Normal variation in human growth

The growth of children mirrors their health and the environment in which they thrive, and is therefore widely used as proxy for health of individual children and the population to which they belong. The assessment of growth may involve a single measurement of attained size (distance), the timely occurrence of an event (tempo), the rate of growth between two measurements (velocity), or patterns of growth over several years. In this study, we developed cross-sectional references of length, height, weight, Body Mass Index (BMI), head circumference, and pubertal development from a representative sample of Flemish children. Sampling and data collection were up to current standards, and growth distance curves were fitted with the LMS method. Results show an ongoing secular trend in height of 0.8 1.2 cm per decade within the Belgian population. Height of Belgian children is roughly comparable with that in other northern European countries, except for the Netherlands. The BMI curve, and consequently the prevalence of overweight, is also largely comparable with that in neighbouring countries. References for pubertal development were estimated from status presens data using generalized additive models. Mean age at menarche has not changed over the past 50 years. Menarche and the development of secondary sex characteristics are within ranges that are observed in northern Europe. Our references for BMI and Tanner stages of pubertal development are the first for the Belgian population.The assessment of changes in size over time requires appropriate instruments based on longitudinal data. We validated conditional growth based on the correlation between measurements converted to standard deviation scores (SDS), which is equivalent to the change in position on a growth distance chart. Correlations between serial measurements of length, weight and head circumference were estimated from longitudinal data of infants and primary schoolchildren. The correlation structure of weight and height SDS was comparable with similar data from the UK and France. References for conditional growth in length and head circumference in infancy were not previously available.The perspective given by our study is that of the normal healthy child, and is therefore a proxy for the specificity or false positive rate of growth assessment. This rate has been shown to increase when children are frequently assessed. From a systematic analysis of referral patterns we devised and validated a method to estimate the total referral rates of growth monitoring programs from the joint distribution of measurements.Growth references show how children grow in a particular population at a particular time. The World Health Organization (WHO) universal standards are based on the attractive but controversial premise that all children grow alike under optimal feeding and environmental conditions. However, our analysis of growth in Belgian and Norwegian children that complied with these criteria shows that children grow more alike the local reference population. In our sample, as well as in other western populations, we observe shortly after birth a decrease in length and weight relative to the standards. This could be the result of a in our opinion too strict application of inclusion criteria by the WHO. Our findings for head circumference were later confirmed in the United Kingdom and in the United States, and indicate persistent population differences of anthropometric characteristics.The tools that were developed in this study give guidance for the assessment of growth in individual children, and for the development and evaluation of guidelines and programs for growth monitoring.Preface/Acknowledgments Summary Samenvatting Table of contents Abbreviations Introduction 1. Normal growth and development 1.1 The assessment of growth and development 1.2 Growth charts 1.3 Normal growth 1.4 Criteria for overweight 1.5 Growth standards 1.6 Summary and conclusions 2. Objectives 3. Materials and methods: The Flemish growth study 4. Results 4.1 References for growth and pubertal development from birth to 21 years in Flanders, Belgium 4.2 Breastfeeding, growth and growth standards: Performance of the WHO growth standards for monitoring growth of Belgian children 4.3 Growth of Belgian and Norwegian children compared to the WHO growth standards: prevalence below -2 and above +2SD and the effect of breastfeeding 4.4 Conditional growth and correlations between longitudinal measurements of length, height, weight and head circumference in infancy and childhood 4.5 Referral rates for serial measurements of growth 5. Discussion 5.1 A cross-sectional growth distance reference 5.2 References or universal standards 5.3 Monitoring changes in growth over time 5.4 Referral rates of growth monitoring programs 5.5 Some final remarks 5.6 Future perspectives 6. Summary and conclusions References Appendix: Flemish Growth Charts 2004nrpages: 157status: publishe