Canalisation in human growth: a widely accepted concept reconsidered

According to the concept of canalisation, infants and children stay within one or two growth channels, and therefore, any crossing of height centiles always warrants further evaluation. In view of evidence against this concep t we re-investigated the variability of individual growth in the First Zuri ch Longitudinal Growth Study. The investigation is based on height measurem ents of 232 children (112 females, 120 males) measured at annual intervals during childhood and half-yearly during adolescence. Height data were trans formed into height standard deviation scores (SDS) and canalisation defined by the width of an individual's growth channel, i.e., by the differences b etween maximum and minimum height SDS, in the individual series of measurem ents. Many subjects of the First Zurich Longitudinal Growth Study crossed n umerous centiles with patterns that often seemed to show characteristic fea tures. For approximately two thirds of the subjects, the SDS channel during the whole growth process covers more than one SDS. In childhood, between t he age of two and age of minimal height velocity, only about one fourth of the subjects have an SDS channel below 0.5, indicating acceptable canalisat ion. During childhood, growth in boys appeared slightly more canalised than in girls (P = 0.02). Conclusion The present investigation does not support the concept of strict canalisation of individual growth. We suggest to consider crossing of cent iles a normal event in child development, though in a clinical setting cros sing centiles should still be taken seriously, at least at first until a me dical cause for this has been excluded.