Growth charts
Growth charts are graphical tools used to assess and monitor the growth and development of children, typically from infancy to adolescence. They display a range of measurements, including height, weight, and head circumference, allowing healthcare professionals to compare an individual child's growth against established percentiles for their age and gender. These charts help identify whether a child's growth patterns are within a normal range or if further evaluation is needed, particularly when measurements fall below the 5th percentile or above the 95th percentile.
Originating from extensive body measurement data collected from large groups of children, growth charts provide benchmarks that reflect population standards. In the U.S., the current growth charts, developed in 2000 by the Centers for Disease Control and Prevention (CDC), have been a staple for tracking children's physical development. They include various curves, enabling healthcare providers to plot a child's measurements and determine their percentile ranking. This percentile system helps in understanding growth trends and may indicate potential health issues, guiding appropriate interventions if necessary.
Growth charts
Summary: Children’s development both mentally and physically is modeled using data-based norms, some of which are indicated by growth charts. .
When a parent brings his or her child to a physician for a checkup, a number of measurements are taken to help the physician assess the health and development of the child. For children up to 36 months of age, three typical measurements include height, weight, and head circumference. The healthcare professional will use these measurements to decide whether the child is on track developmentally. These measurements are expected to vary depending on the gender and age of the child. Considering weight, for instance, younger children tend to weigh less than older children and girls tend to weigh less than boys. However, there is even considerable variability in these measurements for children within the same gender and age group. There are individual differences from child to child resulting from genetic and environmental factors, including diet and physical activity habits.
Percentiles
To make a judgment about whether the child’s development is on track, the relevant question to pose is where the child’s measurements fit in relation to other children of the same age and gender in the population. Percentiles are typically used to facilitate this comparison and growth charts summarize these quantities in graphs. If a young boy’s weight is at the 75th percentile, this means that of the boys the same age in the population, about 75% of them weigh less and about 25% of them weigh more than this boy. If parents are told that one of their child’s measurements is at the 99th percentile, should they be concerned? Very high or very low percentiles may be a sign of something abnormal. For example, a child’s weight at the 4th percentile may be a sign of malnutrition. Extreme measurements indicate to the healthcare professional that further follow-up may be necessary. Generally speaking, measurements under the 5th percentile or over 95th percentile or growth patterns that shift considerably in terms of their percentiles over time require further assessment.
Growth Charts
Growth charts are graphical summaries of mathematical functions that are developed based on extensive body measurement data collected on large groups of children from the population of interest. They provide benchmarks for comparison and are widely used by the health community to monitor and track the growth and development of children. According to the Centers for Disease Control and Prevention (CDC), growth charts have been used in the United States since 1977. Prior to 1977, there were child development references in use, but they did not adequately represent the population. As of 2011, the charts used in the United States are the 2000 CDC Growth Charts. The infant (0–36 months of age) charts include smoothed percentile curves of weight by age, length by age, head circumference by age, and weight by length for boys and girls. The children and adolescent (2–20 years of age) charts include weight by stature, weight by age, stature by age, and body mass index by age for each sex.
In order to find a percentile based on these charts, one needs to be able to plot a point on the graph. For instance, consider the weight-by-age infant chart for boys. Suppose the boy is 18 months and his weight is 25 pounds. Find 18 months along the horizontal axis and 25 pounds along the vertical axis of the graph. Mark this point. Based on the chart, this point falls between the 25th and 50th percentile curves. As demonstrated by this example, not all percentile curves are summarized in the charts. If a measurement falls somewhere between the 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, or 97th percentile curve, the professional reading the chart will need to interpolate between curves to approximate the percentile value.
The percentile curves summarized in the 2000 CDC Growth Charts were developed by the United States National Center for Health Statistics (NCHS) based on the results from a number of large health surveys conducted based on representative groups from the U.S. population. Data analysis was used to estimate percentiles for the various growth measurements and statistical modeling was used to smooth the estimates into the percentile curves to facilitate comparisons.
Bibliography
Kuczmarski, R. J., C. L. Ogden, and S. S. Guo, et al. “2000 CDC Growth Charts for the United States: Methods and Development.” National Center for Health Statistics. Vital and Health Statistics 11, no. 246 (2002).
World Health Organization (WHO). “The WHO Child Growth Standards.” http://www.who.int/childgrowth/standards/en.