Growth pattern in children - concept and factors

The sequence, pattern and direction of changes in growth in children

1. Growth in children

2. Introduction Growth refers to quantitative changes in the body. The main indicators of growth are increase in height, weight and changes in the body structure and body proportions. Changes continue to occur in all domains of development but changes that take place in the physical development of children become most visible and apparent. One of the important features of growth is that these changes are measurable. The sequence , pattern and direction of changes in growth are common to all children although the rate of growth may vary from one child to another.

3. Concept of growth The growth process of a child starts from conception into a fully mature adult. The terms 'growth' and 'development' are often used together but are not interchangeable because they represent two different facets of change dynamics, i.e., quantity and quality. At the early embryonic stage, fetal cells divide and differentiate to form tissues and organs. In the latter half of pregnancy and early childhood, there is also an increase in cell size that manifests as an increase in the protein-to- DNA ratio. The cell size continues to enlarge until about 10 years of age. The body cells remain in dynamic equilibrium; hence aging cells are continuously replaced by new cells. The rate of turnover of cells in different tissues is variable.

4. Biology of growth Laws of growth: The growth and development of children is a continuous and orderly process. There are specific periods in a child's life when the growth rate is steady, accelerates, or decelerates . The fetus grows fast in the first half of gestation. After that, the growth rate is slowed until the baby is born. The growth velocity is high in the early postnatal period , especially in the first few months . After that, there is a slower but steady growth during mid-childhood. The second phase of accelerated growth occurs at puberty. Growth decelerates after that for some time and then ceases altogether.

5. Periods of growth

6. The growth pattern of every individual is unique: The order of growth is cephalocaudal and distal to proximal . During fetal life, the growth of the head occurs before that of the neck , and arms grow before the legs. Distal body parts , such as hands, increase in size before the upper arms. In postnatal life, the growth of the head slows down, but limbs continue to grow rapidly.

7. Different Tissues Grow at Different Rates Brain growth: The brain enlarges rapidly during the latter months of fetal life and early months of postnatal life. At birth, the head size is about 65-70% of the expected head size in adults. It reaches 90% of the adult head size in two years . The fetal period and the first two years area critical phase for brain development. Later periods are also important for acquiring neuromotor functions and cognitive abilities.

8. Lymphoid growth The growth of lymphoid tissue is most notable during the mid-childhood. During this period, the lymphoid tissue is overgrown, and its mass may appear larger than that of a fully mature adult. A sign of accelerated lymphoid growth is the frequent finding of large tonsils and palpable lymph nodes in normal children between 4 and 8 years.

9. Growth of body fat and muscle mass Body tissues can be divided into fat and fat-free (lean) components. The lean body mass includes muscle tissue, internal organs, and skeleton . The growth in lean body mass is primarily due to increased skeletal and muscle mass . Lean body mass correlates closely with stature. Taller children have greater lean body mass than shorter children of the same age. After the pubertal growth spurt, boys have greater lean body mass than girls. Body fat, a storehouse of energy , is primarily deposited in the subcutaneous adipose tissue . Girls have more subcutaneous adipose tissue than boys . Moreover, the sites and quantity of adipose tissue differ in girls and boys. Girls tend to add adipose tissue to breasts , buttocks , thighs, and back of arms during adolescence.

10. Skeletal growth Skeletal growth is a continuous process occurring throughout childhood and adolescence. It is steady until the pubertal growth spurt, when it accelerates and subsequently slows considerably. The skeleton matures once the epiphysis or growth plates at the end of long bones fuse to the shaft or diaphysis. This occurs by about 18 years in girls and 20-22 years in boys. The degree of skeletal maturation closely correlates with the degree of sexual maturation . Obesity/overweight is also associated with advancement in skeletal maturation. Skeletal maturation is assessed by noting the appearance and fusion of epiphysis at the ends of long bones .

11. Growth of gonads Gonadal growth is dormant during childhood and becomes conspicuous during puberty.

12. Bone a ge estimation Assessment of bone age postnatally is based on the number , shape, and size of epiphyseal centers, the size , shape, and density of the ends of bones. Bone age is typically assessed on the radiograph of left hand and wrist . The Greulich and Pyle (G&P) method is widely used techniques for estimating bone age (skeletal maturity) in children and adolescents . Bone age is estimated by comparing the radiograph to reference images in the Greulich and Pyle Atlas . The atlas contains standard radiographs for boys and girls from birth through 19 years (boys) and 18 years (girls ). Tanner–Whitehouse Method (TW Method )- Each bone is assigned a maturity stage (from A → I), based on ossification and epiphyseal development. Each stage has a numerical score . Scores are summed to give a maturity score , which is then converted into a bone age using standard reference tables.

13. Eruption of teeth For primary teeth, The teeth in the upper jaw erupt earlier than those in the lower jaw, except for lower central incisors and second molar. The first molars are the first permanent teeth to erupt.

14. Timing of dentition

15. Factors affecting growth Fetal Growth Fetal growth is influenced primarily by fetal , placental , and maternal factors . The fetus has inherent growth potential and grows into a healthy, appropriate-sized newborn under normal circumstances. Genetic potential: Intrauterine growth is mainly determined by the genetic potential of the fetus, with environmental and nutritional factors acting as modulators . There is a strong correlation of maternal weight and height with the birth weight. This so-called 'maternal constraint' limits overgrowth of the fetus, thus preventing dystocia, and conserving mother's ability to have further pregnancies . Sex: Boys are generally taller and heavier than girls at birth .

16. Fetal hormones and growth factors The most important endocrine factors regulating growth in fetal life are insulin , insulin-like growth factor (IGF)-1 and IGF-2 . Insulin is secreted by the fetal pancreas IGFs are chiefly produced by the placenta. An adequate supply of triiodothyronine (T3)derived from maternal free thyroxine (T4) is needed for fetal neurodevelopment. Fetal thyroid hormone production begins in the 12th week but is low, and maternal T4 is important throughout gestation. Glucocorticoids play an essential role, primarily towards the end of gestation , influencing the maturation of organs such as the liver , lungs, and GIT . Growth hormone , though present in high levels in fetuses, does not have a major influence on fetal growth.

17. Placental factors F etal weight directly correlates with placental weight at term . Fetal growth is highly dependent on the structural and functional integrity of the placenta. With advancing gestation, the weight of the placenta increases to cater to the baby's increased needs . The total villous surface area increases, the diffusion distance decreases , the fetal capillaries dilate, and the resistance in fetoplacental vasculature falls. This positive remodeling facilitates nutrient transport across the placenta.

18. Maternal factors The mother's own fetal and childhood growth , her current height and weight, and her nutrient intake at the time of conception and during pregnancy play a vital role in determining fetal size. Teen or advanced age , recent pregnancy, high parity, and anemia negatively influence fetal size and health. Maternal intake of tobacco(smoked or chewed) and drug or alcohol abuse also retard fetal growth. Obstetric complications such as pregnancy-induced hypertension, pre-eclampsia, and multiple pregnancies produce fetal growth restriction. Pre-existing chronic systemic disease (chronic kidney disease, congestive heart failure) and acquired infections (rubella, syphilis , hepatitis B, HIV, CMV, toxoplasmosis) may influence fetal growth. Maternal obesity, by increasing the risk of gestational diabetes, hypertension and pre-eclampsia, can also adversely affect fetal outcome.

19. Postnatal Period The c hild's growth during postnatal life is determined by genetic potential and internal and external influences . Genetic factors: Chromosomal disorders and mutations in specific genes can affect growth. Chromosomal defects like Turner syndrome and Down syndrome manifest as growth retardation . Certain single-gene disorders may also result in retardation of growth, e.g., Prader -Willi syndrome and Noonan syndrome. While most genetic disorders lead to short stature, some defects can also result in tall stature,e.g., Klinefelter syndrome and Sotos syndrome . Intrauterine growth restriction (IUGR): IUGR resulting in low birth weight constitutes a significant risk factor for postnatal malnutrition and poor growth. LBW increases the chances of being underweight, stunting, and wasting in the first five years of life. It is estimated that about 90%of infants born small for gestational age (SGA) catch-up in weight and length during first two years of life, but up to10% remain short.

20. Hormonal influence: Normal growth cannot proceed without the proper milieu of hormones in the body throughout childhood and adolescence. Absence of growth hormone or thyroxine results in poor linear growth , underscoring the importance of these factors in promoting growth. During adolescence, androgens and estrogens have an important influence on the growth spurt and final adult height . Sex : The pubertal growth spurt occurs earlier in girls, but the peak height velocity attained in puberty is lower than boys . The final mean difference in adult height of about 13 cm between males and females.

21. Nutrition: The growth of children suffering from protein-energy malnutrition, anemia, and vitamin deficiency is retarded . Calcium, iron, zinc, iodine, and vitamins A and D are closely related to growth and development disorders . On the other hand, overeating and obesity accelerate somatic growth during childhood, but with no effect on the final height . Infections : In low-resource settings, infections are among the commonest contributors to poor childhood growth . Persistent or recurrent diarrhea and respiratory tract infections are common causes of growth impairment . Systemic infections and parasitic infestations may also retard the velocity of growth . The attributable risk for stunting for five or more bouts of diarrhea before 24 months of age is 25 %. Trauma : A fracture at the end of a bone may damage the growing epiphysis and thus hamper skeletal growth.

22. Social Factors: Socioeconomic level: Children from families with high socioeconomic levels usually have a better nutritional state . They suffer from fewer infections because of better nutrition and hygienic living conditions. Poverty : Hunger , undernutrition, and infections, often associated with poverty, cause poor growth . Natural resources: Improved nutrition of children in the community is facilitated when there is a rise in gross national product and per capita income . Climate : The growth velocity may alter in different seasons , usually higher in spring and low in summer months. Infections and infestations are common in a hot and humid climate . Weather has a pivotal effect on agricultural productivity , ready availability of food, and capacity for strenuous labor by the population .

23. Emotional factors: Children from broken homes and orphanages do not grow and develop optimally. Anxiety , insecurity, and lack of emotional support and love from the family prejudice the neurochemical regulation of growth hormone release. Parents with a happy childhood and cheerful personalities are more likely to have children with similar countenances. Cultural factors: The community's methods of child-rearing and infant feeding are determined by cultural habits and conventions. There may be religious taboos against the consumption of particular types of food. These affect the nutritional state and growth performance of children. Parental education: Mothers with more education are more likely to adopt appropriate health-promoting behaviors, directly and indirectly influencing growth and development.

24. Assessment of physical growth Weight : The child's weight in the nude (for newborns or infants ) or in minimal light clothing and without foot wear, is recorded accurately on a lever or electronic weighing scale. The child must be placed in the middle of the weighing pan. Correct the zero error before weighing.

25. . Steps in weighing a small baby with mother/caregiver

26. 2. Length: Note: Measuring the length of a child lying on a mattress and using cloth tapes is inaccurate and not recommended

27. Height

28. 3 . Head circumference Hair ornaments are removed and braids undone . Using a non-stretchable tape, the maximum circumference of the head from the occipital protuberance to the supraorbital ridges on the forehead is measured.

29. 4 . Chest circumference The chest circumference is measure at the level of the nipples, midway between inspiration and expiration.

30. 5 . Mid-upper arm circumference To measure the mid-upper arm circumference (MAC)- 1 st mark a point midway between the tip of the acromion process of the scapula and the olecranon of the ulna on the left side. Take the measurement while the child keeps the arm by his side, straight at the elbow. Ensure the tape is tight enough to avoid any gap and compression of soft tissues.

31. Normal Growth It is difficult to define the normal pattern of growth precisely . Generally, it lies between the third and ninety-seventh percentiles. Most healthy children maintain their growth percentile on the growth charts as the years pass. A significant deviation in a child's plotted position on the growth chart can be due to a recent illness or over- or undernutrition. It is also essential to consider the gestational age of infants born prematurely. The duration of prematurity is subtracted from the infant's chronological age (corrected age). This correction, however, is not required after two to three years of age .

32. Weight The average birth weight is about 3 kg. During the first few days after birth, N ewborn loses extracellular fluid about 7 to10% of the body weight. R egain their birthweight by 10 days. Then gain weight at approximately 20-40 g/day for the first three months of life. After that, they gain about 400 g of weight every month for the remaining part of the first year. An infant usually doubles his birth weight by the age of 5 months . The birth weight triples at one year and is 4 times at two years of age . A child's weight at the age of 3 years is about 5 times that of the birth weight. The expected weight can be calculated at 5 years by multiplying the birth weight by 6, 7 years by 7, and 10 years by 10 On average, a child gains about 2 kg every year between the ages of 3 and 7 years and 3 kg per year until the pubertal growth spurt begins.

33. Length or height The infant measures approximately: 50 cm at birth, 60 cm at three months, 65 cm at six months, 70 cm at nine months, 75 cm at one year, and 87 cm at two years . A normal child gains about 6 cm in height every year until 12 years. After this, height increments vary according to the age at the onset of puberty. There is a marked acceleration of growth during puberty.

34. Head circumference (HC ) Head growth is rapid, especially in the first half of infancy. It reflects brain growth during this period. The head growth slows considerably after that . 34 cm on average at birth HC increases approximately 2 cm/month for the first three months , 1 cm per month between 3 and 6 months, and 0.5 cm per month for the rest of the first year of life. The head circumference is approximately – 40 cm at three months , 43 cm at six months, 46-47 cm at one year, and 48 cm at two years . By 12 years, it is 52 cm.

35. Chest circumference The chest circumference is about 3 cm less than the head circumference at birth. The circumference of the head and chest are almost equal by the age of 1 year. After that, the chest circumference exceeds the head circumference.

36. Approximate anthropometric values by age

37. Body mass index (BMI ) The formula to calculate BMI is the weight (kg)/height ( meter)². BMI is a better measurement than weight alone to assess obesity as well as undernutrition.

38. Growth charts Growth charts are a good tool for growth surveillance. If a child's growth measurements are plotted on a graph, the deviation in the child's growth from the normal pattern can be easily interpreted. The normal variation in growth is taken as values between the 3rd and 97th percentiles curves . Percentile curves represent frequency distribution curves . For example, the 25th percentile for height in a population would mean that the height of 75% of individuals is above , and 24% is below this value.

39. S tandard deviation score(SDS) In a normal distribution : Mean (average) corresponds to the 50th percentile . +1 SDS (z = +1) corresponds to about the 84th percentile . (Because ~84% of values fall below 1 SD above the mean.) –1 SDS (z = –1) corresponds to about the 16th percentile . (Because ~16% of values fall below 1 SD below the mean.) ±2 SDS (z = –2 to +2) covers roughly the 3rd to 97th percentiles . (About 95% of values lie within 2 SDs of the mean.)

40. Z scores In a population with observations in a typical Gaussian (normal) distribution, any individual value can be expressed as how many SDS it lies above or below the mean . This is the z-score for that observation. Thus, if a child's weight is 2 SDS below the mean, it is equivalent to - 2 z . If the value lies above the mean, z-score is positive; otherwise, it is negative . The formula for calculating the z-score is : z-score = Observed value - mean value Standard deviation z-score allows the comparison of different observations between individuals. For example, one can compare the height and weight of two individuals by obtaining the respective z-scores.

41. If a child’s weight is 2 SDS below the mean , then: Z =−2Z This corresponds to about the 2.3rd percentile (only about 2–3% of children weigh less). If another child’s weight is +1 SDS above the mean : Z =+1Z That’s around the 84th percentile (taller/heavier than 84% of peers).

42. Growth Standards Growth standards represent growth norms and can be presented in a tabular or graphical manner. These are obtained by either cross-sectional or longitudinal studies in large populations. Based on data obtained from US children, the National Center for Health Statistics ( NCHS )developed growth charts in 1977. In the year 2000, revised growth charts provided by CDC offered an improved tool to assess child health. Multicentre Growth Reference Study (MGRS)/WHO published new growth charts for infants and children up to 5 years of age in 2006.The MGRS was a community-based, multi-country project conducted in Brazil, Ghana, India, Norway, Oman, and the United States. over-nourishment. It provide curves of z-score for weight, length or height, weight for height, and head circumference for girls and boys up to 5 years of age. The Indian Academy of Pediatrics (IAP) has provided growth reference charts for children aged 5 to 18

43. Suggested growth monitoring in children at different ages Adapted from guidelines of Indian Academy of Pediatrics (2006) BMI-body mass index, SMR-sexual maturity rating

44. Plotting on Growth Charts and Interpretation Growth charts allow the plotting of growth parameters for an individual child against their age and allow monitoring of trends over time. Children growing normally will usually be between -2.0and +2.0 z-scores (2SD above and below the mean, or between 3rd and 97th percentiles). The growth of an individual child plotted over time is expected to track reasonably close to the same z-score. If the growth curve tends towards the median, it is usually not a problem. But if it tends away from the median, it may signal a problem or risk of a problem. The following situations may indicate a problem or suggest a risk : A child's growth curve crosses a major z-score line or two major centile lines . S harp incline or decline in the child's growth curve A growth curve that remains flat(stagnant)

45. Riya is an 18-month-old girl who weighs 8.5 kg and has a length of 73.5 cm. Her weight-for-length (b), weight-for-age, and head circumference are within normal range H er length-for-age (a) is below-2 z-score for age. Hence , she is stunted (but not wasted)

46. The weight-for-age growth curve of two boys is plotted . The boy's weight in the top line (red dots) tracks just above the median , indicating a healthy trend. The bottom line (blue dots)shows a boy's weight falling from his expected growth track and crossing the z-scores line indicating risk.

47. Weight-for-age plot showing abnormal stagnation of weight. Some examples for such a trajectory are repeated infections and celiac disease