Background
Length
Weight
Head Circumference
The term anthropometric refers to comparative measurements of the human body. The anthropometric measurements commonly used as indices of growth and development for infants include length, weight, and head circumference. Typically, growth is evaluated by comparing individual measurements to reference standards, represented by percentile curves on a growth chart. In assessing and monitoring the nutritional status of a low birth weight infant it is most helpful to evaluate a pattern of measurements obtained on a regular basis over time. For anthropometric measurements to be valid indices of growth status, they must be highly accurate, requiring precision in measuring technique. Accurately measuring children with physical abnormalities is often a challenge.
Equipment:
Use a length-measuring device with a fixed headboard and a moveable footboard that are perpendicular to the surface on which the child is lying. A fixed measuring tape, marked in millimeters or in 1/16 in. segments, should be attached to the surface with the zero end at the edge of the headboard. Several commercial versions of length boards are available.
Technique:
Two people are required to measure length accurately:
Person A
1. Hold the head with crown against the headboard so that the child is looking straight upward.
2. Make sure the trunk and pelvis are properly aligned with the measuring device.
Person B
1. Straighten the child's legs and hold the ankles together with the toes pointed directly upward.
2. Move the footboard firmly against the soles of the feet.
3. Read the measurement to the nearest 0.1 cm (1/8 in).
4. Repeat the measurement until two measurements agree within 0.2 cm (1/4 in).
5. Record the numerical value and plot length for age on the appropriate growth chart.
6. If the child is uncooperative and you cannot get an accurate measurement, record your best estimate on the growth chart and note the circumstances of the measurement.
Equipment:
Use a beam scale with non-detachable weights or an equally accurate electronic scale. For infants and young children who are weighed lying down use a pan-type pediatric scale that is accurate to within 10 gram or 1/2 oz. Do not use spring-type bathroom scales; with repeated use, they may not maintain the necessary degree of accuracy.
Frequently check and adjust the zero weight on the beam scale by placing the main and fractional sliding weights at their respective zeros and moving the zeroing weight until the beam is in balance at zero. If a pad or diaper is used to make the pan more comfortable, place it in the pan when the zero adjustment is made; otherwise the weight of the pad or the diaper must be subtracted from the weight of the child each time a measurement is made. Whichever method is used to account for the weight of the diaper or pad, note it on the growth chart. At least two or three times per year, have the accuracy of the scale checked with a set of standard weights by a local dealer or inspector of weights and measures.
Technique:
2. Read the measurement to the nearest 10 gram or 1/2 oz.
3. Repeat the measurement two to three times and, after excluding those that are obviously wrong, average the values.
4. Record the numerical value on the growth chart and plot weight for age and weight for length on the appropriate growth chart(s) Note: It's not always possible to plot weight for length on small infants with lengths below 55 cm.
5. If the infant moves excessively, an accurate measurement is unlikely; postpone the measurement for a few minutes.
6. If the infant still does not keep still, skip the measurement unless you can make a reasonable estimate. If the weight you record on the growth chart is an estimate, note the circumstances on the growth chart.
Head Circumference Measurement
The measurement of head circumference is an important screening procedure for detecting abnormalities of head growth. Although usually caused by non-nutritional factors, slow head growth can be a result of severe under nutrition. Children with poor head growth frequently have poor linear growth as well. Thus knowledge of head size is very important in assessing possible nutritional factors contributing to short length or stature. Head circumference should be measured routinely until at least 36 months of age.
Equipment:
Use a flexible, nonstretchable measuring tape.
Technique:
2. Place the lower edge of the measuring tape just above the child's eyebrows, above the ears and around the occipital prominence at the back of the head.
3. Pull the tape snugly to compress the hair. The objective is to measure the maximal head circumference.
4. Repeat the measurement twice or until two measurements agree to 0.1 cm (1/8 in).
5. Record the numerical value immediately and plot on the growth chart.
6. If the measurement appears abnormal when plotted, check the accuracy of plotting and recheck the measurement.
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