For example, newborns with all three disorders display a weak desire to nurse, and slower childhood growth in general. Many also show early onset of puberty, which often marks a point at which children become less dependent on their mothers' sustenance.

Conversely, babies with Beckwith-Wiedemann syndrome, in which some maternally derived genes are suppressed and paternal genes dominate, are born heavy with particularly large tongues. These individuals usually end up being tall, owing to their rapid growth both in the womb and as young children. They have a high frequency of childhood cancers.

"Clinical data from imprinting disorders suggest paternally-expressed genes promote, and maternally-expressed genes inhibit, childhood growth," Haig writes.

Haig adds that further longitudinal study of feeding and development in individuals with Silver-Russell syndrome, Prader-Willi syndrome, Temple syndrome, and Beckwith-Wiedemann syndrome is needed to more fully understand the role of genomic imprinting in such disorders.

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