The Avon Longitudinal Study of Parents and Children (ALSPAC) cohort has been described previously (Boyd et al., 2012; Fraser et al., 2012). Briefly, pregnant women in the Avon area of Southwest England with expected delivery dates between April 1, 1991 and December 31, 1992 were eligible to enroll in the study. The initial number of pregnancies enrolled, and for which the mother returned at least one questionnaire or attended a “Children in Focus” clinic, was 14,541. Additional participants have been added as recruitment efforts continue. ALSPAC parents and children have been followed longitudinally, with mothers, mothers’ partners, and children providing data through postal questionnaires and clinic visits. Ethical approval for the study was obtained from the ALSPAC Law and Ethics committee and the Local Research Ethics Committees. Additional details are available at www.alspac.bristol.ac.uk.
