This intergenerational link between age at menarche and infancy weight gain might be explained by genetic factors transmitted to the offspring from the mother. Both age at menarche and infancy growth rates show high heritability in studies comparing monozygous with dizygous twins [9,22,28]. Specific genes for either trait have yet to be identified, but our findings would support a common genetic pathway associated with both infancy growth and the tempo of childhood growth and puberty. Potential candidates are genes that regulate early appetite and satiety [29]. Genetic factors that influence sex hormone activity might also regulate both puberty and infant growth, as there is a mini-activation of central and peripheral sex hormones during infancy [30,31]. We have no reliable information on father's pubertal development as, in contrast to menarche in females, there are few robust self-reportable markers of puberty in males. Mother's menarche had a similar influence on her sons and daughters, and it is possible that rapid puberty in fathers might also in turn influence offspring growth.
