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.

Weight

Infants and young children should be weighed naked or wearing a diaper at most, with the weight of the diaper subtracted afterward. The scales should be reliable and should be checked for accuracy and balance before each use. In hospitalized children, weight fluctuations often influence management. Therefore, infants should be weighed at the same time each day, ideally in the morning before being fed and, if possible, always by the same caregiver. Any unusual or unexpected fluctuation calls for reweighing. If a sudden gain or loss of weight is validated, a reasonable explanation (e.g., edema causing a sudden gain or inadequate intake, diuresis, or diarrhea causing a sudden loss) should be sought.

Occasionally, young children resist sitting or standing alone on a scale to be weighed. When that happens, rather than struggling to attain dubious success, have a parent stand on the scale while holding the child in his or her arms. Then weigh the parent alone and determine the child’s weight by subtraction.

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:

Mid-parental height

Because the growth potential of a child depends on genetic factors, calculation of the mid-parental height (also referred to as target height) is very useful. Measure the parents yourself if possible. Take the sum of the parents’ heights, add or subtract 13 cm for boys or girls, respectively, and divide by 2 to get the mid-parental height. The child’s growth would be expected to be tracking to an adult height that is within two standard deviations or ±9 cm of this number. Often, showing parents that the child’s growth fits with the family pattern will allay their concerns about their child’s height.

Special growth charts have been developed for children with certain dysmorphic conditions, including Down syndrome, Turner syndrome, and achondroplasia (see Recommended Reading).

Proportion and disproportion

When a child seems unusually short, first determine whether the growth retardation is proportional or disproportional—that is, whether there is significant disproportion between the growth of the head, trunk, and extremities. The chondrodysplasias, of which the best recognized is achondroplasia, are characterized by shortening of the limbs with normal linear growth of the trunk. Thus the achondroplastic child (terms such as dwarf and midget should never be used, because they have very disturbing connotations for parents) has a normal sitting height but a markedly reduced standing height.

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.)

Importance of sequential measurements

When growth deviates from normal standards, sequential measurements over significant periods are needed to evaluate the underlying problem adequately and, when necessary, to monitor the response to treatment. The older the child, the longer the measurement interval that is required to assess the significance of any apparent deviation in growth. Measurement of growth velocity, as described later in this chapter, can be more informative than “snapshot” anthropometric measurements taken at a particular moment in time.

Regular charting of height and weight should be part of every child’s routine health care. Parents should be encouraged to keep their own records of these measurements. During the first year of life, it is not unusual for a child’s height and weight measurements to cross at least one percentile line. After 18 months to 2 years of age, however, measurements in most healthy children tend to stay within the same percentile channel (or an adjacent channel) until the onset of puberty, unless obesity develops or some form of significant growth delay occurs.

Once normal head circumference has been established in infancy, it is usually unnecessary to continue measuring the head circumference regularly unless this is specifically indicated (e.g., by the presence of a neurologic or developmental problem).

Useful as they are, growth charts are no substitute for good judgment. Children march to individual drummers and often follow the growth timetables and growth trajectories of their antecedents. Remember that the curves on published growth charts are smoothed-out representations of observations of many healthy youngsters. Individual children, not having read this textbook, may not follow such idealized curves precisely, because their growth may occur in irregular spurts.

When you find any deviation from these “normal” curves, ask yourself what that deviation actually means in terms of the child’s genetic, medical, and psychosocial history and current health status. Whenever possible, use growth charts derived from the same geographic area or ethnic population as that of the child under consideration. For example, many Southeast Asian children have heights and weights below the third percentiles of North American growth charts. These differences may reflect a mixture of ethnic (genetic) and nutritional (environmental) factors. When the economy of a region improves dramatically over a few years, average heights and weights of children can increase remarkably. In fact, average height for age in a particular population over time is a telling measure of the health of a nation’s economy.