Analyses were based on 3 European population-based birth cohorts: the Portuguese Generation XXI birth cohort, the British Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort, and the French Etude des Déterminants pre et postnatals précoces du développement et de la santé de l'ENfant (EDEN) mother-child cohort. In each cohort, the procedures were in accordance with the local and national ethical standards.
Generation XXI is a birth cohort that recruited women in all public maternity units from Porto, Portugal between April 2005 and August 2006. A total of 8647 children and 8495 mothers were enrolled at baseline. Just before recruitment, these hospitals were responsible for 91.6% of all deliveries in the catchment area. Of the invited mothers, 91.4% agreed to participate.14 and 15
Birth data were retrieved from medical records by trained researchers. Intermediate follow-up assessments were conducted in subsamples at 6 and 15 months, and weight and height measured during medical appointments were retrieved from the child's health records. At 4 years of age, 86% of all children were re-evaluated (70% by face-to-face interviews), including measured weight and height. At different ages, the child's eating behaviors were assessed based on a set of closed questions, answered by the main caregiver (usually the mother).
Subsamples were recruited at 6 and 15 months; for these analyses 980 children had complete data at 6 months and 577 at 15 months. At 48 months, 3802 had complete data for analysis.