and post pregnancy) Others were recorded at developmentally-appropriate ages (e.g. smoking in pregnancy, infant feeding, cognitive, physical and socio-emotional development).

Results After removing failed linkages/cleaning variable labels, the cohort consisted of 202,757 children (97% all officially recorded births). 51.2% were male, 3% singleton births, and 44.7% first born children. 41.8% were born to mothers <25 years at first live birth, 82.9% had married/cohabiting parents and 22% had a long-term unemployed mother. Among health measures (for example), 91% had received their infant immunisations on time, 0.4% had ever been prescribed ADHD medication, and 4.9% had been admitted to hospital for an unintentional injury before school age. Most variables had no or low missing cases (e.g. mother’s social class, relationship status of parents), with some exceptions (such as heights and weights).

Discussion Ability to link across administrative datasets in Scotland allows examination of child and maternal health and important determinants across the entire early years’ period. We were unable to account for all emigration (as this relies on GP de-registration) and there may have been errors linking mothers to children, which may introduce bias.