The Avon Longitudinal Study of Parents and Children (ALSPAC) is a prospective population-based study in England [19]. All pregnant women resident in the Avon area with an expected delivery date between April 1991 and December 1992 were invited to participate. Around 85 % of all eligible women participated, providing a cohort of 14,541 pregnancies. ALSPAC participants were broadly representative of the local population of mothers with infants and comparable against national census data although they were slightly more likely to be Caucasian, married or cohabiting, home owner-occupiers, and have a car in the household (further details at http://www.alspac.bris.ac.uk and http://www.bristol.ac.uk/alspac/researchers/resources-available/cohort/represent/). Detailed information on the cohort (mothers and children) has been obtained through questionnaires completed at regular intervals during the pregnancy and since the birth. Please note that the study website contains details of all the data that are available through a fully searchable data dictionary (http://www.bris.ac.uk/alspac/researchers/data-access/data-dictionary/). Ethical approval for the study was obtained from the ALSPAC Ethics and Law Committee and the Local Research Ethics Committees.
