Conceptual issues related to the construction of prescriptive standards for the evaluation of postnatal growth of preterm infants.

Monitoring and interpreting the growth of preterm infants is a major clinical task for neonatologists. The effectiveness of this process depends upon the robustness of the standard selected. Concerns have been raised regarding the nature of the charts currently being used, as well as their appropriateness for present-day neonatal care. To overcome these problems, there is a need for new prescriptive standards based on a population of preterm infants without evidence of impaired fetal growth and born to low-risk women followed up since early pregnancy for precise gestational age dating. Preterm infants contributing to the new standards should be free of congenital malformations and major clinical conditions associated with impaired postnatal growth. These infants should receive standardised, evidence-based clinical care and should follow current feeding recommendations based on exclusive/predominant breastfeeding. This strategy should provide a population that is conceptually as close as possible to the prescriptive approach used for the construction of the WHO infant and child growth standards. New international standards constructed in this way should contribute to the evidence-based care of these preterm infants.

[WHO growth standards for infants and young children]. / Les standards de croissance de l'Organisation mondiale de la santé pour les nourrissons et les jeunes enfants.

The growth pattern of healthy breastfed infants deviates to a significant extent from the NCHS/WHO international reference. In particular, this reference is inadequate because it is based on predominantly formula-fed infants, as are most national growth charts in use today. The WHO multicentre growth reference study (MGRS), aimed at describing the growth of healthy breastfed infants living in good hygiene conditions, was conducted between 1997 and 2003 in 6 countries from diverse geographical regions: Brazil, Ghana, India, Norway, Oman and the United States. The study combined a longitudinal follow-up of 882 infants from birth to 24 months with a cross-sectional component of 6669 children aged 18-71 months. In the longitudinal follow-up study, mothers and newborns were enrolled at birth and visited at home a total of 21 times at weeks 1, 2, 4 and 6; monthly from 2-12 months; and bimonthly in the 2nd year. The study populations lived in socioeconomic conditions favorable to growth. The individual inclusion criteria for the longitudinal component were: no known health or environmental constraints to growth, mothers willing to follow MGRS feeding recommendations (i.e., exclusive or predominant breastfeeding for at least 4 months, introduction of complementary foods by 6 months of age and continued breastfeeding to at least 12 months of age), no maternal smoking before and after delivery, single-term birth and absence of significant morbidity. Term low-birth-weight infants were not excluded. The eligibility criteria for the cross-sectional component were the same as those for the longitudinal component with the exception of infant feeding practices. A minimum of 3 months of any breastfeeding was required for participants in the study's cross-sectional component. Weight-for-age, length/height-for-age, weight-for-length/height and body mass index-for-age percentile and Z-score values were generated for boys and girls aged 0-60 months. The full set of tables and charts is presented on the WHO website (www.who.int/childgrowth/en), together with tools such as software and training materials that facilitate their application. The WHO child growth standards were derived from children who were raised in environments that minimized constraints to growth, such as poor diets and infection. In addition, their mothers followed healthy practices such as breastfeeding their children and not smoking during and after pregnancy. The standards depict normal human growth under optimal environmental conditions and can be used to assess children everywhere, regardless of ethnicity, socioeconomic status and type of feeding. The standards explicitly identify breastfeeding as the biological norm and establish the breastfed child as the normative model for growth and development. They have the potential to significantly strengthen health policies and public support for breastfeeding. The pooled sample from the 6 participating countries allowed the development of a truly international reference that underscores the fact that child populations grow similarly across the world's major regions when their health and care needs are met. It also provides a tool that is timely and appropriate for the ethnic diversity seen within countries and the evolution toward increasingly multiracial societies in the Americas and Europe as elsewhere in the world. The WHO standards provide a better tool to monitor the rapid and changing rate of growth in early infancy. They also demonstrate that healthy children from around the world who are raised in healthy environments and follow recommended feeding practices have strikingly similar patterns of growth.

Construction of the World Health Organization child growth standards: selection of methods for attained growth curves.

The World Health Organization (WHO), in collaboration with a number of research institutions worldwide, is developing new child growth standards. As part of a broad consultative process for selecting the best statistical methods, WHO convened a group of statisticians and child growth experts to review available methods, develop a strategy for assessing their strengths and weaknesses, and discuss methodological issues likely to be faced in the process of constructing the new growth curves. To select the method(s) to be used, the group proposed a two-stage decision-making process. First, to select a few relevant methods based on a list of set criteria and, second, to compare the methods using available tests or other established procedures. The group reviewed 30 methods for attained growth curves. Using the pre-defined criteria, a few were selected combining five distributions and two smoothing techniques. Because the number of selected methods was considered too large to be fully tested, a preliminary study was recommended to evaluate goodness of fit of the five distributions. Methods based on distributions with poor performance will be eliminated and the remaining methods fully tested and compared.

Community-based supplementary feeding for promoting the growth of young children in developing countries.

BACKGROUND: Supplementary feeding is defined as the provision of extra food to poor children or families beyond the normal ration of their home diets. The impact of food supplementation on child growth merits careful evaluation in view of the reliance of many states and NGOs on this intervention to improve child health in developing countries. OBJECTIVES: To evaluate the effectiveness of community-based supplementary feeding for promoting the physical growth of pre-school children in developing countries. SEARCH STRATEGY: Searches of CENTRAL 2005 (Issue 2), MEDLINE 1966 to 2005, EMBASE 1980 to 2005, CINAHL 1982 to 2005, LILACS 1982 to 2005, Social Science Citation Index 1956 to 2005, and Dissertation Abstracts International (late 1960s to 2005) were conducted. SELECTION CRITERIA: Randomised controlled trials evaluating supplementary feeding in children aged 0-5 years old in developing countries. DATA COLLECTION AND ANALYSIS: Data were extracted and analysed independently by two authors. MAIN RESULTS: Four trials met the inclusion criteria for this review. No meta-analysis is currently appropriate due to the clinical heterogeneity among the included studies. We group these trials into two categories: a) studies without formally assessment of malnourishment at baseline and, b) studies involving children formally assessed as malnourished.a) A cluster RCT conducted in Indonesia in 1991(20 Day Care Centres, n = 113 children), found no benefit in weight-for-age and height-for-age z-scores of the intervention group compared to the control group after three months of intervention. A study in Guatemala included four villages as unit of analysis (exact sample sizes were not provided). The length of 3-yr-old children was based on a 'before-after comparison' by village size and type of supplement. According to this analysis, the difference in net change in the large villages was 2.55 cm and in the small villages was 2.35 cm. The mean of these differences is 2.45 +- 0.10 cm (mean +- SD).b) A study conducted in Jamaica (n = 65 children) reported a positive effect on length (cm) in the supplemented group compared to controls [WMD 1.3 (0.03 to 2.57)] after 12 months of intervention. A trial from Indonesia (n = 75 children) found no benefit in growth after 12 months of supplementation. AUTHORS' CONCLUSIONS: Based on the small number of available trials, no firm conclusions of the effectiveness of supplementary feeding to the growth of pre-school children could be drawn. Issues of research design such as blinding and sample size calculation need to be addressed in future studies.

The use of anthropometry in the prevention of childhood overweight and obesity.

OBJECTIVE: To review concepts and propose measures related to the use of anthropometry for early identification of excessive weight gain in children. METHODS: Review of results from national and international studies focusing on the assessment of childhood growth, and evaluation of the weight-for-height z-scores of individual children using the 1977 National Center for Health Statistics and the 2000 Centers for Disease Control and Prevention growth charts. RESULTS: At present, few countries (23%) use indicators based on weight and height measurements to classify child body weight status. Less than one-third of growth monitoring programmes assess the growth of children beyond 6 y of age. Growth charts based on descriptive samples of populations undergoing increasing trends of childhood overweight and obesity result in substantial underestimation of true rates of these conditions. CONCLUSION: Early recognition of excessive weight gain relative to linear growth should become standard clinical practice by the following: (a) the routine collection of height measurements to enable monitoring weight-for-height and body mass index (BMI); (b) the expansion of existing monitoring programmes to include the assessment of all children up to 18 y at least once a year; (c) the interpretation of weight-for-height and BMI indices based on prescriptive reference data; and (d) the early intervention after an increase in weight-for-height or BMI percentiles has been observed.

Factors associated with unconstrained growth among affluent Ghanaian children.

AIM: To identify socio-economic factors associated with unconstrained growth among children living in well-off neighbourhoods of Accra, Ghana. METHODS: A cross-sectional study involving the assessment of the anthropometric status of preschool children. Children (n = 309) between the ages of 12 and 23 mo who live in affluent communities in Accra, Ghana were recruited for the study. Weight, length and mid-upper arm circumference were taken. Information was collected on household demographics and socio-economic status, including parental education and household income. Associations between these variables and attained growth were analysed to establish cut-offs for screening children with unconstrained growth. RESULTS: The mean weight-for-age (WA), length-for-age (LA) and weight-for-length (WL) Z-scores of the sub-sample selected on the basis of high socio-economic criteria were -0.18, -0.40 and 0.16, respectively. Among these well-off children, 0% were underweight, 3.0% were stunted and 0% were wasted (Z-scores <-2). Factors associated with better anthropometric status were paternal education and household income. Two screening criteria combining the two variables were selected: polytechnic education and income > 1,000,000 cedis (435 US dollars) or university education and income > 200,000 cedis. CONCLUSIONS: The children experiencing unconstrained growth belonged to a sub-population of affluent households characterized by high paternal education and household income. This subpopulation was targeted for screening for the WHO Multicentre Growth Reference Study in Ghana.

Socioeconomic predictors of unconstrained child growth in Muscat, Oman.

We conducted a study to identify socioeconomic factors associated with unconstrained growth among preschoolers in Muscat, Oman. A sample of children born in 1995 and aged 28-43 months was drawn from the Child Health Registers of 2 health care centres. Sociodemographic data were collected by oral interview and maternal and child anthropometry measured. Regression analysis was used to identify socioeconomic indicators and cut-offs associated with unconstrained growth. Children from households with a monthly income > or = 800 Omani rials and mother's education > or = 4 years attained height-for-age levels comparable to the current international growth reference. By screening using this criterion, we could obtain a suitable sample for the World Health Organization Multicentre Growth Reference Study in Muscat.

Socioeconomic predictors of unconstrained child growth in Muscat, Oman

We conducted a study to identify socioeconomic factors associated with unconstrained growth among preschoolers in Muscat, Oman. A sample of children born in 1995 and aged 28-43 months was drawn from the Child Health Registers of 2 health care centres. Sociodemographic data were collected by oral interview and maternal and child anthropometry measured. Regression analysis was used to identify socioeconomic indicators and cut-offs associated with unconstrained growth. Children from households with a monthly income > or = 800 Omani rials and mother's education > or = 4 years attained height-for-age levels comparable to the current international growth reference. By screening using this criterion, we could obtain a suitable sample for the World Health Organization Multicentre Growth Reference Study in Muscat

The Centers for Disease Control and Prevention 2000 growth charts and the growth of breastfed infants.

AIM: To evaluate the performance of the 2000 Centers for Disease Control and Prevention (CDC) growth charts in comparison with the National Center for Health Statistics/World Health Organization (NCHS/WHO) reference as a tool for assessing growth in healthy breastfed infants. METHODS: Weight and length measurements were obtained from a pooled longitudinal sample of 226 healthy breastfed infants. Weight-for-age (WA), length-for-age (LA) and weight-for-length (WL) z-scores based on the CDC and NCHS/WHO references were computed for each child. Age-specific mean z-scores and proportions below and above specific cut-off points were calculated. RESULTS: Breastfed infants grow more rapidly in the first 2 mo of life and less rapidly from 3 to 12 mo in relation to the CDC WA curves. Similarly, breastfed infants experience greater linear growth than the CDC median until age 4 mo. Thereafter, the mean LA z-score declines until month 9. Apart from a 1-mo difference in the time when linear growth begins to falter, the pattern of growth is remarkably similar when compared with the two references. The growth trajectories indicate that infants in the CDC reference are heavier and shorter than the NCHS/WHO reference population. Combining the two measurements as WL reveals that higher weight overrides lower length in the CDC versus the NCHS population, thus the estimated prevalence of wasting is higher by the CDC reference. CONCLUSION: As was the case when compared with the NCHS/WHO reference, there are notable differences in the growth trajectory of breastfed infants examined against the CDC reference. A reference based on healthy breastfed infants is required if the growth patterns of infants following international feeding recommendations are to be correctly assessed.

Ecological study of effect of breast feeding on infant mortality in Latin America.

OBJECTIVE: To estimate the effect of exclusive breast feeding and partial breast feeding on infant mortality from diarrhoeal disease and acute respiratory infections in Latin America. DESIGN: Attributable fraction analysis of national data on infant mortality and breast feeding. SETTING: Latin America and the Caribbean. MAIN OUTCOME MEASURES: Mortality from diarrhoeal disease and acute respiratory infections and nationally representative breastfeeding rates. RESULTS: 55% of infant deaths from diarrhoeal disease and acute respiratory infections in Latin America are preventable by exclusive breast feeding among infants aged 0-3 months and partial breast feeding throughout the remainder of infancy. Among infants aged 0-3 months, 66% of deaths from these causes are preventable by exclusive breast feeding; among infants aged 4-11 months, 32% of such deaths are preventable by partial breast feeding. 13.9% of infant deaths from all causes are preventable by these breastfeeding patterns. The annual number of preventable deaths is about 52 000 for the region. CONCLUSIONS: Exclusive breast feeding of infants aged 0-3 months and partial breast feeding throughout the remainder of infancy could substantially reduce infant mortality in Latin America. Interventions to promote breast feeding should target younger infants.

The National Center for Health Statistics reference and the growth of Indian adolescent boys.

BACKGROUND: Few studies describing the growth of adolescents exist because of the difficulties in interpreting anthropometric data in this age group. OBJECTIVE: We describe the growth of adolescent boys from West Bengal, India, and assess the adequacy of using the National Center for Health Statistics (NCHS) reference data. DESIGN: A cross-sectional anthropometric survey was conducted in 818 Bengali boys from middle-class families. Anthropometric measurements were taken on each subject's birthday (+/-3 d) by use of standard measuring techniques. The NCHS reference data on height and body mass index (BMI) were used to estimate age-specific prevalences of stunting, thinness, and overweight. BMI was also assessed by using British, Dutch, and French reference data. The biological parameters of the adolescent growth spurt were estimated by using the Preece-Baines growth model. RESULTS: With use of the 5th percentile of the NCHS reference data, the prevalence of thinness was approximately 5 times (50.5%) that of stunting (11.2%). The median curves of the 3 European references lay between the Indian and NCHS samples and also yielded high prevalences of thinness when applied to the study sample. The prevalence of being at risk of overweight was low (4.2%). Mean age at peak height velocity was 13.0 y and peak height velocity was 7.0 cm/y. CONCLUSIONS: The NCHS reference data seem inadequate for this sample. Consideration should be given to developing appropriate reference data based on healthy adolescent populations from different ethnic groups. Issues of maturation-related variation in assessing growth during adolescence should be given particular attention.

Worldwide timing of growth faltering: implications for nutritional interventions.

OBJECTIVE: It is widely assumed that growth faltering starts at around 3 months of age, but there has been no systematic assessment of its timing using representative national datasets from a variety of countries. METHODOLOGY: The World Health Organization Global Database on Child Growth and Malnutrition includes the results of 39 nationally representative datasets from recent surveys in developing countries. Based on these data, mean z scores of weight for age, length/height for age, and weight for length/height were compared with the National Center for Health Statistics and Cambridge growth references, for children younger than 60 months. RESULTS: Mean weights start to falter at about 3 months of age and decline rapidly until about 12 months, with a markedly slower decline until about 18 to 19 months and a catch-up pattern after that. Growth faltering in weight for length/height is restricted to the first 15 months of life, followed by rapid improvement. For length/height for age, the global mean is surprisingly close to National Center for Health Statistics and Cambridge references at birth, but faltering starts immediately afterward, lasting well into the third year. CONCLUSIONS: These findings highlight the need for prenatal and early life interventions to prevent growth failure.

Is malnutrition declining? An analysis of changes in levels of child malnutrition since 1980.

Nutritional status is the best global indicator of well-being in children. Although many surveys of children have been conducted since the 1970s, lack of comparability between them has made it difficult to monitor trends in child malnutrition. Cross-sectional data from 241 nationally representative surveys were analysed in a standard way to produce comparable results of low height-for-age (stunting). Multilevel modelling was applied to estimate regional and global trends from 1980 to 2005. The prevalence of stunting has fallen in developing countries from 47% in 1980 to 33% in 2000 (i.e. by 40 million), although progress has been uneven according to regions. Stunting has increased in Eastern Africa, but decreased in South-eastern Asia, South-central Asia and South America; Northern Africa and the Caribbean show modest improvement; and Western Africa and Central America present very little progress. Despite an overall decrease of stunting in developing countries, child malnutrition still remains a major public health problem in these countries. In some countries rates of stunting are rising, while in many others they remain disturbingly high. The data we have presented provide a baseline for assessing progress and help identify countries and regions in need of populationwide interventions. Approaches to lower child malnutrition should be based on successful nutrition programmes and policies.

Prevalence and trends of overweight among preschool children in developing countries.

BACKGROUND: Obesity during childhood is a matter of growing concern. Several reports show increasing rates of obesity in developed countries, whereas the extent of the problem in developing countries remains unknown. OBJECTIVE: The aim of this study was to fill this gap by quantifying the prevalence and trends of overweight among preschool children in developing countries. DESIGN: One hundred sixty nationally representative cross-sectional surveys from 94 countries were analyzed in a standardized way to allow comparisons across countries and over time. Overweight was defined as a weight-for-height >2 SDs from the National Center for Health Statistics/World Health Organization international reference median. Prevalences of wasted children (< -2 SDs) are also presented to enable comparisons between both ends of the distribution. RESULTS: The global prevalence of overweight was 3.3%. Some countries and regions, however, had considerably higher rates, and overweight was shown to increase in 16 of 38 countries with trend data. Countries with the highest prevalences of overweight are located mainly in the Middle East, North Africa, and Latin America. Rates of wasting were generally higher than those of overweight; Africa and Asia had wasting rates 2.5-3.5 times higher than overweight rates. Countries with high wasting rates tended to have low overweight rates and vice versa. CONCLUSIONS: These estimates show that attention should be paid to monitoring levels and trends of overweight in children. This, however, should not be done at the expense of decreasing international commitments to alleviating undernutrition. The data presented confirm that undernutrition remains a major public health problem worldwide.

A new international growth reference for young children.

Growth references for children are among the most widely used instruments in public health and clinical medicine. A comprehensive review by the World Health Organization (WHO) of the use and interpretation of anthropometric data concluded that the present international growth reference for infants does not describe physiologic growth adequately; thus, a new anthropometric reference was recommended for young children from birth to 5 y. The approach taken by the WHO for development of a new reference is guided by the principle that anthropometric reference data must always reflect the functional context of their intended uses and an awareness of the consequences of their application. The new reference will be constructed from data to be collected in a longitudinal study of infants who will be exclusively or predominantly breast-fed for >/=4 mo with continued breast-feeding throughout the first year, and a cross-sectional study of infants and young children aged 18-71 mo. The sample will be drawn from >/=7 diverse geographic sites around the world. The adopted protocol is expected to provide a single international reference that represents the best standard possible of optimal growth for all children <5 y of age. Furthermore, documentation will be sufficient to allow for possible future revision of the reference as substantial new biological information on the growth of infants and young children becomes available.