restriction restriction (Figueras and Gardosi 2011 ), a diagnosis that raises concerns
about the health of the pregnancy overall and prompts clinical attention to both
mother and fetus. While a handy marker, the robustness of a 10th percentile cutoff
for diagnostic concern has been debated, and investigations of inter-ethnic out-
comes suggest a reconsideration of the utility of this one-size-fits-all diagnostic
biomarker due to variability in morbidity and mortality outcomes according to
genetic background (Kierans et al. 2008 ). At later ages, the label of“idiopathic
short stature”is often applied to children and adolescents who are more than two
standard deviations below an age- and sex-adjusted average height in the absence of
any identifiable endocrine abnormality, metabolic disruption, or other disease
(Ranke 1996 ). This category can prompt decisions to treat children with, for
example, growth hormone therapy. While these are evidence-based interventions
and the growth chart centile is the biomarker criterion, physicians do not employ
similar cutoffs for treatment. Clinical actions are taken variously for children below
the tenth,fifth, third, or evenfirst percentile, resulting in a sliding definition of
abnormal growth; this is associated with confusion not only among families, but
also within clinical and research communities (Silvers et al. 2010 ).
Further difficulties associated with percentile charts as biomarkers are based on
faulty understandings regarding the fundamental information they provide. When
traditional pediatrically acquired measures from individual children are plotted serially
on growth charts, the measurements do not necessarily lie along a single percentile
line. This is because individual children do not grow continuously and do not grow in
tandem as groups of children (Lampl and Thompson 2007 ), but instead follow their
own unique biological clock in accruing episodic increments in length. Individuals
have unique saltatory growth spurt patterns (Fig.4.3). Some children grow frequently
and some more seldom; some grow at robust amplitudes and others experience more
modest gains at each length growth saltation (Lampl et al. 1998 ). This biological
variability underlies the common observation that the smallest child at the end of
second grade can return after the summer as the tallest child in third grade, only to be
again less than the average height by the end of the subsequent school year.
Commonly, a small infant at birth may grow relatively rapidly, experiencing
more frequent and higher amplitude saltatory length increments in thefirst four to
six months of life in comparison with those observed among larger infants at birth,
as the smaller individuals “catch-up” following limitations imposed by the
intrauterine environment during late gestation (Cameron et al. 2005 ). Hence, when
plotted on the static growth chart graphical distributions, individual trajectories
often cross percentile lines. For example, the child whose data are shown in the top
of Fig.4.3is below the 50th percentile of size for his age at three months of age,
but above the 75th percentile of size for age by 1 year, having“crossed”two
percentile lines in his relative size by comparison with his peers. This normal
phenomenon has been suggested to be a harbinger of potentially inappropriate
accelerations, or insults. For example, due to worries about health risks associated
with rising rates of childhood obesity this graphic sign has recently been proposed
as a call for dietary intervention among infants when body weight or body mass
index (BMI) plots cross two centile lines in thefirst year of life (Taveras et al.
52 M. Lampl et al.