Growth Prof Dr Müjgan Alikaşifoğlu
Why growth is important? • Which factors influence growth • Fetal and postnatal growth (height, weight) • Statistics used in describing growth • Assesment of physical growth • Techniques of physical measurements • Other indices of growth
Growth and Development • The basic science of pediatrics is growth and development. • People dealing with children’s health should be familiar with the normal patterns and milestones so that they can recognize overt deviations from the normal ranges as early as possible, in order for underlying disorders to be identified and given appropriate attention.
Growth and Development • Growth and development refers to the process by which the fertilized ovum eventually attains adult status. • Growth principally implies changes in size of the body as a whole or of its seperate parts. • Development principally involves changes of function.
Growth and Development • Growth is not determinedsolely by genetics. Environment also plays an importante role. • Heigth, for example, is a function of a child’s genetic endowment (biologic), personal habits of eating (psychologic), and access to nutrious food (social).
Fetal growth and development • The most dramatic events in growth occur before birth. • During early prenatal development the pattern of growth is largely dictated by the fetal genome, but as body size increases the fetus become constained by maternal and environmental influences such as uterine bloodflow, maternal size and maternal disease. • Fetal growth involves a massive cell hyperplasia while, postnatal growth involves more cell hypertrophy than hyperplasia.
Fetal growth and development • These differing patterns of growth have different hormonal requirements; the major growth promoting hormones in postnatal life, GH and thyroxine, having little apparent influence on human fetal growth. • These hormones do not cross the placenta in physiologically important quantities.
Fetal growth and development • Placenta acts as an endocrine gland. • One of the important function of placenta is, to syntesizes the hormones such as placental prolactin, eustrogen, progesteron and chorionic gonodotrophin which influence fetal growth and maintaining of pregnancy.
Fetal growth Embryonic period (0-8 wk): • By the end of wk 8, as the embryonic period closes; the average embryo weight 9 gr and has a crown-rump length of 5cm.
Fetal growth and development Fetal period: • From the 9th wk on somatic changes consist of increases in cell number and size and structural remodeling of several organ system. • By 10 wk, the face is recognizably human. • By 12 wk, the gender of the external genital becomes clearly distinguishable • During the 3rd trimester, weight triples and length doubles as body stores of protein, fat, iron and calcium increase.
Genetic, hormonal, and environmental influences on fetal growth Genetic and fetal factor • Race, gender • Congenital anomalies • Chromosomal disorders • Fetal hormons (insulin, corticosteroids, thyroid hormone, androgens) • Growth factors (IGF I, IGF II, TGF-α)
Genetic, hormonal, and environmental influences on fetal growth Maternal uterine environment • Uterine and placental anatomy • Utero-placental function • Human placental lactogen • Substrate fluxes and transfer • Uterine blood flow • Maternal systemic disease
Genetic, hormonal, and environmental influences on fetal growth Macroenvironment • Infectious agents (TORCH-S) • Diet and nutrion • Social and emotional stress • Drug and smoking • Teratogens and toxins • Altitude and temperature • Ionizing radiation
The first year of life • At term human male is larger than the female, by 150 gr on average. • The sex related difference in body weight becomes apparent from 34 weeks gestation • Birthweight shows considerable variation within race, ethnic groups, and individual families, the last being related to parental height and weight. • A newborn weight may decrease 10 % below birthweight in the 1st wk as a result of excreation of excess extravascular fluid and possible poor intake.
The first year of life • Infants should regain or exceed birthweight by 2 wk of age and should grow at approximately 30g/day during the 1st mounth. • Between 3 and 4 mo, the rate of weight gain slows to approximately 20g/day. • Weight gain in the first 6 mo= 150-200 gr/wk, at least 600 gr /mo
The first year of life • Between 6-9 mo, 15 g/day • Between 9-12 mo, 12g/day • Weight gain in the second 6 mo= 100-150 gr/wk, at least 400 gr/mo • The fullterm infant will generally double birthweight by 5 mo and triple it by 1 year.
The first year of life 3-12 mo Weight= age (mo) + 9/ 2 kg
The first year of life Lenght: • The lenght of a normal infant increases during the 1st year by 25-30 cm • First two trimenon= 8 cm/three months • Second two trimenon= 4 cm/ three months
The first year of life An increase in subcutaneous tissue in the early months of life reaches it peak at about 9 mo.
The second year • The growth rate slows further in the 2 nd yr of life and appetite declines. • An average child will gain about 2,5 kg in weigth and about 12 cm in height
Preschool years Between the ages of 2 and 5 yr, the average child gains approximately 2 kg in weigth and 7 cm in height per year
Middle childhood • Growth during the period :3-3.5 kg and 5- 6 cm per year. • Growth of the midface and lower face occurs gradually.
Middle childhood Weight • 1-6 yr: age (yr)x2+8 • 7-12 yr: age(yr)x7-5/2 Height • 2-12 yr: age(yr)x6+77 Or • 3-6 yr: age(yr)x5+80 • 6-11yr: age(yr)x5+84
Statistics used in describing growth • In everyday use the term normal is synonymous with healthy. • In a statistical sense, normal means that a set of values generates a normal (bell-shaped) distribution. • This is the case with anthropometric quantities such as height and weight.
Statistics used in describing growth • For a normally distributed measurement, a histogram with the quantity (e.g. height, or age) on the x-axis and the frequency (the number of children of that height) on the y-axis generates a bell-shaped curve. • In an ideal bell-shaped curve, the peak corresponds the arhitmetic mean of the sample, and to the median and the mode as well.
Statistics used in describing growth • The median: is the value above and belove which 50% of the observations lie • The mode: is the value having the highest number of observations • The extend to which observed values cluster near the means determines the width of the bell and can be described mathematically by the standard deviation (SD).
Statistics used in describing growth • SD measures the degree of dispersion of observed values as they deviate from the mean value. • In the ideal normal curve, a range of values extending from 1 SD below the mean to 1 SD above the mean includes approximately 68% of the value
Statistics used in describing growth • A range encompasing ± 2 SD includes 95% of the values • ± 3 SD encompases 99.7% of the values.
Relationship between SD and normal range for normally distributed quantities
Example: If the population measured is healthy boys and individual boy’s height falls more than 2 SD belove the mean, than the probability that this boy belongs to the population of healthy boys is less than 2.3 %
Statistics used in describing growth • A measurement that falls “outside the normal range”- arbitarily defined as 2, or sometimes 3 SD on either side of the mean- is atypical, but not necessarily indicative of illness. • However, the further a measurement falls from the mean, the greater the probability that it represents not simply the normal variation, but rather a different, potentially pathologic, condition.
Statistics used in describing growth • Percentiles: Another way of relating an individual to a group. • The percentile is the percentage of individuals in the group who have achieved a certain measured quantity (e.g., a height of 95 cm).
10 % of observations fall below the 10th percentile, • 90 % below the 90th percentile.
Statistics used in describing growth • For anthropometric data, the percentile cutoffs can be calculated from the mean and SD. • The 5th percentile corresponds to – 1.65 SD • The 10th percentile corresponds to – 1,3 SD • The 25th percentile corresponds to -0,7 SD
In this figure shows how frequency distributions of height at different ages relate to the percentile lines on the growth curve.
The above measures of dispersion are commonly used to locate an individual member of a population with respect to the average member
On the weight chart for girls 0-36 mo of age. • The 9 mo age line intersects the 25th percentile curve at about 8 kg (75% weigh more). Similarly a 9 mo-old girl wieghing more than 10.2 kg is heavier than 95% of her peers • By definition, the 50th percentile is the median It is also termed the standard value in the sense that the standard weight for a 9 mo girls is about 8.5 kg • +/- 10cm.
Assesment of physical growth Three principal phases of growth is childhood: • Rapid and rapidly decelerating growth of the first 3 years • The steady and slowly decelerating growth of mid-childhood • The growth of adolescence
Assesment of physical growth • The infancy component of growth appears to be largely nutritionally determined. • Childhood component; the earliest onset could be recognized at 6 months of age. • Until the age of 3 years growth is a combination of the infancy and childhood components acting additively • The childhood component is mostly dependent on growth hormon • Pubertal component depends on synergism between sex steroids and growth hormon
Assesment of physical growth • Weight, weight velocity • Height, height velocity • Head circumference, velocity of the increase in head circumference • Body proportions • Chest circumference
Assesment of physical growth • The most powerful tool to growth assessment is the growth chart. Growth chart interpretation • For infants, the measure of lineer growth is length, taken by two examiners (one to position the child) with the child supine on a measuring board. • For older children, the measure is stature, taken with a child standing on a stadiometer. • This technical difference results in children’s appearing to shift down in length as they change from the younger to the older chart.
Assesment of physical growth • The data are presented in five standart charts: • Weigth for age • Height (length and stature) for age • Head circumference for age • Weight for height • BMI
Assesment of physical growth • Measurements of weight, height and head circumference at any given time will indicate the status of a child with respect to other children of the same age but only sequential measurements will indicate the quality of the process through which each child is achieving his or her growth potential.
Height velocity calculation • Care should be taken in choosing the time interval between height measurements used in a velocity calculation. • Time intervales of less than 6 mo will exaggerate measurement errors and a whole year velocity is more appropriate. • A child with a height velocity below the 25th centile consistently needs to be investigated.
Height velocity calculation • The advantage of using velocity as a criterion of normality is that it detects abnormal growth regardless of stature achieved.
Assesment of physical growth Another way to describe extremes of height is the height age, the age at which the standard (median) height equals the child’s present height.
A 30-mo-old child who is as tall as an average 12 mo old has a height age of 12 mo. • The weight age is defined analogously
Analyses of growth patterns • Growth is a process rather than a static quality. • An infant at the 5th percentile of weight for age may be growing normally, may be failing to grow, or may be recovering from growth failure, depending on the trajectory of the growth curve. • Typically, infants and children stay within one or two growth channels. • A normal exception commonly occurs during the 1st year of life. For full term infants, size at birth reflects the influence of the uterine environment • Size at age 2 yr correlates with mean parental height, reflecting the influence of genes.
Analyses of growth patterns • Between birth and 18 mo, small infants often shift percentiles upward toward their parents’ mean percentile. • Large neonates often shifts downward, with decelerating growth beginning at 3-6 mo and ending as an infant achieves a new growth channel at approximately 13-18 mo.
Analyses of growth patterns • For children with particularly tall or short parents, there is a risk of overdiagnosing growth disorders if parental height is not taken into account or, conversely, of underdiagnosing growth disorders if parental height is accepted uncritically as the explanation