Growth

Growth

Prof Dr Mjgan Alikaifolu

Why growth is important?Which factors influence growthFetal and postnatal growth (height, weight)Statistics used in describing growth Assesment of physical growthTechniques of physical measurementsOther indices of growth

Growth and DevelopmentThe basic science of pediatrics is growth and development. People dealing with childrens 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 DevelopmentGrowth 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 DevelopmentGrowth is not determined solely by genetics. Environment also plays an importante role.Heigth, for example, is a function of a childs genetic endowment (biologic), personal habits of eating (psychologic), and access to nutrious food (social).

Fetal growth and developmentThe 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 developmentThese 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 developmentPlacenta 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 developmentFetal 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 distinguishableDuring 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 growthGenetic and fetal factorRace, genderCongenital anomaliesChromosomal disordersFetal hormons (insulin, corticosteroids, thyroid hormone, androgens)Growth factors (IGF I, IGF II, TGF-)

Genetic, hormonal, and environmental influences on fetal growthMaternal uterine environmentUterine and placental anatomyUtero-placental functionHuman placental lactogenSubstrate fluxes and transferUterine blood flowMaternal systemic disease

Genetic, hormonal, and environmental influences on fetal growthMacroenvironmentInfectious agents (TORCH-S)Diet and nutrionSocial and emotional stressDrug and smokingTeratogens and toxinsAltitude and temperatureIonizing 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 gestationBirthweight 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/dayBetween 9-12 mo, 12g/dayWeight gain in the second 6 mo= 100-150 gr/wk, at least 400 gr/moThe 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 cmFirst two trimenon= 8 cm/three monthsSecond 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

Weight1-6 yr: age (yr)x2+87-12 yr: age(yr)x7-5/2Height2-12 yr: age(yr)x6+77Or3-6 yr: age(yr)x5+806-11yr: age(yr)x5+84

Statistics used in describing growthIn 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 growthFor 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 growthThe median: is the value above and belove which 50% of the observations lieThe mode: is the value having the highest number of observationsThe 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 growthSD 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

Observation included in normal rangeProbability of a normal measurement deviating from mean by this amountSD%SD% 168.3 116 295.4 22.3 399.7 30.13

Example: If the population measured is healthy boys and individual boys 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 growthA 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 growthPercentiles: 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 growthFor anthropometric data, the percentile cutoffs can be calculated from the mean and SD. The 5th percentile corresponds to 1.65 SDThe 10th percentile corresponds to 1,3 SDThe 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 peersBy 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 growthThree principal phases of growth ischildhood:Rapid and rapidly decelerating growth of the first 3 yearsThe steady and slowly decelerating growth of mid-childhoodThe growth of adolescence

Assesment of physical growthThe 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 additivelyThe childhood component is mostly dependent on growth hormonPubertal component depends on synergism between sex steroids and growth hormon

Assesment of physical growthWeight, weight velocityHeight, height velocityHead circumference, velocity of the increase in head circumferenceBody proportionsChest circumference

Assesment of physical growth

The most powerful tool to growth assessment is the growth chart. Growth chart interpretationFor 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 childrens appearing to shift down in length as they change from the younger to the older chart.

Assesment of physical growthThe data are presented in five standart charts:Weigth for ageHeight (length and stature) for ageHead circumference for ageWeight for heightBMI

Assesment of physical growthMeasurements 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 calculationThe 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 childs 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 environmentSize 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

Target HeightPrediction of target heightFor girls: (Father height- 13)+mother height/2For boys: (Mother height+13)+ father height/2This gives the range of adult height (+/- 10cm) that would occur in 95% of the offspring of the parents in question.It is of diagnostic importance if predicted adult height falls below this target range.

Analyses of growth patterns

The analysis of a growth patterns provides critical information for the diagnosis of growth failure. There is no universally agreed-on criterion for growth failure; most consider the diagnosis if a childs weight is below the 5th percentile or drops down more than two major percentile lines. Weight-for-height below the 5th percentile remains the single best growth chart indicator of acute undernutrition.Children, who have been chronically malnurished may be short as well as thin, so that their weight-for-height curves may appear relatively normal.

Techniques of physical measurements

Accurate measurement of weight and length is of obvious importance. Scales should be calibrated regularly.HeightSupine measurement- lengthIn the younger child who can not stand less than 3 years of age.

Techniques of physical measurementsSupine measurement- lengthOne person ensures the head is correctly positioned with the fixed upright headboard. A movable upright footboard is brought firmly against the heel.The feet should be flat against the footboard

The child is positioned against a vertical surface Shoes and socks should be removedThe feet should be together and flat on the ground with the heels touching the backboard or wall The legs should be straight with the buttocks and the scapulae against the backboard (heels, buttocks, upper part of the back, occiput against the vertical upright)The arms should hang naturally at the sides.

The lower margins of the orbit should be in the same horizontal plane as the external auditory meatusThe headbord of the apparatus should then be placed carefully on the head (the external audotory meatus and the lower border of the orbit should be in a place parallel with the floor)

Techniques of physical measurementsOne point to remember for accurate measuremets is the diurnal variation in height.As a consequence of gravity on the intervertebral discs, the diurnal variation in stature can be as much as 20 mm although the average variation is about 7-8 mm.Diurnal variation in height can be overcome by exerting firm but gentle pressure on the mastoid processes during measurements to stretch the spine.

Techniques of physical measurementsWeight preferably in the nude or in minimal underclothes

Techniques of physical measurements

Chest circumference Measurement is made midinspiration at the level of the xiphoid cartilage or substernal notch. Measurement is made with the child recumbent up to age 5 year and standing thereafter

Other indices of growth Body proportion

Body proportions follow a sequence of regular changes with development.The head and trunk are relatively large at birth, with progressive lengthening of the limbs throughout development, particularly during puberty.Proportionality can be assesses by measuring the lower body segment, defined as the length from the symphysis pubis to the flor, and the upper body segment, defined as the height minus the lower body segment.

Other indices of growth Body proportion

The ratio of upper body segment divided by lower body segment equals approximately 1.7 at birth, 1.3 at 3 yr of age, and 1.0 after 7 yr of age.Higher U/L ratios are characteristics of short-limb dwarfizm or bone disorders such as rickets.

Other indices of growth Skeletal Maturation

Ossification of the fetal skleton begins at about 5th mo. The distal femoral and proximal tibial epiphyses are usually ossified in the normal fullterm infant. A general index of growth status is given by the bone age as determined from reuntgenograms. We need reference standards to calculate bone age. The most commonly use reference standards are those of Gruelich and Pyle, which require radiographs of the left hand and wrist; knee films are sometimes added for younger infants.

Other indices of growth Skeletal MaturationSince girls are more advanced than boys in skletal development at all ages, seperate standards are necessary.

Other indices of growth Dental development

Dental development includes mineralization, eruption, and exfoliation.Initial mineralization begins as early as the second trimester (mean age for central incisors, 14wk) and continues through 3 yr of age for the primary teeth and 25 yr of age for the permanent teeth.Eruption begins with the central incisors and progresses laterally

Other indices of growth Dental developmentExfoliation begins at about 6 yr of age and continues through 12 yr of age.Eruption of the permanent teeth may follow exfoliation immediately or may lag 4-5 mo. The timing of dental development is poorly correlated with other processes of growth and maturation.Delayed eruption is usually considered when there are no teeth by approximately 13 mo of age.Common causes: HypothyroidHypoparathyroidFamilialIdiopatic (the most common)

Other indices of growth Physiologic and structural growth

Respiratory rate and pulse rate decrease throughout childhoodBlood pressure rises begining at 6 yr of ageDevelopment of the paranasal sinuses continues throughout childhood.The ethmoids and sphenoid sinuses are present from birth, the frontal sinuses first appear radiologically around 6 yr of age.

Other indices of growth Physiologic and structural growthLymphoid tissues develop rapidly, reaching adult size by 6 yr of age and continuing to hipertrophy throughout childhood and early adolescence before receding to adult size.Nutritional needs as well as a wide variety of biochemical and hematologic values undergo marked developmental changes. For example, the alkalene phosphatase level increases during periods of rapid bone growth.

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