figure 2-7 Argentine standard for weight, height, and head circumference from 26 to 92 weeks of postconceptional age. (Source: Lejarraga H, Fustiñana C. Estandares de peso, longitud corporal y perímetro cefálico desde las 26 hasta las 92 semanas de edad postmenstrual. Arch Argent Ped. 1986;84:210-214.)
In clinical pediatrics, the third centile is commonly used. If this limit is chosen, then bear in mind that 3% of normal children would fall below the third centile line. Many of these children, for social or psychological reasons, may go to the doctor complaining of short stature. Hence, the majority of children complaining of short stature will belong to this group of entirely normal individuals.
To answer the second question, we need at least two measurements separated by an appropriate period of time, in order to calculate the growth velocity during the period between measurements. In Chapter 16, the way growth velocity is to be calculated and evaluated on velocity charts is explained in detail. Velocity charts tell us whether the child is growing too fast, too slow, or at a normal velocity. Growth velocity can be indirectly estimated on distance charts. Let us suppose we have a patient measuring 104.0 cm at the age of 4.5 years, falling on the 35 th centile of
Figure 2-6. To determine his growth velocity, we measure him a second time at the age of 5.2 years, obtaining a height of 109.0 cm. If the slope of the growth curve created by joining both points with a line is parallel to the centile lines (curve a, Figure 2-6), we can assume that growth velocity is normal. On the other hand, if the slope of the distance curve falls away from the centile lines, as in curve b, then we must say that the child is growing too slowly. This condition should be specified as growth retardation, growth delay, or abnormally slow growth.
In young infants, with whom we cannot wait a long period of time to evaluate growth velocity in height or we have doubts on the slope of the weight curve in the first months of life, it has been very useful in our growth clinic to evaluate velocity in terms of daily weight gain in grams/day. For example, if a 3-month-old infant is seen in the clinic on January 16 weighing 6700 g, and she comes for the second time on February 24 (39 days later) weighing 6950 g, then her growth velocity (GV = the change in distance divided by the change in time) is GV = (6950 g - 6700 g)/39 = 6.4 g/day, which in Figure 2-8 falls well below the 10th centile line of normal values for weight velocity.18 This method also allows for children attending the clinic at very irregular intervals.
As we can see in Figure 2-6, size attained and growth velocity are both rather independent concepts. Some cases show normal size (example b) growing at a slow velocity (from x to y), other cases show short stature (example c) growing at a normal rate, and in still others, both size attained and velocity are abnormally low (from w to z). Size attained can be considered the cross section of a continuous growth process taken place from birth (or better, from conception) up to the moment in which the child was measured. It is the result of the algebraic sum of all growth experienced before the measurement was taken. Growth velocity, in turn, reflects the process occurring exclusively during the period in which the child was measured.
Gain g/day BOYS
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