Standards from birth to maturity for height, weight, height velocity, and weight velocity: British children, 1965 part II

Abstract

Conventional centile standards of height and weight attained at each age from birth to maturity, appropriate for British children in 1965, are given. These differ from previous standards because children have become larger. They answer the question, 'Is this child's size within normal limits ?' in a circumstance in which the child has been examined once only. In the same chart a new type of standard is also given, which is more appropriate for judging whether a whole segment of the child's growth curve has been normal. Conventional charts give an erroneous impression of the course of growth at adolescence if used to follow a single child longitudinally, as in clinical work. This is due to the 'phase-difference' effect which is discussed and illustrated. In conventional charts a late-maturing child, for example, departs at adolescence from the height centile he has previously been following, reaches a lower centile, and later regains his original centile. In the new 'individual-type' charts this effect is obviated. Centile standards for the velocity of growth in height and weight from birth to maturity are presented. They relate to increments calculated over the period of a whole year, since over shorter periods the variability of growth rate is higher due to seasonal alterations. In addition to these standards, at adolescence the velocity equivalent of the new type of height-attained standard is given. This shows the curve of velocity where phase differences are eliminated. The use of skeletal age as an alternative time base to chronological age over this period is discussed. To obtain the curves for the new 'individual-type' standards it is necessary to use longitudinal records extending over adolescence. The records of the Harpenden Growth Study were used for this purpose. In 49 boys and 41 girls measured every three months throughout adolescence, curves were fitted graphically to height and weight measurements and velocities thus derived. The average 'instanttaneous' peak height velocity was 10.3 ± 0.22 cm./ yr. in boys and 9.0 ± 0.16 cm./yr. in girls. There was a correlation of -0.47 and -0.40 in boys and girls between peak height velocity and the age at which it was reached. No such correlation existed for peak weight velocity. The peak weight velocity was 9.8 ± 0.30 kg./yr. for boys and 8.8 ± 0.25 kg./ yr. for girls. The correlations between peak height velocity and peak weight velocity were only 0.29 and 0.18 in boys and girls, but the correlations between age at reaching peak height velocity and at reaching peak weight velocity were 0.93 and 0.80. Curves of distance and velocity for the typical or 50th centile boy and girl are contrasted. In both height and weight boys are growing faster than girls at birth, but are also decelerating more, so that by 7 or 8 months they are growing more slowly than girls. Examples are given of the clinical use of the new standards, in a healthy child followed from 3 to 16, and in a dwarf treated with human growth hormone. Height and weight are routinely plotted against both chronological and skeletal age. The way in which plots of 'distance' and velocity of growth complement each other is discussed, and the extreme methodological difficulty of providing a valid quantitative answer to the seemingly simple question 'Has this treatment significantly altered the child's rate of growth?' It is shown how the new charts can at least be used to give an approximate answer to this question.