Tag Archives: growth charts

Outgrowing the growth charts

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Unfortunately, there is a need for extreme growth charts (Pediatrics 2012; 130: 1136-40).

The authors of this study designed growth charts for morbidly obese children.  The reason for these charts is that there are many pediatric patients who cannot be plotted using the CDC  growth chart which has a maximum BMI of 36 kg per meter-squared.  The CDC charts are based on a preobesity epidemic population data set (1963-94) and has sparse data for those above the 97th percentile.  The manuscript describes how these initial charts were derived.

These new growth charts calculate the BMI as a percentile of the 95th percentile.  For example, multiplying the BMI 95th % by 1.2 would yield a result of 120% of the 95th%.  The authors calculated 1.1 through 1.9 multiples of the 95% for all ages between 2 and 20 years.  On their curve, a BMI as high as 64 kg per meter-squared can be plotted.  This allows easier visual tracking of a patient’s progress.

Drawbacks:

  • Difficult to explain to parents due to confusing phraseology –use of two percentages
  • Many of the patients are now on the growth curve and could appear to be graphically normal despite being morbidly obese

The authors note that their growth charts were incorporated into their electronic medical record (Epic software).

Related blog entry:

Better growth charts for preterm children

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A community-based cohort study from the Netherlands involving 1690 preterm infants (25-36 weeks) and a random sample of 634 full term infants provides a more precise tool for monitoring growth over the first four years of life (J Pediatr 2012; 161: 460-5).

Key findings:

  • The lower the gestational age, the lower the median value for both weight and height.  A quick glance at their tables indicate that infants born at 25 weeks gestation remained on average about 2 kg and 4 cm smaller than full term infants.  Infants born at 32 weeks gestation were on average about 1 kg and 2 cm smaller through the study period.
  • The absolute differences in weight and height were nearly constant, indicating that there was a lack of ‘catch-up’ growth.  At the same time, a child ‘following his own curve’ parallel to growth curve is likely a normal pattern
  • Head circumference at the end of the first year was similar between preterm and term infants
  • Greater variability was noted in boys

While this study did not adjust for maternal height, it is known that short maternal height does correlate with increased likelihood of short offspring.  This is partly mediated by having a small for gestational age birth.  Other limitations of the study included that the cohort was >90% Caucasian, and there was no adjustment for multiple births.

Useful links/references:

  • Growth Charts – Homepage -CDC growth charts
  • Pediatrics 2011; 128: e1187-94.  Growth and predictors of growth restraint in moderately preterm-born children.
  • Pediatrics 2003; 112: e30-8.  Growth of preterm infants during 1st 20 years.