WHO GROWTH CHARTS FOR CANADA (Redesigned 2014)

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WHO GROWTH CHARTS FOR CANADA (Redesigned 2014)

Transcript Of WHO GROWTH CHARTS FOR CANADA (Redesigned 2014)

A Health Professional’s Guide for using the
WHO GROWTH CHARTS FOR CANADA (Redesigned 2014)
This Guide introduces the WHO Growth Charts for Canada which were first released in 2010 and redesigned in 2014 to address some primary design issues. It provides some key features of the charts and illustrates how to perform accurate anthropometric measurements in children.
Growth monitoring and promotion of optimal nutrition are essential components of health care for all children. Monitoring a child’s growth helps to confirm a child’s healthy growth and development or identify early a potential nutritional or health problem. The consequences of undernutrition during the early years include compromised immunity, cognitive problems1 and stunted growth. Over-nutrition may predispose to conditions such as obesity, diabetes and metabolic syndrome later in life2, 3. When potential problems are identified early, health professionals and parents can work together to initiate action before the child’s nutritional status or health are seriously compromised.
Activities linked to growth monitoring and promotion at the individual level4:
1. accurately measuring weight, length or height, and head circumference 2. precisely plotting measurements on the appropriate, validated growth chart 3. correctly interpreting the child’s pattern of growth 4. discussing the child’s growth pattern with the parent(s)/caregiver and agreeing on
subsequent action when required.
Regular assessment of growth should occur at well-health visits. Suggested monitoring intervals after birth are within one to two weeks of birth, at one, two, four, six, nine, 12, 18 and 24 months5, then once per year for children over 2 years and for adolescents5. Growth assessment should also occur at acute care visits5, keeping in mind that illnesses may affect weight.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)

Dietitians of Canada, Canadian Paediatric Society, The College of Family Physicians of Canada, Community Health Nurses of Canada and, in 2014, the Canadian Pediatric Endocrine Group recommend the adoption of the World Health Organization [WHO] Growth Charts6,7 in Canada8.
 The 2006 WHO Child Growth Standards for birth to five years are recommended because they are based on children raised according to current Canadian and international health and nutrition recommendations among communities where economics were likely to support appropriate growth. Breastfed infants were used as the normative model for growth and development. These charts illustrate the way healthy children should grow and are considered to be the gold standard for assessing the growth of young children.
 The WHO Reference 2007 growth charts are recommended for monitoring the growth of children and adolescents between the ages of 5 to 19 years because they have been updated to address the obesity epidemic and are therefore considered to be closer to growth standards.
What are some of the features of the WHO Growth Charts for Canada?
The WHO 2006 Child Growth Standard Charts:
 are based on a breastfed population, whereas only 50% of infants sampled for the Center for Disease Control (CDC) growth charts were breastfed at all
 generally reflect a lighter, longer/taller sample  can be used for multi-ethnic populations in Canada, as the data set is international,
representing the growth of children in six different countries (Brazil, Ghana, India, Norway, Oman, USA) for whom minimal differences in the rate of linear growth were noted6  emphasize the use of BMI-for-age as the index of weight relative to height starting at two years of age, rather than weight-for-height or percent ideal body weight  show a close match of measurements at five years of age between the Growth Standards and Growth References9.
The WHO Growth Reference 2007 Charts:
 take into account the obesity epidemic by including data that reflect healthy growth  BMI-for-age values suggestive of overweight (85th to 97th percentile) and obesity
(>97th percentile) match almost perfectly with respective adult cut-offs for overweight and obesity at 19 years of age.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)

Selecting the appropriate growth charts for the healthy term infant

WHO Growth Charts for Canada are available to download from www.whogrowthcharts.ca.

Selecting the appropriate growth charts will depend on the work setting. Table 1 is a sampling of growth charts suggested for a primary health care setting, including public health/community as well as primary care/physician’s office.

Table 1: Growth Charts for the Primary Health Care Setting

Birth-24 Months*

2-19 Years*

Length-for-age and Weight-for-age

Height-for-age and Weight-for-age

Head circumference and Weight-for-length

Body Mass Index (BMI) -for-age

* The Growth Charts in Table 1 have been adapted for Canada with permission from the World Health Organization.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)
Two versions of the WHO Growth Charts for Canada are available with alternative percentile choices:
Set 1: 3rd, 15th, 50th, 85th, 97th and the 99.9th centile for Birth-24 months, Weight-for-length; and 2-19 years, BMI-for-age (as shown in Table 1).
Set 2: 3rd, 10th, 25th, 50th, 75th, 90th, 97th (substituting 85th for 90th centile and including the 99.9th centile for Birth to 24 months, Weight-for-length; and 2-19 years, BMI-for-age).
Selecting the appropriate growth charts for preterm infants (<37 weeks) and children with special health care needs
The WHO Growth Standards did not include data on premature infants or very low birth weight infants (<1500 g); growth of these infants differs from infants born at an appropriate age or size, such that they appear not to catch up during early childhood10.
 The growth of preterm infants (<37 weeks) after discharge from the neonatal intensive care unit can be monitored using the WHO Child Growth Standards: Measurements should be plotted using corrected postnatal age for prematurity (i.e. postnatal age in weeks – [40 weeks – gestational age in weeks]) until 24 or 36 months of age11.  For example, at 12 weeks postnatal age, an infant born at 30 weeks gestational age would be 12 – [40-30] or 2 weeks corrected postnatal age. Alternate charts to assess growth of preterm and low birth weight infants in the neonatal intensive care unit or early post-discharge setting include:  Fenton’s12 Preterm growth chart for tracking growth from 22 weeks gestational age to 10 weeks post term.
 Children with intellectual, developmental, genetic or other disorders often have growth patterns that are different from healthy children. Their growth can also be monitored on the WHO Growth Charts alone, or in conjunction with specific growth curves that exist for some of these disorders13, 14, 15, 16.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)

How are measurements interpreted?
Growth measurements have little meaning until they are accurately plotted on the growth chart. The curves on the growth chart represent selected percentiles of the measurements of large numbers of children in the reference population that were studied to develop that growth chart. These percentile curves can be used to identify the child’s growth relative to other children of similar age and sex. For example, if a child’s weight is on the 85th percentile, it means that 85 of 100 children (85%) weigh less and 15 (15%) weigh more.

How should growth be assessed?
 One-time measurements, taken and plotted accurately on a growth chart, reflect a child’s size and may be used to screen children for nutritional risk using the cut-off percentiles and z-scores shown in Table 2. However, they do not provide adequate information to assess a child’s growth. A series of weight and length/height measurements over time are more informative and reflect a child’s growth pattern.
 In most children, serial weight-for-length, BMI, length/height, and weight measurements follow consistently along a percentile curve.
 It can be normal for children to change one to two percentile curves for both weight and length during the first two to three years of life17. The 50th percentile, or “average”, is not the goal for each child, as most children have the genetic potential to be taller or shorter, and heavier or lighter, than average. More importantly children’s weight should be proportional to their length/height – proportionality is evaluated by considering the child’s weight-for length or BMI. Proportionality is generally defined at being within the 3rd to 85th percentiles (within -2 to +1 z-scores).
 With the exception of the first two to three years of life when crossing percentile curves may be normal, and again in puberty, when the age of pubertal onset is variable, a sharp incline or decline in growth, or a growth line that remains flat, is potentially a sign of growth disturbance.
Serial measurements showing unexpected movement downwards on the curves from a previously established rate of growth could be a sign of failure-to-thrive (FTT)18, 19, 20, 21. Although crossing two centile curves has been used historically to identify growth that needs further examining, this method has not been validated as a method of identifying growth problems20 and could lead to delayed investigation of abnormal growth. Changes in height/weight-for-length/BMI percentiles should be assessed before crossing two percentile lines, particularly in children and adolescents.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)
Unexpected movement upwards on the weight-for-length or BMI curves may be a sign of development of overweight or obesity. Consider the following factors when evaluating growth that does not follow a healthy pattern for all children: parental height, nutritional intake, and presence of chronic illness or special health care needs (i.e. Down’s Syndrome, Cerebral Palsy etc), and for infants also consider gestational age, birth weight, and type of feeding (breast or formula).
Using Body Mass Index-for-Age
 BMI is defined as weight in kilograms divided by height in meters squared: BMI= Wt (kg)  (Ht (m)2).
 BMI correlates with body fat; pediatric BMI has been linked to future obesity and adverse health outcomes22. BMI decreases in later infancy and remains relatively stable from ages 2 to 5 years then increases through childhood and adolescence. The point of maximal leanness or minimal BMI has been called the adiposity or BMI rebound and is reflected in the BMI-for-age charts23. Early adiposity rebound before the age of 5.5 years is associated with an increased risk for obesity later in life24, 25.
 Unlike adults, age-related increases in BMI are associated with increases in both fat mass and fat free mass26; the extent to which each component contributes to changes in BMI depends on age, sex and pubertal maturation of the child27. Other factors such as comorbidities, family history, ethnic background, level of physical activity, frame size and clinical judgement should also be considered before determining growth status based on Table 2.
 BMI-for-age is the recommended nutritional indicator for screening children two years and older to identify individuals who are potentially wasted, overweight or obese.
 There is a lack of convincing evidence that BMI-for-age is better than weight-for-length at assessing adequacy of feeding, and under- and overweight in infants and toddlers under two years of age.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)
How will growth of the breastfed vs. non-breastfed baby differ when plotted on the WHO Growth Charts compared to the CDC Growth Charts?
Breastfed infants tend to grow more quickly than non-breastfed infants in the first six months and tend to grow more slowly in the second six months of life28. Since the WHO Child Growth Standards charts have been constructed based on the growth of infants that have been primarily breastfed, the breastfed infant will no longer look as though they are growing too rapidly during the first six months nor will they look as though they are failing to grow sufficiently from 6 to 12 months, compared to the CDC charts.
 Overall the WHO Growth Charts will result in higher rates of children classified as underweight or wasted/thin in the first six months of life and higher rates of children classified as stunted, overweight and obese after that time, compared to the CDC charts given the differences in feeding method and selection of healthy non-disadvantaged children29. Assessing the pattern of weight, linear growth and weight relative to length and whether the infant is breast or non-breastfed is necessary before suggesting changes in feeding.
Recommended cut-off points and terminology
Cut-off points for anthropometric measurements are intended to provide guidance for further assessment, referral or intervention. They should not be used as diagnostic criteria. Longitudinal patterns of growth should always be considered when applying cut-offs. Cut-off criteria are separated into birth to two years, two to five years, and 5 to 19 years. The recommended cut-off criteria for determining overweight and obesity status are different for children birth to five years and 5 to 19 years of age.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)

Birth to 2 years Growth Status

Table 2: Cut-off Points

Indicator

Percentile

Underweight Severely underweight Stuntedb Severely stunted Wastedc
Severely wasted Overweighte Obesef Head Circumferenceg

Weight-for-age Weight-for-age Length-for-age Length-for-age Weight-for-length
Weight-for-length Weight-for-length Weight-for-length Head Circumference-for-age

<3rd
<0.1st
<3rd <0.1st
<3rd or <89% IBWd
<0.1st
>97th
>99.9th <3rd or >97th percentile

z-scores (approximate
values) <-2 <-3 <-2 <-3 <-2
<-3 >2 >3 <-2 or >2

Two to 19 years
Growth Status
Underweight Severely underweight Stuntedb Severely stunted Wastedc Severely wasted Overweighte Obesef Severely obese

Indicator
Weight-for agea Weight-for agea Height-for-age Height-for-age
BMI-for-age BMI-for-age BMI-for-age BMI-for-age BMI-for-age

2-5 years

Percentile

z-scores (approx.)

<3rd

<-2

<0.1st

<-3

<3rd

<-2

<0.1st

<-3

<3rd

<-2

<0.1st

<-3

>97th

>2

>99.9th

>3

N/Ah

N/Ah

5-19 years

Percentile

z-scores (approx.)

<3rd

<-2

<0.1st

<-3

<3rd

<-2

<0.1st

<-3

<3rd

<-2

<0.1st

<-3

>85th

>1

>97th

>2

>99.9th

>3

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)

a Weight-for-age - Use BMI-for-age instead. Weight-for-age alone is not recommended as a nutritional parameter for any age, and especially beyond 10 years of age because of the wide variability in age at onset of puberty and its associated changes in body composition. When weight-for-age alone is used to screen for over nutrition, pubertal children may appear as having excess weight by weight-for-age when in fact they are just tall; at the other extreme, overweight children that are short or stunted would appear to be normal. The WHO recommends that weight continue to be measured for children beyond 10 years of age, for the purpose of calculating, plotting and monitoring BMI-forage11. Similarly, BMI-for-age should also be interpreted in the context of height as a child who is declining for both height and weight centiles may have a preserved BMI.
b Stunted - The infant or child may be short because parents are short (3% of normal children are expected to have heights less than the 3rd percentile) or they may be stunted because of long-term malnutrition, delayed maturation, chronic illness or a genetic disorder/syndrome or abnormal prenatal environment.
c Wasted - May be normal as 3% will be expected to have weights-for-age and BMI less than the 3rd percentile, or it may be indicative of recent malnutrition, dehydration or a genetic disorder. Traditional measures of underweight (weight-for-age, weight-for-length or % IBW) continue to be recommended for children under 2 years of age until validity of using BMI–for-age in this age group has been demonstrated.
d % IBW - Percent ideal body weight: plot length or height on growth chart to identify length-for-age percentile. Locate ideal body weight as the weight at the same percentile as the length, for the same age and gender. Calculate % IBW= actual weightideal body weight x 100.
e Overweight - Further evaluation necessary. Look for co-morbidities and possible causes. The cut-offs recommended for the younger children (birth to 5 years) are more cautious to avoid the risk of health professionals or parents putting young children on diets. Some children in this category are not overweight - weight-for-length and BMI cut-offs do not take body composition and high muscle mass into account. The cut-offs recommended for the older children (5 to 19 years) coincide at 19 years old with the adult cut-off for overweight (ie, BMI of 25 kg/m2).
f Obese – Usually denotes excess body fat and reflects the associated serious health risks The cut-offs recommended for the younger children (birth to 5 years) are more cautious to avoid the risk of health professionals or parents putting young children diets. The cut-offs recommended for the older children (5 to 19 years) coincide at 19 years old with the adult cut-off for obesity (ie, BMI of 30 kg/m2).
g Head Circumference - Reflects brain size and is used for screening for potential health, nutrition or developmental problems amongst infants from birth to 2 years old.
h N/A - Not applicable for this age group.

Accurate weighing and measuring
Accurate, reliable measurements are fundamental to growth monitoring and to making sound clinical judgments on appropriateness of a child’s pattern of growth.

Accurate measurements have three components:
 A standardized measurement technique  High quality equipment which is regularly calibrated and accurate and  Trained measurers who are consistent and precise in their technique24,30.

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A Health Professional’s Guide for using the WHO Growth Charts for Canada (Redesigned 2014)

Accurate measurement equipment and techniques
Weighing infants31:
 The infant should be weighed nude on a calibrated beam or electronic scale  The scale should be accurate and reliable with a maximum weight of 20 kg in 1 or 10 g
increments and easily “zeroed” and recently calibrated. The “average weight” feature is desirable on an electronic scale to accommodate those infants who do not remain still during the weight taking.

Measuring infant length31:

 Use calibrated length board with fixed headpiece and movable foot piece which is perpendicular to the surface of the table

 Two trained people are needed to get an accurate measurement

 Measure infant without shoes and wearing light underclothing or diaper

 The infant should be placed on his/her back in the centre of the board lying flat against the surface. Eyes should be looking up. Both legs should be fully extended and toes should be pointing upward with feet flat against the foot piece

Illustration © Nardella, M, Campo, L, Ogata, B, eds. Nutrition Interventions for Children with Special Health Care Needs, Olympia, WA, State Department of Health, 200133. Used with permission.

 Measure length to nearest 0.1 cm.

Measuring head circumference31:

 Position the tape just above the eyebrow, above the ears and around the biggest part on the back of the head
 Use a clean, flexible, non-stretchable tape  Measure to nearest 0.1 cm.

Illustration © Nardella, M, Campo, L, Ogata, B, eds. Nutrition Interventions for Children with Special Health Care Needs, Olympia, WA, State Department of Health, 200133. Used with permission.

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