Biomedical subjects

WHO Multicentre Growth Reference Study Group

Publications and source records attributed to WHO Multicentre Growth Reference Study Group.

12 recordsLinked to original sources

PubMed2006

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.

Body Height↗

PubMed2006

Comparison of the World Health Organization (WHO) Child Growth Standards and the National Center for Health Statistics/WHO international growth reference: implications for child health programmes.

OBJECTIVES: To compare growth patterns and estimates of malnutrition based on the World Health Organization (WHO) Child Growth Standards ('the WHO standards') and the National Center for Health Statistics (NCHS)/WHO international growth reference ('the NCHS reference'), and discuss implications for child health programmes. DESIGN: Secondary analysis of longitudinal data to compare growth patterns (birth to 12 months) and data from two cross-sectional surveys to compare estimates of malnutrition among under-fives. SETTINGS: Bangladesh, Dominican Republic and a pooled sample of infants from North America and Northern Europe. SUBJECTS: Respectively 4787, 10 381 and 226 infants and children. RESULTS: Healthy breast-fed infants tracked along the WHO standard's weight-for-age mean Z-score while appearing to falter on the NCHS reference from 2 months onwards. Underweight rates increased during the first six months and thereafter decreased when based on the WHO standards. For all age groups stunting rates were higher according to the WHO standards. Wasting and severe wasting were substantially higher during the first half of infancy. Thereafter, the prevalence of severe wasting continued to be 1.5 to 2.5 times that of the NCHS reference. The increase in overweight rates based on the WHO standards varied by age group, with an overall relative increase of 34%. CONCLUSIONS: The WHO standards provide a better tool to monitor the rapid and changing rate of growth in early infancy. Their adoption will have important implications for child health with respect to the assessment of lactation performance and the adequacy of infant feeding. Population estimates of malnutrition will vary by age, growth indicator and the nutritional status of index populations.

Breast Feeding↗

PubMed2006

Enrolment and baseline characteristics in the WHO Multicentre Growth Reference Study.

AIM: To describe the WHO Multicentre Growth Reference Study (MGRS) sample with regard to screening, recruitment, compliance, sample retention and baseline characteristics. METHODS: A multi-country community-based study combining a longitudinal follow-up from birth to 24 mo with a cross-sectional survey of children aged 18 to 71 mo. Study subpopulations had to have socio-economic conditions favourable to growth, low mobility and > or = 20% of mothers practising breastfeeding. Individual inclusion criteria were no known environmental constraints on growth, adherence to MGRS feeding recommendations, no maternal smoking, single term birth and no significant morbidity. For the longitudinal sample, mothers and newborns were screened and enrolled at birth and visited 21 times at home until age 24 mo. RESULTS: About 83% of 13 741 subjects screened for the longitudinal component were ineligible and 5% refused to participate. Low socioeconomic status was the predominant reason for ineligibility in Brazil, Ghana, India and Oman, while parental refusal was the main reason for non-participation in Norway and USA. Overall, 88.5% of enrolled subjects completed the 24-mo follow-up, and 51% (888) complied with the MGRS feeding and no-smoking criteria. For the cross-sectional component, 69% of 21 510 subjects screened were excluded for similar reasons as for the longitudinal component. Although low birthweight was not an exclusion criterion, its prevalence was low (2.1% and 3.2% in the longitudinal and cross-sectional samples, respectively). Parental education was high, between 14 and 15 y of education on average. CONCLUSION: The MGRS criteria were effective in selecting healthy children with comparable affluent backgrounds across sites and similar characteristics between longitudinal and cross-sectional samples within sites.

Child↗

PubMed2006

Breastfeeding in the WHO Multicentre Growth Reference Study.

AIM: To document how children in the WHO Multicentre Growth Reference Study (MGRS) complied with feeding criteria and describe the breastfeeding practices of the compliant group. METHODS: The MGRS longitudinal component followed 1743 mother-infant pairs from birth to 24 mo in six countries (Brazil, Ghana, India, Norway, Oman and the USA). The study included three criteria for compliance with recommended feeding practices that were monitored at each follow-up visit through food frequency reports and 24-h dietary recalls. Trained lactation counsellors visited participating mothers frequently in the first months after delivery to help with breastfeeding initiation and prevent and resolve lactation problems. RESULTS: Of the 1743 enrolled newborns, 903 (51.8%) completed the follow-up and complied with the three feeding criteria. Three quarters (74.7%) of the infants were exclusively/predominantly breastfed for at least 4 mo, 99.5% were started on complementary foods by 6 mo of age, and 68.3% were partially breastfed until at least age 12 mo. Compliance varied across sites (lowest in Brazil and highest in Ghana) based on their initial baseline breastfeeding levels and sociocultural characteristics. Median breastfeeding frequency among compliant infants was 10, 9, 7 and 5 feeds per day at 3, 6, 9 and 12 mo, respectively. Compliant mothers were less likely to be employed, more likely to have had a vaginal delivery, and fewer of them were primiparous. Pacifier use was more prevalent in the non-compliant group. CONCLUSION: The MGRS lactation support teams were successful in enhancing breastfeeding practices and achieving high rates of compliance with the feeding criteria required for the construction of the new growth standards.

Breast Feeding↗

PubMed2006

Complementary feeding in the WHO Multicentre Growth Reference Study.

AIM: To describe complementary feeding practices in the Multicentre Growth Reference Study (MGRS) sample. METHODS: Food frequency questionnaires and 24-h dietary recalls were administered to describe child feeding throughout the first 2 y of life. This information was used to determine complementary feeding initiation, meal frequency and use of fortified foods. Descriptions of foods consumed and dietary diversity were derived from the 24-h recalls. Compliance with the feeding recommendations of the MGRS was determined on the basis of the food frequency reports. Descriptive statistics provide a profile of the complementary feeding patterns among the compliant children. RESULTS: Complementary feeding in the compliant group began at a mean age of 5.4 mo (range: 4.8 (Oman)-5.8 mo (Ghana)). Complementary food intake rose from 2 meals/d at 6 mo to 4-5 meals in the second year, in a reverse trend to breastfeeding frequency. Total intake from the two sources was 11 meals/d at 6-12 mo, dropping to 7 meals/d at 24 mo. Inter-site differences in total meal frequency were mainly due to variations in breastfeeding frequency. Grains were the most commonly selected food group compared with other food groups that varied more by site due to cultural factors, for example, infrequent consumption of flesh foods in India. The use of fortified foods and nutrient supplements was also influenced by site-variable practices. Dietary diversity varied minimally between compliance groups and sites. CONCLUSION: Complementary diets in the MGRS met global recommendations and were adequate to support physiological growth.

Child Development↗

PubMed2006

Reliability of anthropometric measurements in the WHO Multicentre Growth Reference Study.

AIM: To describe how reliability assessment data in the WHO Multicentre Growth Reference Study (MGRS) were collected and analysed, and to present the results thereof. METHODS: There were two sources of anthropometric data (length, head and arm circumferences, triceps and subscapular skinfolds, and height) for these analyses. Data for constructing the WHO Child Growth Standards, collected in duplicate by observer pairs, were used to calculate inter-observer technical error of measurement (TEM) and the coefficient of reliability. The second source was the anthropometry standardization sessions conducted throughout the data collection period with the aim of identifying and correcting measurement problems. An anthropometry expert visited each site annually to participate in standardization sessions and provide remedial training as required. Inter- and intra-observer TEM, and average bias relative to the expert, were calculated for the standardization data. RESULTS: TEM estimates for teams compared well with the anthropometry expert. Overall, average bias was within acceptable limits of deviation from the expert, with head circumference having both lowest bias and lowest TEM. Teams tended to underestimate length, height and arm circumference, and to overestimate skinfold measurements. This was likely due to difficulties associated with keeping children fully stretched out and still for length/height measurements and in manipulating soft tissues for the other measurements. Intra- and inter-observer TEMs were comparable, and newborns, infants and older children were measured with equal reliability. The coefficient of reliability was above 95% for all measurements except skinfolds whose R coefficient was 75-93%. CONCLUSION: Reliability of the MGRS teams compared well with the study's anthropometry expert and published reliability statistics.

Anthropometry↗

PubMed2006

Reliability of motor development data in the WHO Multicentre Growth Reference Study.

AIM: To describe the methods used to standardize the assessment of motor milestones in the WHO Multicentre Growth Reference Study (MGRS) and to present estimates of the reliability of the assessments. METHODS: As part of the MGRS, longitudinal data were collected on the acquisition of six motor milestones by children aged 4 to 24 mo in Ghana, India, Norway, Oman and the USA. To ensure standardized data collection, the sites conducted regular standardization sessions during which fieldworkers took turns to examine and score about 10 children for the six milestones. Assessments of the children were videotaped, and later the other fieldworkers in the same site watched the videotaped sessions and independently rated performances. The assessments were also viewed and rated by the study coordinator. The coordinator's ratings were considered the reference (true) scores. In addition, one cross-site standardization exercise took place using videotapes of 288 motor assessments. The degree of concordance between fieldworkers and the coordinator was analysed using the Kappa coefficient and the percentage of agreement. RESULTS: Overall, high percentages of agreement (81-100%) between fieldworkers and the coordinator and "substantial" (0.61-0.80) to "almost perfect" (> 0.80) Kappa coefficients were obtained for all fieldworkers, milestones and sites. Homogeneity tests confirm that the Kappas are homogeneous across sites, across milestones, and across fieldworkers. Concordance was slightly higher in the cross-site session than in the site standardization sessions. There were no systematic differences in assessing children by direct examination or through videotapes. CONCLUSION: These results show that the criteria used to define performance of the milestones were similar and applied with equally high levels of reliability among fieldworkers within a site, among milestones within a site, and among sites across milestones.

Child Development↗

PubMed2006

Assessment of differences in linear growth among populations in the WHO Multicentre Growth Reference Study.

AIM: To assess differences in length/height among populations in the WHO Multicentre Growth Reference Study (MGRS) and to evaluate the appropriateness of pooling data for the purpose of constructing a single international growth standard. METHODS: The MGRS collected growth data and related information from 8440 affluent children from widely differing ethnic backgrounds and cultural settings (Brazil, Ghana, India, Norway, Oman and the USA). Eligibility criteria included breastfeeding, no maternal smoking and environments supportive of unconstrained growth. The study combined longitudinal (birth to 24 mo) and cross-sectional (18-71 mo) components. For the longitudinal component, mother-infant pairs were enrolled at delivery and visited 21 times over the next 2 y. Rigorous methods of data collection and standardized procedures were applied across study sites. We evaluate the total variability of length attributable to sites and individuals, differences in length/height among sites, and the impact of excluding single sites on the percentiles of the remaining pooled sample. RESULTS: Proportions of total variability attributable to sites and individuals within sites were 3% and 70%, respectively. Differences in length and height ranged from -0.33 to +0.49 and -0.41 to +0.46 standard deviation units (SDs), respectively, most values being below 0.2 SDs. Differences in length on exclusion of single sites ranged from -0.10 to +0.07, -0.07 to +0.13, and -0.25 to +0.09 SDs, for the 50th, 3rd and 97th percentiles, respectively. Corresponding values for height ranged from -0.09 to +0.08, -0.12 to +0.13, and -0.15 to +0.07 SDs. CONCLUSION: The striking similarity in linear growth among children in the six sites justifies pooling the data and constructing a single international standard from birth to 5 y of age.

Body Height↗

PubMed2006

Assessment of sex differences and heterogeneity in motor milestone attainment among populations in the WHO Multicentre Growth Reference Study.

AIM: To assess the heterogeneity of gross motor milestone achievement ages between the sexes and among study sites participating in the WHO Multicentre Growth Reference Study (MGRS). METHODS: Six gross motor milestones (sitting without support, hands-and-knees crawling, standing with assistance, walking with assistance, standing alone, and walking alone) were assessed longitudinally in five of the six MGRS sites, namely Ghana, India, Norway, Oman and the USA. Testing was started at 4 mo of age and performed monthly until 12 mo, and bimonthly thereafter until all milestones were achieved or the child reached 24 mo of age. Four approaches were used to assess heterogeneity of the ages of milestone achievement on the basis of sex or study site. RESULTS: No significant, consistent differences in milestone achievement ages were detected between boys and girls, nor were any site sex interactions noted. However, some differences among sites were observed. The contribution of inter-site heterogeneity to the total variance was < 5% for those milestones with the least heterogeneous ages of achievement (hands-and-knees crawling, standing alone, and walking alone) and nearly 15% for those with the most heterogeneous ages of achievement (sitting without support, standing with assistance, and walking with assistance). CONCLUSION: Inter-site differences, most likely due to culture-specific care behaviours, reflect normal development among healthy populations across the wide range of cultures and environments included in the MGRS. These analyses support the appropriateness of pooling data from all sites and for both sexes for the purpose of developing an international standard for gross motor development.

Child Development↗

PubMed2006

WHO Child Growth Standards based on length/height, weight and age.

AIM: To describe the methods used to construct the WHO Child Growth Standards based on length/height, weight and age, and to present resulting growth charts. METHODS: The WHO Child Growth Standards were derived from an international sample of healthy breastfed infants and young children raised in environments that do not constrain growth. Rigorous methods of data collection and standardized procedures across study sites yielded very high-quality data. The generation of the standards followed methodical, state-of-the-art statistical methodologies. The Box-Cox power exponential (BCPE) method, with curve smoothing by cubic splines, was used to construct the curves. The BCPE accommodates various kinds of distributions, from normal to skewed or kurtotic, as necessary. A set of diagnostic tools was used to detect possible biases in estimated percentiles or z-score curves. RESULTS: There was wide variability in the degrees of freedom required for the cubic splines to achieve the best model. Except for length/height-for-age, which followed a normal distribution, all other standards needed to model skewness but not kurtosis. Length-for-age and height-for-age standards were constructed by fitting a unique model that reflected the 0.7-cm average difference between these two measurements. The concordance between smoothed percentile curves and empirical percentiles was excellent and free of bias. Percentiles and z-score curves for boys and girls aged 0-60 mo were generated for weight-for-age, length/height-for-age, weight-for-length/height (45 to 110 cm and 65 to 120 cm, respectively) and body mass index-for-age. CONCLUSION: The WHO Child Growth Standards depict normal growth under optimal environmental conditions and can be used to assess children everywhere, regardless of ethnicity, socio-economic status and type of feeding.

Body Height↗

PubMed2006

WHO Motor Development Study: windows of achievement for six gross motor development milestones.

AIM: To review the methods for generating windows of achievement for six gross motor developmental milestones and to compare the actual windows with commonly used motor development scales. METHODS: As part of the WHO Multicentre Growth Reference Study, longitudinal data were collected to describe the attainment of six gross motor milestones by children aged 4 to 24 mo in Ghana, India, Norway, Oman and the USA. Trained fieldworkers assessed 816 children at scheduled visits (monthly in year 1, bimonthly in year 2). Caretakers also recorded ages of achievement independently. Failure time models were used to construct windows of achievement for each milestone, bound by the 1st and 99th percentiles, without internal demarcations. RESULTS: About 90% of children achieved five of the milestones following a common sequence, and 4.3% did not exhibit hands-and-knees crawling. The six windows have age overlaps but vary in width; the narrowest is sitting without support (5.4 mo), and the widest are walking alone (9.4 mo) and standing alone (10.0 mo). The estimated 1st and 99th percentiles in months are: 3.8, 9.2 (sitting without support), 4.8, 11.4 (standing with assistance), 5.2, 13.5 (hands-and-knees crawling), 5.9, 13.7 (walking with assistance), 6.9, 16.9 (standing alone) and 8.2, 17.6 (walking alone). The 95% confidence interval widths varied among milestones between 0.2 and 0.4 mo for the 1st percentile, and 0.5 and 1.0 mo for the 99th. CONCLUSION: The windows represent normal variation in ages of milestone achievement among healthy children. They are recommended for descriptive comparisons among populations, to signal the need for appropriate screening when individual children appear to be late in achieving the milestones, and to raise awareness about the importance of overall development in child health.

Child Development↗

PubMed2006

Relationship between physical growth and motor development in the WHO Child Growth Standards.

AIM: To examine relationships among physical growth indicators and ages of achievement of six gross motor milestones in the WHO Child Growth Standards population. METHODS: Gross motor development assessments were performed longitudinally on the 816 children included in the WHO Child Growth Standards. Six milestones (sitting without support, hands-and-knees crawling, standing with assistance, walking with assistance, standing alone, walking alone) were assessed monthly from 4 until 12 mo of age and bimonthly thereafter until children could walk alone or reached 24 mo. Failure time models were used 1) to examine associations between specified ages of motor milestone achievement and attained growth z scores and 2) to quantify these relationships as delays or accelerations in ages of milestone achievement. RESULTS: Statistically significant associations were noted between ages of achievement of sitting without support and attained weight-for-age, weight-for-length and BMI-for-age z scores. An increase of one unit z score in these indicators was associated with 3 to 6 d acceleration in the respective achievement age. Statistically significant associations also were noted between various milestone achievement ages and growth when 3- or 6-mo and birth length-for-age z scores were entered jointly in the failure time models. In these analyses, one unit z-score increase in length-for-age was associated with 1 to 3 d delay in the respective achievement age. CONCLUSION: Sporadic, significant associations were observed between gross motor development and some physical growth indicators, but these were quantitatively of limited practical significance. These results suggest that, in healthy populations, the attainment of these six gross motor milestones is largely independent of variations in physical growth.

Body Height↗