How is length measured for an infant or child under 2 years of age?
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In pediatrics, the essential growth measurements in infants and toddlers to age 2 years are length, weight, head circumference, and weight-for-length. For children ages 3 years and up, the essential measurements are height, weight, and body mass index (BMI). Show
Measurement of growth in infants and toddlersThe measurement of length in children 2 years and younger is most accurate when 2 people can assist: one to position the child and one to measure. The child should be placed supine on a measuring board, and the measurement should be reported to the nearest 0.1 cm (see the image below). Measurement of weight in this population should be taken on a scale that has been properly calibrated. The infant/ toddler should be weighed without clothing or diaper, and the measurement reported to the nearest 0.1 kg. The ratio of weight-to-length is used to predict adiposity in children under the age of 2, rather than BMI. This measurement can also be plotted on a standardized growth chart.  View Media Gallery Head circumference is measured in children up to age 3, as this is the time of greatest brain growth. It is correctly measured using a flexible tape measure at the maximum diameter through the supraorbital ridge to the occiput. The value should be reported to the nearest 0.01 cm and plotted on a standardized growth chart. [1] Of note, head circumference should also be measured in older children with abnormal weight and height measurements, as it may provide insight into the underlying cause. Abnormal head growth is classified as either macrocephaly, greater than 2 standard deviations above the mean, or microcephaly, greater than 2 standard deviations below the mean. [5, 6] View Media Gallery Measurement of growth in older childrenIn children over the age of 2, height, weight and body mass index (BMI) are commonly measured (see image below). As noted in the previous section, head circumference may still be measured between the ages of 2-3 years. In children older than 2 years, standing height rather than recumbent length is measured. The measurement should be performed without shoes using a stadiometer. The mean of 3 measurements should be taken to ensure the greatest accuracy, and it should be plotted on a standardized growth curve. View Media Gallery Of note, length is about 1 cm greater than standing height. Height velocity can also be measured by looking at the centimeters grown in a year (cm/yr) and can be plotted on a standardized curve; [7] it is valuable in detecting growth abnormalities early in the course of chronic illness. Weight should be measured without shoes and little/no outer clothing. It should be reported to the nearest 0.1 kg and plotted on a standardized growth curve. Body mass index is derived from the measurements of height and weight and shows the relative proportion between the 2; it is a valid predictor of adiposity. [8] BMI will vary based on gender, age, and pubertal stage. The calculation for BMI is as follows:
BMI has been recommended as the most appropriate single indicator of an overweight patient and obesity in the pediatric population in the clinical setting. The measurements required to calculate BMI are done routinely at pediatric health maintenance visits and are noninvasive, inexpensive, and easily understood. [2] BMI values are then to be plotted on a BMI reference chart; a child with a BMI greater than the 85th percentile is overweight, and a child with a BMI greater than the 95th percentile is obese. Children with a BMI less than the 5th percentile are considered underweight. Other methods can be used to measure adiposity more directly. These include measurements of the triceps and subscapular skinfolds (see the images below). However, skinfold measurements can be difficult to obtain in the outpatient clinical setting. A recent study showed that, for children 5-18 years of age, BMI-for-age, triceps skinfold-for-age, and subscapular skinfold-for-age individually all performed equally well in the classification of excess body fat. [9] View Media Gallery View Media Gallery Other measurements of growth in pediatricsBody proportions At birth, the head and trunk are large relative to the rest of the body. The limbs continue to lengthen during the course of development, especially during puberty. This can be quantified by obtaining upper body segment and lower body segment measurements. The lower body segment is the measurement of the length from the pubic symphysis to the floor; the upper body segment is the height minus the lower body segment. The U/L ratio (upper body segment : lower body segment) at birth is about 1.7; at age 3 years it is 1.3; at greater than 7 years, it is 1.0 with the upper body segment and lower body segment being about equal. Of note, higher U/L ratios are noted in short-limb dwarfism and other bone disorders such as rickets. Skeletal maturation Bone age and stages of pubertal development are closely correlated and can be helpful in predicting adult height in early or late-developing adolescents. Skeletal maturity is more closely linked to sexual maturity than it is to chronological age. Dental development The sequence of events in dental development includes mineralization, eruption, and exfoliation. Mineralization can begin as early as the 14th week of gestation and continues until approximately age 3 years for the primary teeth. Tooth eruption begins with the central incisors and continues laterally. Delayed tooth eruption is classified by the absence of any teeth by 13 months of age; possible causes of this include hypothyroidism, hypoparathyroidism, or idiopathic delayed eruption (most common). Exfoliation begins around 6 years of age and continues until around age 12 years. Some causes of early exfoliation to consider are histiocytosis X, cyclic neutropenia, leukemia, trauma or idiopathic causes. [1]
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