NewsNew WHO growthstandardsThis New WHO Growth Standards for infants and childrenup to 60 months of age, highlighted in <strong>Field</strong> <strong>Exchange</strong> 27, arenow available. The standards were developed using data collectedin the Multi Centre Growth Reference (MGRS) study.They describe normal child growth from birth to 5 yearsunder optimal environmental conditions and can be appliedto all children everywhere, regardless of ethnicity, socio-economicstatus and type of feeding.The new standards differ from any existing growth charts ina number of ways:• The new standards are prescriptive and describe howchildren should grow. This differs to the descriptive referencesthat have only been available until now.• Breastfeeding is the biological norm and the breastfedinfant is established as the normative growth model. Theprevious growth reference was based on the growth ofartificially fed children.• The pooled sample from the six participating countrieshas allowed the development of a truly internationalstandard (in contrast to the previous international referencethat was based on children from a single country).Child populations grow similarly across the world’smajor regions when their needs for health and care aremet.• These standards include new growth indicators beyondheight and weight, such as skinfold thickness.• The study’s longitudinal nature allows the developmentof growth velocity standards. This should enable the earlyidentification of children in the process of becomingunder or over nourished, rather than waiting for childrento cross a growth threshold.• Six key motor development milestones are included thatprovide a link between physical growth and motor development.The WHO continues to recommend the use of theNCHS/WHO international growth reference for childrenolder than 5 years. The new standards do not affect anthropometricmeasures, indicators, cut-offs, etc, for adolescents,adults, pregnant adults, and the elderly.The new growth standards will have implications foremergency nutrition programming, especially for screening,prevalence estimation and monitoring/evaluation.A paperby WHO comparing growth patterns and estimates of malnutritionbased on the WHO Child Growth Standards and theNCHS/WHO reference is currently in press 1 . This analysishighlights important differences between the WHO standardsand the NCHS reference that vary by age group,growth indicator, specific percentile or z-score curve, and thenutritional status of index populations. Particularly relevantfor emergency contexts, the analysis identifies increasedprevalence of wasting and severe wasting using the newgrowth standards, in infancy (2.5 – 3.5 times the estimatesbased on the NCHS references) and also throughout childhood(1.5 to 2 times the NCHS based estimate). The operationalimplications for emergency nutrition programming arenot explored in this paper but are highlighted in a detailedletter submitted to <strong>Field</strong> <strong>Exchange</strong> (see this page).The standards and associated software are available on theWHO website www.who.int/childgrowth.Training and sensitisation will be taking place in variousparts of the world during this year.For further information, contact: Dr Mercedes de Onis,World Health Organization, Department of <strong>Nutrition</strong>, 1211Geneva 27 Switzerland. Telephone: 41-22-791 3320.Fax: 41-22-791 4156. E-mail: deonism@who.int1de Onis M, Onyango A, Borghi E, Garza C, and Yang H. Comparison of theWHO Child Growth Standards and the NCHS growth reference: implications forchild health programmes. Public Health <strong>Nutrition</strong>, 2006 (in press).LettersThis new 2006 WHO Growth standards:What will they mean for emergencynutrition programmes?Dear EditorWhilst welcoming the principleswhich have driven the developmentof the new 2006 WHO growth standards(see news piece this page), wewish to draw attention to importantpractical implications for emergencynutrition programmes. We think it isimportant that these are exploredand discussed in detail before thenew standards are implemented inoperational settings.The need for new growth standardsAn internationally valid, ‘gold standard’range against which childgrowth can be assessed has longbeen needed. There are several reasonswhy the previous NCHS(National Centre for HealthStatistics)/ WHO Reference data fellshort of this ideal:i) It was constructed on a cohortof North American children,from a single community and asingle ethnic group of Europeanancestry.ii) Data was gathered from 1929-1975, a long period duringwhich nutrition varied greatly.The main issue of concern wasthat infants were pre-dominantlybottle-fed rather than breastfed,as is considered ideal today.iii) Statistical methods haveadvancedsignificantly since the originalNCHS/WHO growth curveswere constructed in the 1970’s.Applying better statistical techniquesto the same dataset waswhat led to the CDC 2000growth references.Age/Monthsiv) Increasing numbers of studiesin both developed and developingcountry settings found thatapparently healthy, breastfedchildren were being labelled asabnormal according to theNCHS/WHO References.MGRS (Multi-centre GrowthReference Study)The MGRS 1 ran from 1997-2003 andwas explicitly designed to generatea growth standard to show howchildren should grow, rather thanjust a reference that allows comparison.Following extensive screeningto select only those children free ofhealth or environmental (socio-economic/nutritional)constraints togrowth, a total of 8,440 childrenwere observed at six internationalsites (Brazil, Ghana, India, Oman,Norway, USA). The study had twocomponents: longitudinal work followedchildren from birth to 24months; a cross-sectional studyobserved children from 18-71months. State-of-the-art statisticaltechniques were chosen to constructgrowth curves from this data. Keyoutcomes from the MGRS are:i) The strongest evidence yet thata single international childgrowth standard is valid. Freeof environmental and nutritionalconstraints, children of very differentethnic groups all grew thesame: only 3% of length variancewas due to inter-site differences.ii) New z-score and percentile references charts/tables for weightforage,length/height-for-age,and weight-for-length/height.iii) Additional standards not presentin NCHS/WHO Reference:Body Mass Index (BMI); Midupper arm circumference1www.who.int/childgrowth/en/Figure 1 – Comparison of weight for age percentiles for boys aged 0-36 months15
(MUAC); skin-fold thickness;and motor developmental milestones.iv) A devoted website with extensiveliterature relating to MGRS and thenew standards.v) Free downloadable software whichmay, in the future, enable both individualand population anthropometricstatus to be calculated using eitherNCHS/WHO Reference or WHOStandard data.Differences between the old and newgrowth curvesThere are important differences betweenthe old references and the new standards.There is however no easy or consistentway of transforming anthropometricmeasures between the two: the growthlines do not run in parallel with simpleshifts up or down. Factors affecting themagnitude and direction of differencesbetween old and new cut-offs include: achild’s age; a child’s length/height; whichmeasure (i.e. WHZ; WAZ or HAZ) is beingconsidered; whether the child under considerationis above or below median; andwhether the z-score or % of median isbeing considered. As an example, shownbelow are the weight-for-age percentilelines (P) for boys between 0 and 36months. The curves cross, sometimes morethan once, illustrating that the magnitudeand direction of the difference between theNCHS/WHO Reference and the WHOStandards is dependent on the age of thechildren and his location on the distribution.In short, the net effect of the new standardson the measurement and diagnosisof growth and malnutrition is complex!Implications for emergency nutritionassessments and feeding programmes1. Comparability and interpretation ofnutrition dataInterpreting trends in nutritional statusand setting agreed thresholds for actionare important for emergency nutrition programmes.With the adoption of the newWHO standards the ability to easily comparethe results of current surveys withprevious data will be lost, and this willmake new data more difficult to interpret.This problem could be overcome byallowing for a period of dual-analysis ofsurvey data. If results from surveys areanalysed using both the new WHOStandards and the currently usedNCHS/WHO Reference, then sufficientdata and experience may be built up withthe new system whilst assuring ‘backwardscompatibility’. Though potentiallycomplex and confusing for non-specialistpolicy-makers, this approach would eventuallyenable trend and risk models to berecalibrated and appropriate new actionthresholds set. However, a note of cautionmust be added. Although software is availablefrom the WHO web site that can beused to analyse surveys (WHO Anthro2005), at the moment it does not deal withcases of oedema in the standard way, makingcalculation of the correct estimates ofGlobal Acute Malnutrition (GAM) andSevere Acute Malnutrition (SAM) difficult.2. Prevalence assessments using z-scoresWeight-for-length/height is a key anthropometricmeasure for emergency feeding,widely used in malnutrition prevalencesurveys to assess the need for, or effect of,a nutrition programme. It is thereforeimportant to know what are the expectedeffects of the WHO Standards on the measuredprevalence of GAM and SAM.• Effect on SAM ~ a marked increaseOverall, the new WHO standards willincrease the measured prevalence of SAMthrough increasing the value of the weightfor height
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