Measurements and Growth Charts

Recumbent length versus height

Because most babies younger than 10 to 12 months cannot stand alone and most toddlers refuse to stand still, any child younger than 2 years should be measured for length in the recumbent position. In children of this age group, recumbent length and standing height are not the same, the former being significantly greater. Standard growth charts for younger children are based on measurements of recumbent length. Various accurate measuring devices—some cheap, others more expensive—are available for determining recumbent length and height. The essential point is to use a stable, accurate, fixed device if both individual and serial measurements are to mean anything (Figs. 3-1 and 3-2). Accuracy is a must, but never more so than when there is the slightest concern about the child’s growth. To be absolutely sure, check all measurements at least twice, and never accept anyone else’s measurements as reliable.

FIGURE 3-1 Measuring length: the appropriate method of assessing linear growth in children younger than 2 years. Keeping the youngster entertained improves accuracy.

FIGURE 3-2 Measuring height: The apparatus should be fixed and accurate. The child should be positioned with the head and heels touching the back board.

Finally, never commit the unpardonable sin of eyeball approximation—as, unfortunately, many persons still do. Notoriously unreliable methods for measuring recumbent length include (1) putting pen or pencil marks on a piece of paper on which the baby is lying to approximate the location of the crown and heel and then removing the baby and measuring the distance between the marks, or (2) laying a tape measure beside or under the baby. These disreputable practices result in highly inaccurate measurements and can lead to unreliable charting of growth and misdiagnoses of disproportion between linear and ponderal growth.

Head circumference

The technique for measuring head circumference is described in Chapter 7. Be sure to check the measurement at least once to be certain it is accurate.

Large and Small Heads

Key Point

By far the most common cause of an unusually large head in an otherwise normal child is having a parent who also has a large head—most often the father. If the father is not present, ask the mother if he has trouble finding a hat that fits him.

When a child’s head circumference is two standard deviations or more above the mean, apply a tape measure to each of the parents’ heads to see where their measurements fit on the chart before creating anxiety or considering further investigation. Once it has been established that having a large head is a familial characteristic and that the affected parent and child are both otherwise normal, no further investigation is necessary. This normal variant goes by the pretentious name benign familial megalencephaly.

Occasionally, below-normal head circumference also is familial and benign (i.e., without associated developmental problems). More often, it is associated with developmental delay, even when it is familial. The usual cause of poor cranial growth is poor brain growth. Much less commonly, poor cranial growth can result from premature fusion of several cranial sutures (a condition known as premature synostosis). If all cranial sutures fuse prematurely, the head circumference will be small and the child eventually may show signs of increased intracranial pressure, such as papilledema and radiographic evidence of increased pressure by the cerebral gyri on the inner table of the skull—an exaggeration of the so-called digital impressions. This condition is quite rare.

More often, premature synostosis involves a single suture or a pair of sutures. This condition may be clinically recognized in two ways:

1. An elevated bony ridge is often palpable along the length of the fused suture.

2. The cranial shape will be distorted in a predictable, recognizable way, depending on which sutures have closed prematurely.

Remember that skull bones grow in a direction perpendicular to the suture lines. The directions in which the skull can and cannot grow after synostosis of a suture are therefore predictable, as is the shape of the resulting cranial distortion. For example, if the sagittal suture fuses prematurely, further lateral growth of the skull is prevented. Anteroposterior growth continues (perpendicular to the coronal sutures), and the skull will become long and narrow (a condition known as dolichocephaly) (Fig. 3-3).

FIGURE 3-3 A, Distortion of skull growth caused by premature synostosis (fusion) of coronal sutures. B, Distortion of skull growth caused by premature synostosis of sagittal suture (dolichocephaly).

Graphic recording of measurements

The child’s recumbent length or standing height, body weight, and head circumference should be recorded and plotted on appropriate age- and sex-specific growth charts. In North America, the growth charts currently used almost universally are those published in 2000 by the National Center for Health Statistics in collaboration with the National Center for Chronic Disease Prevention and Health Promotion (Fig. 3-4). These charts permit plotting of length-for-age, weight-for-age, and head circumference–for-age measurements along percentile lines, as well as plotting of body mass index (BMI) on a percentile chart.*

FIGURE 3-4 Growth charts for children from birth to 20 years.

A through D, Sex-specific growth charts for infants (birth to 36 months): length-for-age and weight-for-age percentiles (A and B), and head circumference-for-age and weight-for-length percentiles (C and D). E–H, Sex-specific growth charts for older children (2 to 20 years): stature-for-age and weight-for-age percentiles (E and F), and body mass index-for-age percentiles (G and H).

(Developed by the National Center for Health Statistics in collaboration with the National Center for Chronic Disease Prevention and Health Promotion, 2000; available at http://www.cdc.gov/growthcharts.)

BMI is determined using the following formula:

Arm span and its relationships

If a child is old enough to cooperate, you can measure the arm span by having the youngster stand with the back and heels touching the wall and the arms fully extended parallel to the floor, with the palms facing forward. With parental assistance and using a steel tape measure, measure the distance between the third fingers of each hand. The span-height difference and span-to-height ratio then can be determined (Fig. 3-5).

FIGURE 3-5 Measuring arm span. It is preferable to use a steel tape measure. Measure the distance between the tips of the third fingers.

Measuring the upper and lower segments

Measuring a child’s upper and lower segments is tricky and is not always supremely accurate. Obtaining these measurements requires identifying the top of the pubic ramus and marking it on the skin with a pen or wax pencil. This procedure sounds easier than it is, especially in a chubby youngster, in whom you must indent the adipose lower abdominal-suprapubic area to locate the top of the pubic bone. After you make the mark and release the pressure, the abdominal wall springs back and the mark does not always stay where you thought it was relative to the pubis. Make sure the youngster does not bend forward to look, because this movement can distort the measurement. Measure the lower segment by dropping a steel tape perpendicularly from the mark to the floor (Fig. 3-6, A). Then determine the length of the upper segment by subtracting the lower segment length from the height. Part B of Figure 3-6 shows the average upper-to-lower segment ratio at different ages. Remember that there are ethnic and familial differences in these ratios, so it is sometimes necessary to measure the parents as well.

FIGURE 3-6 A, Measuring the lower body segment. Subtract this measurement from the standing height to obtain the upper body segment measurement. B, Upper-to-lower body segment ratio for males and females, birth to 16 years.

(B from Greene MG, editor: The Harriet Lane handbook, 12th ed, St. Louis, Mosby–Year Book, 1991.)

A Language for Communicating Information About Children’s Growth

From time to time, a child is described as being “below the third percentile for height and weight.” That popular style of description is an abomination and a curse. In the first place, by definition, 3% of the normal population rightfully belongs below the third percentile of any growth parameter. This placement does not automatically categorize them as abnormal. Also, such phrasing tells us absolutely nothing about (1) how far below the third percentile the measurements fall and (2) whether the child’s linear and ponderal growth are impaired proportionally or disproportionally.

Several ways of expressing growth measurements are more meaningful and useful. One is to determine the child’s “height-age” or “weight-age” (i.e., the age for which a particular measurement represents the 50th percentile on a standard growth chart) (Fig. 3-7). Figure 3-7 shows that the boy in question, whose chronologic age is 10 years 4 months, has a height-age of 7 years and a weight-age of 5 years 2 months. Stating each measurement in these terms immediately communicates the image of a child who is a little shorter than average but is also underweight or undernourished, even in relation to his reduced height.

FIGURE 3-7 Determination of height-age, weight-age, and ideal weight for (actual) height.

Weight As a Percentage of Ideal

A useful way to express the ponderal aspect of a child’s nutritional status is weight as a percentage of ideal. Ideal, in this case, means the ideal (average) weight for the child’s actual recumbent length or standing height. This value is simple to determine, as illustrated in Figure 3-7. The boy’s height is 120 cm. Extrapolating horizontally to the 50th percentile shows that he has a height-age of 7 years. If you drop a perpendicular line to the weight graph from his height-age until it meets the 50th percentile weight line, you see that the ideal weight for his actual height is approximately 23.5 kg.

You can express his actual weight as a percent of ideal as shown in the following equation:

Table 3-1 shows the classification of protein-energy malnutrition according to McLaren and Read’s arbitrary system. This system of expression conveys an immediate and vivid image of the severity of a child’s undernutrition, irrespective of the underlying cause.

TABLE 3-1 Classification of Protein-Energy Malnutrition

From McLaren DS, Read WC: Classification of nutritional status in early childhood, Lancet 2:146, 1972.

Children With Delayed Growth

There are many causes of growth delay; those due to growth hormone or thyroxine deficiency are discussed in Chapter 16.

In children with constitutional growth delay, bone maturation is typically delayed (i.e., bone age is significantly less than chronologic age), and frequently one of the parents has a history of similar linear growth and pubertal delay.

Anxieties of the Short Child

The boy with constitutional growth and pubertal delay, whose classmates seem to tower over him, often fantasizes that he is destined to remain forever frozen in stature at his current height and in his hairless, undersized, microgenital state. For such a youngster, vague reassurance that he will “probably” attain normal height offers cold comfort at best. By contrast, giving him and his parents a reliable prediction of his adult height will immediately improve his self-image and his vision of the future. Furthermore, if you use either an orchidometer or a centimeter rule and determine that the testes have begun to enlarge beyond the usual prepubertal volume of approximately 1 mL, you can state unequivocally, despite the absence of adult sweat odor or of pubic or axillary hair, that the miracle of puberty is already underway and that further exciting developments are imminent.

Predicting Ultimate Adult Height

Several methods are available for predicting adult height in children who have no underlying skeletal abnormality, endocrinopathy, or other disease. The technique developed by Roche and colleagues (named the RWT method, after its authors) is one of the most accurate, simple, and practical methods available.

The original RWT method required only a knowledge of the child’s age, weight, height, bone age (as determined from a radiograph of one wrist and comparison with normal standards), and the mid-parental stature (i.e., the sum of mother’s and father’s heights divided by 2). Each measure was then multiplied by a positive or negative weighting factor derived from the calculated mathematical contribution of each to the determination of final adult height. The sum of values of the positive products minus the sum of values of the negative products yields the predicted adult height in centimeters. The original article describing this method provides the necessary tables and instructions to do this simple calculation, which takes only a few moments, especially if you use a calculator.

The most recent modification of the RWT method, known as the Khamis-Roche method, does not require the determination of skeletal age and has only marginally less accuracy and reliability than the original method.

Growth (Height) Velocity

For children who have significant disturbances of growth, for those receiving treatments that may impair growth, and for those being treated for growth disturbances, measurement of growth velocity can provide far more meaningful information than static measurements of height and weight. Tanner and Davies have pointed out that once puberty has begun, the use of cross-section population curves to plot the growth of children is misleading because, for example, the course of the 50th percentile line is not always followed by individual children. If a child happens to be an early or late maturer, the deviation is particularly marked. The growth velocity charts devised by Tanner and Davies include standard curves for early and late maturers (Fig. 3-8). When you use this system to record height velocity, remember that the height increments on which the charts are based are whole-year increments.

FIGURE 3-8 Growth velocity charts for North American girls (A) and boys (B).

(From Tanner JM, Davies PS: Clinical longitudinal standards for height velocity for North American children, J Pediatr 107:317, 1985.)

Like trees, children grow faster in the spring and summer and slower in the fall and winter. Therefore, height measurements used to determine growth velocity should be made at no less than approximately 1-year intervals.

Staging Pubertal Development

In normal children and in children with any disorder of secondary sexual development, the stage of puberty must be defined as precisely as possible whenever a physical examination is performed. Generalizations such as “early breast development,” “scant pubic hair,” and “prepubertal testes” are too vague and imprecise for documenting the progression of normal or abnormal secondary sexual development with the required accuracy, especially when the interval between consecutive examinations may be months or years, and memory for such details cannot be trusted.

Tanner and Davies divided the process of breast and pubic hair development into stages, as outlined in Figure 3-9. Their system of staging these elements of pubertal development is now used worldwide. In most girls, breast budding is the earliest physical manifestation of puberty, although in some perfectly normal girls, adrenarche (pubic and axillary hair development) may precede thelarche (breast development). The idea that girls enter puberty much earlier than boys has been somewhat overstated, simply because the physical manifestations of the onset of puberty are more obvious in girls. On average, girls show their earliest secondary sexual changes only about 6 months ahead of the earliest manifestations in boys. The first pubertal change in most girls takes the form of breast budding. In boys, however, the typical earliest evidence of secondary sexual development is testicular enlargement. Thus, unless you make it a regular practice to use an orchidometer or other means to measure the size of testes, you can easily miss a 1- or 2-mL increase in testicular volume between visits, whereas you would rarely miss a newly evident breast nodule.

FIGURE 3-9 Tanner stages of breast and pubic hair development in boys (A) and girls (B).

(From Johnson TR, Moore WM, Jeffries JE: Children Are different: physiology, 2nd ed. Columbus, Ohio, Ross Laboratories, 1978.)

Parents who discover a unilateral “breast lump” (i.e., a firm tender nodule under the areola) in their 8-year-old daughter, sometimes begin to worry that the child may have cancer. No physician should ever fall in with such a suspicion or think of performing a biopsy of such a nodule, which represents the child’s entire endowment of breast tissue. Breast malignancy is, for practical purposes, unknown in children.

Dental Development

Children vary considerably in the ages at which their teeth erupt, depending partly on genetic factors. Table 3-2 summarizes the average ages for calcification and eruption of primary and secondary dentition and, for primary dentition, the usual ages of tooth shedding.

Nutritional Assessment

A child’s height and weight and his or her weight-to-height relationship remain the best general guides to overall nutritional status with respect to protein-calorie sufficiency.

Today, with the exception of iron deficiency (with or without associated anemia), deficiencies of specific nutrients due to inadequate intake are relatively rare in developed countries. Nutritional rickets (vitamin D deficiency) virtually disappeared after the introduction of legal requirements to supplement cow’s milk with vitamin D. Similarly, universal supplementation of infant formula products with vitamin C eliminated scurvy from the clinical scene. By far the most common clinical nutritional disorders are protein-calorie malnutrition, resulting either from disease or psychosocial deprivation, and nutritional iron deficiency. Other specific nutrient deficiencies are more likely to be associated with particular diseases; examples are deficiencies of fat-soluble vitamins in persons with steatorrhea and of vitamin B₁₂ in persons with chronic ileal disease.

Clinical Assessment of the Child With Possible Iron Deficiency

Evaluating the Obese Child

Despite a huge and growing volume of literature on obesity, the prevalence of which is often referred to as an “epidemic,” the volume of such publications is almost inversely proportional to our level of success in preventing or treating the condition. First, although the literature on obesity often seems to imply that we are dealing with a unitary condition, we know that this is not the case. It is simplistic and unhelpful to regard obesity simply as an energy imbalance between intake and output. It has been said that the idea that obesity is caused by eating too much is about as helpful as the notion that alcoholism is caused by drinking too much. Many societal factors have contributed to the well-recognized decline in children’s average energy output in developed countries, such as shorter distances from home to school, use of buses and automobiles, urban environments that are unsafe for walking, and electronic factors (e.g., television, video games, MP3 players, and other gadgetry).

Our society’s bias against obesity and worship of thinness as the ideal human form undoubtedly magnifies the discomfiture and low self-esteem of obese children. The first step in trying to be genuinely helpful to an obese child is to search your own soul and ask yourself how you really feel about obese people. When I have asked groups of physicians to tell me, using only one word, how they feel when they are faced with an obese patient, the initial response is usually an embarrassed silence. After a few moments, the hesitant confessions begin, often as single adjectives—“frustrated,” “depressed,” “angry,” or even “disgusted.” A medical degree confers no immunity against societal biases. Feelings of frustration among health professionals are also understandable, because with only a few exceptions, most long-term results of attempts to achieve sustained weight loss in obese children and adults have been disappointing. To some extent, such frustration results from trying to treat the obesity rather than attempting to help the child who happens to be obese. How you begin the interview and the tenor and content of your conversation therefore are critical.

It is a good idea for your first words to the youngster to consist of a compliment on any handy topic, such as clothing or good looks. You should follow the compliment with the statement that you are glad to see the child. It also helps to verbalize your recognition that the child may be unhappy about coming to see you but that you would like to try to help him or her anyway.

Take great care not to reinforce, by verbal or nonverbal slips, the poor self-image that is almost universal among obese children. Even parents of an obese child, who often are obese themselves, may inadvertently contribute to this negativism, perhaps because they recall the unhappiness they experienced growing up obese. They may see themselves reflected in the child and may not like what they see.

Physical examination of the obese child

Key Point

Do not begin the physical examination of an obese child by putting the child on the scale!

Most prepubertal children with obesity that cannot be ascribed to a specific syndrome or endocrine disturbance—in other words, the majority of obese children—tend to be taller than average for their genetic endowment. The obese child who is short for his or her age deserves a closer look for a specific cause.

A useful way to begin is by examining the child’s hands and feet. In obese children, always check the area of skin over the base of the fifth finger and fifth toe. The presence of a small stellate scar is a telltale sign that a skin tag was removed soon after birth with a suture tied tightly around it (Fig. 3-10). In fact, such a skin tag was almost certainly a rudimentary supernumerary digit. This finding, coupled with obesity, raises the likelihood that the child has Laurence-Moon-Biedl syndrome, in which obesity is often associated with polydactyly, retinitis pigmentosa, progressive loss of vision, some developmental delay, and, often, a progressive nephropathy.

FIGURE 3-10 A barely visible stellate scar at the base of the fifth finger is the sole evidence of a “skin tag” (actually a rudimentary supernumerary digit) that was tied off in the newborn period. This finding is an important clue to the cause of this child’s obesity, which is Laurence-Moon-Biedl syndrome.

Another uncommon but important sign to look for in the hands of obese children is the metacarpal sign. Children with pseudohypoparathyroidism (a syndrome associated with obesity) often have strikingly short fourth and fifth metacarpals and metatarsals. Elicit the metacarpal sign by having the youngster make a fist. When the fourth and fifth metacarpals are hypoplastic, the relevant knuckles are absent and are often replaced by dimples (Fig. 3-11). Incidentally, this sign also is seen in girls with Turner syndrome (XO anomaly).

FIGURE 3-11 The “metacarpal sign” (unusually short fourth and fifth metacarpals) seen in pseudohypoparathyroidism and in Turner syndrome. A, No fourth and fifth knuckles are seen when the child makes a fist. B, Extension of the fingers shows unusually short fourth and fifth fingers due to hypoplasia of the metacarpals.

Stretch marks often are observed in the skin of the abdomen and thighs of obese children. (See Chapter 16 for the distinction between Cushing syndrome and obesity of other causes.)

Another obesity syndrome that usually can be suspected simply from the history and physical findings is Prader-Willi syndrome. In affected children, obesity typically develops between 6 months and 6 years of age and usually is associated with mild to moderate developmental delay, hypotonia, and feeding problems in infancy. The facies is characteristic, with a prominent forehead and rather almond-shaped eyes. The hands and feet are small. Compulsive overeating usually appears by 3 years of age. In boys, the penis and scrotum are often small, and in girls, the labia is poorly formed. The syndrome is usually caused by a defect in the paternal chromosome 15.

Evaluating the Child With Failure to Thrive

The central issue in a child with failure to thrive is usually whether the child’s nutritional or growth deficiency is due to underlying (unrecognized) organic disease or to some form of psychosocial deprivation. As with other growth disturbances, the history, physical examination, and observation of the child’s behavior and the family interaction are by far the most powerful diagnostic tools.

When there are no clear-cut signs suggesting organic disease, a complete psychosocial history and direct observation of the child and family (as described in Chapter 1) usually allow a diagnosis of deprivational growth failure and malnutrition to be made on distinct positive grounds rather than by exclusion.

Summary

Accurate measurements over time and comparisons with established standards are essential for the early recognition, diagnostic evaluation, and successful management of growth and nutritional problems in infants and children. In evaluating children with suspected growth problems, always ask yourself first, “Is the child normal?” The concepts of height-age, weight-age, and weight as a percentage of ideal provide useful, meaningful, and accurate expressions for communicating information about children’s growth. The trajectory and outcome of every child’s growth must always be considered in relation to those of the parents.

The myth that teething can explain signs and symptoms in infants should be abandoned once and for all.

An understanding of the special anxieties of the short child, the obese child, and the child with delayed puberty should dictate the style and content of the history interview and the physical examination. For children with a constitutional delay of growth and puberty, calculating the predicted adult height is as valuable therapeutically as it is diagnostically.

For the obese child, understanding the central role of heredity and appreciating how obesity colors and complicates the child’s life allows you and the family to focus on potentially remediable problems rather than reinforcing everyone’s belief in the impossible dream that thinness is the sole path to health and happiness.

At the other nutritional extreme, when a child fails to thrive, a truly thorough history and physical examination, coupled with observation of family interaction, rarely leave much doubt as to whether the child’s problem is rooted in organic disease or in psychosocial deprivation. In either instance, the distinction is based on positive findings, not on exclusion.

Protein-calorie malnutrition and iron deficiency are by far the most common nutritional abnormalities encountered in North American children. In children with iron deficiency, the history of prolonged bottle-feeding and the child’s consumption of most of his or her energy requirement in the form of milk are key to understanding the pathogenesis of this condition and designing a successful management program.