Avon Longitudinal Study of Parents & Children (ALSPAC)

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The Avon Longitudinal Study of Parents & Children (ALSPAC) is a multi-generational, population-based prospective birth cohort study. Established in the early 90s, ALSPAC follows the lives of over 14,500 people born between April 1991 and December 1992 and their family members. Children and their families have been followed intensively, primarily with annual questionnaires, as well as clinical assessments for a sub-sample of cohort members. ALSPAC was specifically designed to understand the ways in which genetic and environmental factors interact to influence health, behaviour, and development across the lifespan.

The ALSPAC study has collected data using a range of methods. Mental health measures collected in postal questionnaires and from clinic assessments are detailed on the Catalogue.

University of Bristol

Geographic coverage - Nations

Geographic coverage - Regions
Bristol & District Health Authority (Former Avon Health Authority Area)

Start date

Catalogue record last updated


Sample type
Pregnancy cohort

Sample details
Pregnant women residing in Avon with an expected delivery date between the 1 April 1991 and the 31 December 1992 were eligible to participate.

The initial sample was recruited during Phase I, in which mothers enrolled in the study during pregnancy and then either returned at least one questionnaire or attended a "Children in Focus" clinic by 19 July 1999. This initial sample consisted of 14,541 pregnancies (14,676 foetuses, with 195 twin, 3 triplet and 1 quadruplet pregnancies), resulting in 14,062 live births. 13,988 children (cohort members) were alive at 1 year of age.

Eligible cohort members who did not join in Phase I have joined the study through major recruitment drives since the cohort members were 7 years old. A further 913 eligible cohort members have been enrolled in this way. As a result of further enrolment during Phases II (7years), III (8 years) and IV (18 years), the baseline sample consists of 15,454 pregnancies (15,589 known foetuses) and 14,901 cohort members alive at 1 year of age.

During pregnancy, partners/fathers were recruited via the mother. More recently, fathers have been recruited directly by the ALSPAC team and via the cohort members. Measures relating to cohort members’ grandparents have also been collected from the cohort members, mothers and fathers.

The study has been extended to include cohort members’ children. This study, known as ALSPAC-Generation 2 (COCO90s), is not currently included in the Catalogue, but more information is available here.

Sample size at recruitment
15,454 enrolled pregnancies
14,901 children (cohort members) alive at 1 year of age

Sample size at most recent sweep
Approximately 3,400 (2023 - Life at 27+)


Age at recruitment

Cohort year of birth
April 1991 - December 1992


Data access
Project proposal - contact study team http://www.bristol.ac.uk/alspac/researchers/access/

Genetic data collected

Linkage to administrative data
Education data
Environmental data
Health data
Social media data

HDR UK Innovation Gateway
HDR Gateway

Additional information


Also known as Children of the 90s (CO90s).

Related themes
Covid-19 data collection, Biomarkers, Cognitive measures, Diet and nutrition, Education, Ethnicity and race, Sexuality and gender identity, Housing, Socioeconomic status and deprivation, Language and literacy, Loneliness and social isolation, Neighbourhood, Physical health assessment, Political and social attitudes, Digital technology and social media, Victimisation and life events, Puberty, Reproductive health, Work and employment, Parenting and family, Sleep problems, Social care - receipt, Social care - provision, Social care - need

Key Papers

Cohort profile: the ‘children of the 90s’—the index offspring of the Avon Longitudinal Study of Parents and Children. doi.org/10.1093/ije/dys064

The Avon Longitudinal Study of Parents and Children (ALSPAC): an update on the enrolled sample of index children in 2019. doi.org/10.12688/wellcomeopenres.15132.1

Fraser et al. (2013). Cohort profile: the Avon Longitudinal Study of Parents and Children: ALSPAC mothers cohort. doi.org/10.1093/ije/dys066

Smith et al. (2021). The Avon Longitudinal Study of Parents and Children - A resource for COVID-19 research: Questionnaire data capture November 2020 – March 2021. doi.org/10.12688/wellcomeopenres.16950.1

Medical Research Council
Wellcome Trust
University of Bristol
Mental health measures timeline

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