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.     

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.     

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.     

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.     

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.     

儿童运动协调能力与生长发育水平的关联性研究

目的 初步探讨儿童运动协调能力与生长发育水平的关联性,为明确两者的因果关系,有效促进儿童的生长发育水平提供线索.方法 在上海市虹口、普陀、浦东3个区整群抽取10所幼儿园进行调查,共1099名儿童纳入分析,采用发育性协调障碍问卷(DCDQ)对儿童的运动协调能力进行评测.采用结构方程模型对运动协调能力与儿童生长发育水平之间的关联性进行分析,采用多组结构方程模型对不同性别、年龄和是否超重儿童的关联模型差别进行分析.结果 1099名研究对象中,男童561人(51％),女童538人(49％),3岁～组354人(32.2％),4岁～组441人(40.1％),5岁～组276人(25.2％),6～7岁组28人(2.5％).结构方程模型分析结果显示在儿童运动协调的功能表现中,精细运动、粗大运动和一般协调性均与生长发育水平呈正相关,具有统计学意义(标准化系数分别为0.36,0.40,0.37,P均＜0.001);多组结构方程模型分析结果显示不同性别和年龄的结构方程模型未发现明显差异(P均＞0.05),但超重和正常组的结构模型存在差异,其中仅粗大运动与儿童生长发育水平的结构系数存在组间差异(t值=1.697,P＜0.05).结论 儿童运动协调能力与生长发育水平存在一定关联性,并且超重和正常组儿童的粗大运动与生长发育水平的关联程度存在差异,为深入开展儿童生长发育水平影响因素的研究奠定了基础.     

Parental age and child growth and development: Child health check‐up data

Background: The aim of the present study was to determine whether parental age has any influence on child health. Methods: Well‐baby check‐up data at 1 month and at 12 months of age were used. The trends of parental age in association with growth measurements, incidence of physical and developmental abnormalities, occurrence of low birthweight, and maternal history of spontaneous abortion were analyzed. Results: Associations between increasing paternal age and incidence of psychomotor developmental delay at 12 months, increasing paternal and maternal age and increasing birthweight, and increasing parental age and higher incidence of history of spontaneous abortion were found. The incidence of low‐birthweight infants was significantly decreased with increasing paternal age. Conclusions: Not only increasing maternal age but also increasing paternal age have influences on child development and growth in the general population.     

Variations in early gross motor milestones and in the age of walking in Japanese children

Background: Gross motor development is usually assessed in terms of age of achievement of motor milestones. Although there is generally an impression of faster development if the milestones are achieved at younger ages, no longitudinal studies have been done on the associations between the milestones, especially in Japan. As a part of the Japan Children's Study, the purpose of the present study was to determine whether the achievement of gross motor milestones in infancy is related with the age of walking. Methods: This was a prospective cohort study of 290 healthy and term infants born in a district of Osaka City, Japan. Three milestones (rolling over, sitting, and crawling) were observed in the laboratory for infants aged at 4 and 9 months by a pediatrician and a developmental psychologist, and the age of walking was confirmed in questionnaires filled in by the parents at 18 and 27 months. Results: Children who could roll over at 4 months, and sit and crawl at 9 months, walked earlier than children who could not roll over, sit and crawl, respectively. With regard to crawling, children who were creeping had a 1 month delay in walking, and those who could not move forward had a 2 month delay compared to typical crawlers. On multiple regression analysis these three milestones were positively associated with walking: rolling over (β= 0.567), sitting (β= 1.973) and crawling (β= 1.473). Conclusion: The age and the patterns of sitting, crawling and rolling over were all related to the age of independent walking among Japanese infants. Consideration of milestone definition and variations is essential in medical check‐up.     

Child development at 5 years of age predicted mathematics ability and schooling outcomes in Malawian adolescents

Aim: This study aimed to examine the association between child development at 5 years of age and mathematics ability and schooling outcomes at 12 years of age in Malawian children. Methods: A prospective cohort study looking at 609 rural Malawian children. Outcome measures were percentage of correctly answered mathematics questions, highest school grade completed and number of times repeating school grades at 12 years of age. A child development summary score obtained at 5 years of age was the main exposure variable. Regression analyses were used to estimate the association and adjust for confounders. Sensitivity analysis was performed by handling losses to follow‐up with multiple imputation (MI) method. Results: The summary score was positively associated with percentage of correctly answered mathematics questions (p = 0.057; p = 0.031 MI) and with highest school grade completed (p = 0.096; p = 0.070 MI), and negatively associated with number of times repeating school grades (p = 0.834; p = 0.339 MI). Fine motor score at 5 years was independently associated with the mathematic score (p = 0.032; p = 0.011 MI). The association between child development and mathematics ability did not depend on school attendance. Conclusion: Child development at 5 years of age showed signs of positive association with mathematics ability and possibly with highest school grade completed at 12 years of age.     

Role of micronutrients for physical growth and mental development

Due to control of florid and severe cases of protein-energy malnutrition, deficiencies of micronutrients in children have assumed public health importance. According to National Nutrition Monitoring Bureau of India, over 50% of apparently healthy looking children have subclinical or biochemical deficiencies of vitamin A, vitamins B₂, B₆, folate and vitamin C. Over two-third of children have clinical evidences of iron deficiency while deficiency of trace minerals like iodine and zinc is quite common in certain populations. Children have food preferences and they are quite fussy to take green leafy vegetables and fruits thus compromising their intake of micronutrients from dietary sources. The full genetic potential of the child for physical growth and mental development may be compromised due to subclinical deficiencies of micronutrients which are commonly referred to as “hidden hunger”. Micronutrients are required for the integrity and optimal functioning of immune system. Children with subclinical deficiency of micronutrients are more vulnerable to develop frequent and more severe common day-to-day infections thus triggering a vicious cycle of undernutrition and recurrent infections. A number of micronutrients are required for optimal physical growth and neuromotor development. Isolated deficiencies of micronutrients are rare in clinical practice and usually deficiencies of multiple micronutrients co-exist. The first 3 years of life are most crucial and vulnerable to the hazards of undernutrition. All efforts should be made so that preschool children are given a balanced and nutritious home-based diet. However, it has been shown that it is not possible to meet 100% requirements of recommended dietary allowances (RDA’s) of micronutrients from dietary sources alone and most preschool children need administration of nutritional supplements to optimize their genetic potential for physical growth and mental development.     

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 ≥ 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 socio-economic 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 diet and mother–child interactions mediate intervention effects on child growth and development

This study examined whether child diet and mother–child interactions mediated the effects of a responsive stimulation and nutrition intervention delivered from 2009 to 2012 to 1324 children aged 0–24 months living in rural Pakistan. Results showed that the intervention improved children''s cognitive, language and motor development through child diet and mother–child interactions. Although the intervention did not improve child growth or socio‐emotional development, we observed positive indirect effects on child growth via child diet and on socio‐emotional development via both child diet and mother–child interactions. In addition, child diet emerged as a shared mechanism to improve both child growth and development, whereas mother–child interactions emerged as a distinct mechanism to improve child development. Nevertheless, our results suggest the two mechanisms were mutually reinforcing and that interventions leveraging both mechanisms are likely to be more effective at improving child outcomes than interventions leveraging only one of these mechanisms.