2011 ). Such an interpretation and translation to practice raises both practical and
ethical issues. As more than 60% of infants display these types of“percentile
crossing”patterns in thefirst year of life (Mei et al. 2004 ), the specificity of a risk
has yet to be established. Moreover, it is not at all clear what sort of nutritional
alterations are appropriate for growing infants (Frongillo and Lampl 2011 ).
Biomarkers of Growth
A shortcoming of the reliance on growth charts as the model of human growth is
that the graphical images have come to be accepted as the definition of“normal”
growth. Rather than merely representing a size reference, the graphs themselves
have incorrectly come to stand for the biology of growth, with the expectation that
individual children grow continuously as portrayed by the percentile curves, with
biological processes unfolding analogously to an individual marching up one or
another of the growth curve paths, following one of the percentile trajectories with
little deviation (Fig.4.1). In reality, growth charts are not designed to characterize
the process by which individuals actually grow (Lampl and Thompson 2007 ).
Growing is an individual-level biological process in which length/height occurs
at endochondral growth plates within 24 h at sporadic intervals. While infrequently
Fig. 4.3 Saltation and stasis growth patterns are unique to individuals. Some children grow
frequently and some more seldom; some grow at robust amplitudes and others experience more
modest gains at each length growth saltation. These pulsatile growth patterns do not follow the
growth curve percentile trajectories. This is because the growth charts represent summaries of
group statistics, and the curvature in the graphs does not reflect actual growth rates of individuals.
As 60% of infants regularly cross percentile lines during development, the medical utility of such
crossings for predicting“poor”health is unclear
4 The Lived Experience of Growing 53