either the mother/primary caregiver or the child, has provided data. Of these enrolled participants, ALSPAC has collected data relating directly to 14 009 (71.5% of 19 600 eligible live births) children, through self-reported data from the child or data provided about the child by the biological mother/primary caregiver. The ‘eligible sample’ remains eligible regardless of their participation history or movement away from the study area (questionnaires and invitation to clinical assessments are sent worldwide); if participants withdraw from the study, they remain eligible and are free to re-enrol into the study if they wish (32 families re-joined the study in this way by the age of 18 years).
