- Click here for explanation of classification scheme.

The purpose of this report is to provide detailed information on how the 2000 Centers for Disease Control and Prevention (CDC) growth charts for the United States were developed, expanding upon the report that accompanied the initial release of the charts in 2000.

• Growth charts for the United States were developed by NCHS when nationally representative cross-sectional survey data became available for most of the pediatric age range
• Data from the National Health Examination Survey (NHES) II (1963-1965) for ages six to 11 years, NHES III (1966-1970) for ages 12 to 17 years, and the first National Health and Nutrition Examination Survey (NHANES) I (1971-1974) for ages one to 17 years were used to develop these charts
• National survey data were not available for the period from birth to one year
• Children ages six to 11 years from NHES II, 12 to 17 years from National Health and Nutrition Examination Survey (NHANES) III, one to 19 years from NHANES I, six months to 19 years from NHANES II, and two months to 19 years from NHANES III were included in the revision
• The small number of children in NHES II who had their 12th birthday after the home interview and before the examination and those who had their 18th birthday after the home interview and before the examination in NHES III were also included.

• Data for all very low birth weight (VLBW) infants (less than 1,500g) were excluded from the infant growth charts, primarily because the growth of VLBW infants is known to be markedly different from that of higher birth weight, full-term infants
• For NHANES III, if a reported birth weight was missing from the survey interview data, birth weight from the child's birth certificate was used to determine possible exclusion and if neither were available, an exclusion was not made
• Data from NHANES II for children greater than or equal to six years of age were excluded from the charts for weight-for-age, weight-for stature and BMI for age
• Two outlier values, one for head circumference of an infant girl, and one for recumbent length of an infant boy, were excluded because the measurement values and the sampling weights were extreme.

Recruitment

• Data from the NHES II (1963-1965) for ages six to 11 years, NHES III (1966-1970) for ages 12 to 17 years, and the first NHANES I (1971-1974) for ages one to 17 years were used to develop these charts
• Children ages six to 11 years from NHES II, 12 to 17 years from NHES III, one to 19 years from NHANES I, six months to 19 years from NHANES II, and two months to 19 years from NHANES III were included in the revision.

Design

Consensus report.

Statistical Analysis

• Data from the national surveys were pooled because no single survey in the NHANES series had enough observations to construct growth charts
• Sample sizes from 400 to 500 are required to achieve precision of the empirical percentiles at the specific ages selected for the curve fitting
• Statistical procedures were applied to the observed data in two stages, first to generate initial smoothed curves for selected major percentiles and second to generate the parameters that were used to construct the final smoothed curves and additional percentiles
• The first stage is referred to as the curve smooth staging and the second stage as the transformation stage
• In the first stage, selected empirical percentiles were smoothed with a variety of parametric and nonparametric regression procedures. In the transformation stage, the smoothed curves were approximated using a modified LMS estimation procedure to provide the transformation parameters, lambda, mu and sigma (LMS).
• This resulted in the final percentile curves that closely matched the percentile curves smoothed in the first stage and allowed computation of additional percentiles and Z-scores.

Timing of Measurements

• Data from the NHES II (1963-1965) for ages six to 11 years, NHES III (1966-1970) for ages 12 to 17 years, and the first NHANES I (1971-1974) for ages one to 17 years were used to develop these charts
• Children ages six to 11 years from NHES II, 12 to 17 years from NHES III, one to 19 years from NHANES I, six months to 19 years from NHANES II and two months to 19 years from NHANES III were included in the revision.

Dependent Variables

Growth chart development:

• Smoothed percentile curves were developed in two stages
• In the first stage, selected empirical percentiles were smoothed with a variety of parametric and nonparametric procedures
• In the second stage, parameters were created to obtain the final curves additional percentiles and Z-scores
• The revised charts were evaluated using statistical and graphical measures.

Initial N

As provided by data.

Attrition (Final N)

As provided by data.

Age

• Children ages six to 11 years from NHES II
• 12 to 17 years from NHES III
• One to 19 years from NHANES I
• Six months to 19 years from NHANES II
• Two months to 19 years from NHANES III were included in the revision.

Ethnicity

As provided by data.

Other Relevant Demographics

Not reported.

Anthropometrics

Source of data for each growth chart:

• Weight-for-age was birth to 36 months
• Length-for-age was birth to 36 months
• Head circumference-for-age was birth to 36 months
• Weight-for-length was 45 to 103cm
• Weight-for-stature was 77 to 121cm
• Weight-for-age was 24 to 240 months
• Stature-for-age was 24 to 240 months
• BMI-for-age was 24 to 240 months.

Location

United States.

Key Findings

• The 1977 National Center for Health Statistics (NCHS) growth charts were revised for infants (birth to 36 months) and older children (two to 20 years)
• New body mass index for-age (BMI for age) charts were created
• Use of national data improved the transition from the infant charts to those for older children
• The evaluation of the charts founds no large or systematic differences between the smoothed percentiles and the empirical data.

Major Features of the 2000 CDC Growth Charts for the United States

• National survey data: In the 2000 CDC charts, nationally representative survey data, supplemented with a limited amount of data from other sources, replaced the Fels data used in the 1977 NCHS infant growth charts from birth to 36 months
• BMI-for-age charts: New sex-specific BMI-for-age charts for two to 20 years were developed to replace the 1977 NCHS weight-for-stature charts that were applicable only at pre-pubescent ages for statures for boys ranging from 90cm to 145cm and for girls ranging from 90cm to 137cm. Revised weight-for-stature charts are available for optional use from ages two to five years. Either BMI-for-age or weight-for-stature charts may be used to assess risk of overweight from ages two to five years.
• Extended age range: The revised charts were extended by two years beyond the 1977 NCHS charts to include children and adolescents from two to 20 years of age. This change was made to accommodate adolescents who continue to be seen by pediatricians through their later teenage years.
• Additional percentiles: The third and 97th percentiles were added to each chart to facilitate plotting data for children at extremes of the distribution. The major percentiles included in the 1977 NCHS charts (fifth, 10th, 25th, 50th, 75th, 90th and 95th) were retained in the revised charts. The 85th percentile was added to weight-for-stature and BMI-for-age charts, enhancing their use as screening tools to identify children and adolescents who may be overweight or at risk of overweight.
• Corresponding percentiles and Z-scores: The 2000 CDC Growth Charts can be used to obtain percentiles and Z-scores. To meet the needs of researchers, for analyses of surveillance data and to monitor changes in growth indicators for individuals, Z-scores can be obtained and exact percentiles can be calculated.
• Smooth junction between length and stature: The revised charts largely correct discontinuities that existed in the 1977 charts for infants and older children from 24 to 36 months. These disjunctions were the result of using data from different sources.

• The 2000 CDC Growth Charts were developed with improved data and statistical procedures
• Health care providers now have an instrument for growth screening that better represents the racial ethnic diversity and combination of breast and formula feeding in the United States. It is recommended that these charts replace the 1977 NCHS charts when assessing the size and growth patterns of infants, children and adolescents.

Other:

National Center for Health Statistics, Maryland