WHO Child Growth Standards: Evolution, Concepts and Global Overview

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WHO Child Growth Standards Evolution, Concepts
and Global Overview

• Dr. Mercedes de OnisDepartment of Nutrition
• World Health Organization
• Geneva, Switzerland

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WHO Child Growth Standards

• Why?

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Rationale for the development of the WHO child
growth standards

• The recommended NCHS/WHO international
  reference
• is inappropriate for assessing nutritional
  status
• Individual infants
• interferes with sound nutritional management
  of breastfed infants, increasing their risk of
  morbidity and mortality
• Populations
• provides inaccurate estimates of
  undernutrition and overweight

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Milestones in the development of theWHO child
growth standards

• 1991-1993 WHO Working Group on Infant Growth
• Comprehensive review shows growth patterns of
  healthy breastfed infants differ from the current
  NCHS/WHO international reference
• A new growth reference is needed to improve
  infant health management
• The reference population should reflect health
  recommendations in view of the frequent use of
  references as standards

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Mean Z-scores of healthy breastfed infants
relative to the NCHS/WHO reference
Source An Evaluation of Infant Growth, WHO, 1994
Source An Evaluation of Infant Growth, WHO, 1994
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Rationale for the development of the WHO child
growth standards
Upward skewness of reference population
childhood obesity



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Milestones in the development of the WHO child
growth standards

• 1993 WHO Expert Committee
• Recommends development of a new international
  growth reference
• Based on an international sample of healthy
  infants
• 1994 WHA resolution (WHA 47.5)
• Endorses need for new reference
• Requests it to be based on breastfed infants

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WHO Child Growth Standards

• How?

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A Growth Curve for the 21st Century
The WHO Multicentre Growth Reference Study
Department of Nutrition World Health
Organization Geneva, Switzerland
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Approaches for developing growth references

• Descriptive approach
• defines growth on the basis of representative
  samples of healthy groups, i.e., without
  identifiable disease
• Prescriptive approach
• defines growth on the basis of health and feeding
  practices known to promote optimal growth and
  selects the sample accordingly

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WHO Growth Reference StudyPrescriptive Approach

• Optimal Nutrition
• Breastfed infants
• Appropriate complementary feeding
• Optimal Environment
• No microbiological contamination
• No smoking
• Optimal Health Care
• Immunization
• Pediatric routines

Optimal Growth
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Eligibility criteria of study population

• SES that does not constrain growth
• Altitude lt 1,500m
• Low mobility target population
• Minimum 20 of mothers follow feeding
  recommendations
• Existing breastfeeding support system
• Presence of collaborative institutions

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Eligibility criteria of individuals

• No health, environmental or economic constraints
  on growth
• Mother willing to follow feeding recommendations
• Term birth
• Single birth
• Lack of significant perinatal morbidity
• No smoking mothers (before and after delivery)

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Parental education (y)
January 2004
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MGRS study design
Longitudinal (0-24 months)
year 1
year 2
year 3
Cross-sectional (18-71 mo)
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Time schedule child anthropometry in longitudinal
study (21 visits)
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Motor development

• Six universal motor development milestones
  assessed between 4 and ? 18 months of age.

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WHO Multicentre Growth Reference StudyMotor
Development Assessment
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Sample size

• Total sample 8,440 children by combining
• cohorts ? 300 newborns per site
• 1,400 children aged 18 to 71 months per site
• Target of growth curves 400 both sexes

WHO Multicentre Growth Reference Study
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Compliance with feeding and smoking
recommendations
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Measurement and standardization protocols

• Rigorous scientific standards are applied to a
  complex cross-cultural field-based project.

WHO Multicentre Growth Reference Study
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Data management
Brazil
Ghana
Norway
Oman
India
USA
WHO Geneva
Steering Committee
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The WHO Multicentre Growth Reference Study
Rationale, Planning Implementation
Food and Nutrition Bulletin vol 25, no.1
(supplement) March 2004
WHO Multicentre Growth Reference Study
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WHO Child Growth Standards

• Construction
• growth
• standards
• WHO, Geneva

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Mean length from birth to 24 months for the six
MGRS sites
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Length at selected centiles for the pooled sample
and the sample following the exclusion of Norway
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Length at selected centiles for the pooled sample
and the sample following the exclusion of India
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Construction of growth curves

• The rigorous methods of data collection yielded
  very high-quality dataset
• State-of-art statistical methods applied in a
  methodical way
• Detailed examination of 30 existing methods,
  including types of distributions and smoothing
  techniques
• Selection of a software package flexible enough
  to allow comparative testing of alternative
  methods and the actual generation of the curves
• Systematic application of the selected approach
  to the data to generate models that resulted in
  the best fit
• Ongoing statistical review by external expert
  panel

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Concordance between smoothed curves and empirical
values Length-for-age, boys, 0-24 months
Source WHO Multicentre Growth Reference Study
Group. WHO Child Growth Standards
Length/height-for-age, weight-for-age,
weight-for-length, weight-for-height and body
mass index-for-age Methods and development.
Geneva World Health Organization, 2006.
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WHO Child Growth Standards

• Attained growth
• Weight-for-age
• Length/height-for-age
• Weight-for-length/height
• Body mass index-for-age
• Mid-upper arm circumference-for-age
• Triceps skinfold-for-age
• Subscapular skinfold-for-age
• Head circumference-for-age
• Growth velocity
• Weight
• Length/height
• Head circumference
• Arm circumference

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Comparison of WHO with NCHS length/height-for-age
z-scores for boys
Source WHO Multicentre Growth Reference Study
Group. WHO Child Growth Standards
Length/height-for-age, weight-for-age,
weight-for-length, weight-for-height and body
mass index-for-age Methods and development.
Geneva World Health Organization, 2006.
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Prevalence of stunting (below -2 SD
length/height-for-age) by age based on the WHO
standards and the NCHS reference in Bangladesh
Source de Onis M, Onyango AW, Borghi E, Garza C,
Yang H, for the WHO Multicentre Growth Reference
Study Group. Comparison of the WHO Child Growth
Standards and the NCHS growth reference
implications for child health programs. Public
Health Nutrition 20069942-947.
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Comparison of WHO with NCHS 1977 weight-for-age
z-scores for boys
Source WHO Multicentre Growth Reference Study
Group. WHO Child Growth Standards
Length/height-for-age, weight-for-age,
weight-for-length, weight-for-height and body
mass index-for-age Methods and development.
Geneva World Health Organization, 2006.
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Prevalence of underweight (below -2 SD
weight-for-age) by age based on the WHO standards
and the NCHS reference in Bangladesh
Source de Onis M, Onyango AW, Borghi E, Garza C,
Yang H, for the WHO Multicentre Growth Reference
Study Group. Comparison of the WHO Child Growth
Standards and the NCHS growth reference
implications for child health programs. Public
Health Nutrition 20069942-947.
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Mean weight-for-age z-scores of healthy breastfed
infants relative to the NCHS, CDC and WHO curves
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No gift is more precious
Breastfeeding

• provides perfect nutrition
• provides initial immunization
• prevents diarrhoea
• maximizes a childs physical
• and intellectual potential
• supports food security
• bonds mother and child
• helps birth spacing
• benefits maternal health
• saves money
• is environment-friendly

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WHO Child Growth Standards
The new standards will play a key role in the
prevention and early recognition of childhood
obesity
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Prevalence of overweight (above 2 SD
weight-for-length/height) by age based on the WHO
standards and the NCHS reference in the Dominican
Republic
Source de Onis M, Onyango AW, Borghi E, Garza C,
Yang H, for the WHO Multicentre Growth Reference
Study Group. Comparison of the WHO Child Growth
Standards and the NCHS growth reference
implications for child health programs. Public
Health Nutrition 20069942-947.
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WHO standards versus NCHS reference

• Important differences that vary by age group,
  sex, growth indicator, specific percentile or
  z-score curve, and the nutritional status of
  index populations.
• Differences are particularly important during
  infancy due to type of feeding and issues related
  to study design (eg, measurement interval)
• Difference in shapes of the weight-based curves
  in early infancy makes interpretation of growth
  performance strikingly different depending on
  whether the WHO standard or the NCHS reference is
  used
• Healthy breastfed infants track along the WHO
  weight-for-age mean z-score while appearing to
  falter in NCHS from 2 months onwards
  implications assessment of lactation performance
  and adequacy of infant feeding

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Field testing prior to release of standards

• Preliminary standards field tested in four
  countries Argentina, Italy, Maldives and
  Pakistan
• Compare nutritional status classification by
  WHO standards with assessments by pediatricians
• Clinical assessments matched with WHO
  standards' classification on weight and height
  (results published Jan 2007)
• Adoption of the WHO standards will harmonize
  assessment of child growth within and among
  countries

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Implementation phase

• About 100 countries use NCHS reference
• Regional consultations (AFRO, AMRO, EMRO, EURO,
  SEARO, WPRO) in 2006
• Training of trainers workshops (AMRO, EMRO, AFRO,
  SEARO, WPRO) in 2007
• Application tools
• Training materials with generic child growth
  record
• PC and PPC software for clinical and population
  uses
• Growth chart catalogue (60 charts 1st set of
  standards)
• Simplified field tables
• Expanded tables for constructing national health
  cards
• Website www.who.int/childgrowth

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Training Course on Child Growth Assessment

• Measuring techniques (weight, length/height)
• Calculating BMI
• Interpreting growth indicators
• Investigating causes of poor growth
• Counselling mothers on growth, feeding and caring
  practices

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WHO Child Growth Standards Key documents

• Food and Nutrition Bulletin 2004 25 (Suppl 1)
• Acta Paediatrica 2006 95 (Suppl 450)
• WHO Technical Report 2006
• Website www.who.int/childgrowth/en

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WHO Child Growth Standards Innovative aspects

• Prescriptive approach recognizing need for
  standards
• Breastfed infant as normative model
• International sample
• Reference data for assessing childhood obesity
• Velocity reference data
• Link between physical growth and motor
  development

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Strategy for promoting healthy growth and
development
Training on its appropriate use and
interpretation
Development of a sound international growth
standard
Clinical and Public Health Interventions
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Rationale for promoting healthy growth and
development

• Childhood morbidity
• Childhood mortality
• Childhood obesity
• Child cognitive development
• Adult-life consequences

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WHO Child Growth Standards Timeline
Growth Standards 2nd set
Growth Standards 1st set
WHA Resolution (May 1994)
Construction and testing of growth standards
WHO Expert Committee recommendation (Nov 1993)
Velocity Standards
(July 97)
(Nov 03)
WHO Multicentre Growth Reference Study
WHO Working Group on Growth Reference Protocol
WHO Working Group on Infant Growth
Field implementation
Growth Standards 1st set Length/height-for-age,
weight-for-age, weight-for-length,
weight-for-height, BMI-for-age and motor
development indicators Growth Standards 2nd
set Head circumference-for-age, arm
circumference-for-age, triceps skinfold-for-age
and subscapular skinfold-for-age
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WHO Child Growth Standards

• Child survival
• Physical growth
• Child development