WHO growth curves

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Catherine Le Nevez
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If you want to know how much children grow up in the first months, what are the most important phases and if the baby is growing well, it is advisable to calculate the percentiles, thus discovering his growth curve with respect to the parameters established byWorld Health Organization.

Let's see what the growth curves WHO and why it distinguishes between old and new.

In this article

  • WHO growth curves, what they are 
  • The new WHO growth curves
  • WHO growth curves, which are the best? 

WHO growth curves

Percentiles (or rather percentile diagrams) are the units of measurement used to establish how a child grows in weight and height. Using percentiles helps you determine if the growth rate is acceptable and, therefore, to discard problems relating to physical development.

Generally, when the pediatrician makes health assessments, he also communicates to the parents a which percentile the baby belongs. To calculate the percentiles are created particular graphics in which the percentage values ​​relating to weight, height, body mass index and head circumference of children are entered, divided according to gender and age. Thanks to these values, placed in a specific Cartesian plane, the growth curve of the child, able to offer fundamental information on his physical development. 

Therefore, the growth curve is equivalent to a graph in which the increase of auxological parameters (weight, height, body mass index and head circumference). Under normal conditions, the curve has a slope that varies according to the age group of the child.

Read also: Health balances, what they are and when to do them

The new WHO growth curves

In the years Seventy the scientists of the National Center for Health Statistics collected the parameters of various pediatric populations - belonging to various age groups - in defined time intervals and, thanks to these, growth curves for males and growth curves were created for females. 

On April 27, 2006, WHO launched its own new growth curves, at the end of a process that began in 1994, when the inadequacy of the curves of the National Center for Health Statistics (NCHS) of 1977, based on a sample of American children fed mainly with artificial milk, was recognized.

To produce the new curves, WHO conducted, between 1997 and 2003, one study on a sample of 8440 children in 6 countries: Brazil, Ghana, India, Norway, Oman and the USA. These infants had to follow very strict feeding standards (including exclusive or predominant breastfeeding for at least 4 months and the introduction of nutritionally adequate complementary foods between 4 and 6 months).

Furthermore, the children had to grow up in an environment that minimized the risk of infection, had to be fully vaccinated according to local schemes, had quick access to treatment in case of illness, and their mothers had to smoke neither during pregnancy nor after. Thus it was possible to build very precise curves, for males and females, covering weight and length / height for age, weight for length / height, and body mass index (Bmi) for age. 

Read also: Growth curves: what they are and how to read them

WHO growth curves, which are the best?

According to the Istituto Superiore di Sanità, it is not automatic that the new curves are better than the previous ones. The consequences of adopting the new growth curves will depend on how they are used. 

In fact, according to the ISS, to use the curves well it is necessary to take into consideration the following points:

  • "Keep in mind that the indicator to be used to assess growth is not the anthropometric index (weight for age, length / height for age, weight for length / height, body mass index, known as BMI or BMI, for age) in itself, measured once; nor is it the curve obtained by joining the points corresponding to successive measurements of these anthropometric indices. But it is there variation over time of the growth rate measured with these indices, that is, the variation of the slope of the curve over time.
  • It is necessary to be able to correctly interpret the variation of the slope of the curve over time. That is, to be clear that the important thing is not to know if a child is at the 3rd, 50th or 97th percentile; a 3rd or 97th percentile child with a growth rate appropriate for that percentile may not need surgery, while a 50th percentile child who increases or decreases his or her growth rate may need surgery, passing to the 40th or 60th percentile, in sufficient time to ascertain that it is not an occasional event.
  • Be able to combine the correct interpretation of the growth assessment with other indicators of the child's health status (motor and psychic development, any illnesses or conditions) and the environment in which he lives (family relationships, social and economic factors) to arrive at a diagnosis and then decide if an intervention is necessary. Not all children with stunting require feeding intervention, just as not all children with no stunting are exempt from feeding interventions. To decide whether to intervene, it is obviously necessary to have interventions of proven effectiveness ".

Indeed, as recent studies published in the UK show, parents and caregivers place more emphasis on the weight curve than other factors and weigh babies more often than recommended, even worrying about minimal fluctuations in the weight curve.

All of this would seem to suggest that it is not enough to produce better or standard curves, in place of worse or reference curves, and that perhaps it would have been more useful for parents and caregivers to be able to better use existing curves.

However - concludes the ISS, "it is good to have improved and standard curves, but this is only the first step and perhaps the easiest: it is now a question of using them well".

Read also: Calculate percentiles

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