Hvidt JJ, Brix N, Ernst A, et al. - In this population-based cohort study, researchers intended to determine if there is an association between the duration of breast feeding and pubertal timing in boys and girls. The sample consisted of 13,511 boys and girls from the Puberty Cohort nested within the Danish National Birth Cohort. Through questionnaires, the children provided half-yearly, self-reported information on pubertal development (Tanner stages, age at menarche, first ejaculation, voice break, axillary hair growth, and acne). When the children were 6 months old, their mothers gave them information on breast feeding. According to results, exclusive breast feeding for a shorter period of time was associated with earlier pubertal development in boys but not in girls.