May 2002 Series 11, Number 246 2000 CDC Growth Charts for the United States: Methods and Development Copyright information All material appearing in this report is in the public domain and may be reproduced or copied without permission; citation as to source, however, is appreciated Suggested Citation Kuczmarski RJ, Ogden CL, Guo SS, et al 2000 CDC growth charts for the United States: Methods and development National Center for Health Statistics Vital Health Stat 11(246) 2002 Library of Congress Cataloging-in-Publication Data 2000 CDC growth charts for the United States: methods and development p cm — (DHHS publication ; no (PHS) 2002-1696) (Vital and health statistics Series 11, Data from the National Health Survey ; no 246) ‘‘May, 2002.’’ ISBN 0-8406-0575-7 1 Children—Anthropometry—United States—Statistics 2 Children— United States—Growth—Statistics 3 United States—Statistics, Vital I Series II Series: Vital and health statistics Series 11, Data from the National Health Survey ; no 246 GN63 A225 2001 305.23'0973'021—dc21 2001051405 For sale by the U.S Government Printing Office Superintendent of Documents Mail Stop: SSOP Washington, DC 20402-9328 Printed on acid-free paper Series 11, Number 246 2000 CDC Growth Charts for the United States: Methods and Development Data From the National Health Examination Surveys and the National Health and Nutrition Examination Surveys DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Center for Health Statistics Hyattsville, Maryland May 2002 DHHS Publication No (PHS) 2002-1696 National Center for Health Statistics Edward J Sondik, Ph.D., Director Jack R Anderson, Deputy Director Jack R Anderson, Acting Associate Director for International Statistics Jennifer H Madans, Ph.D., Associate Director for Science Lawrence H Cox, Ph.D., Associate Director for Research and Methodology Jennifer H Madans, Ph.D., Acting Associate Director for Analysis, Epidemiology, and Health Promotion Edward L Hunter, Associate Director for Planning, Budget, and Legislation Jennifer H Madans, Ph.D., Acting Associate Director for Vital and Health Statistics Systems Douglas L Zinn, Acting Associate Director for Management Charles J Rothwell, Associate Director for Information Technology and Services Division of Health Examination Statistics Clifford L Johnson, M.S.P.H., Director Rosemarie Hirsch, M.D., M.P.H., Chief Analysis Branch Carolyn Petty-Martin, Acting Chief Operations Branch Vicki L Burt, Sc.M., R.N., Chief Planning Branch Lewis Berman, M.S., Chief Information Management Branch Acknowledgments W e wish to gratefully acknowledge the contributions of many individuals who had various roles in the growth chart revision process These contributions include statistical and computer programming expertise, data and summary statistics, graphical support, and knowledge and experience in the areas of pediatric growth and growth charts We also wish to thank Thelma Sanders and Zung Le for their editorial support In addition to acknowledging the contributions of all individuals identified in appendix I of this report, the following persons are also recognized, with their affiliations at the time of their contribution: Phil Batty Center for Health Information Management and Epidemiology State of Missouri Department of Health Jefferson City, MO Fred Buhr Center for Health Statistics State of Wisconsin Department of Health and Family Services Madison, WI Margaret Carroll National Center for Health Statistics Centers for Disease Control and Prevention Hyattsville, MD John Chang Computer Information Systems and Support Services Nova Research Company Bethesda, MD Chris Cronk Center for Health Statistics State of Wisconsin Department of Health and Family Services Madison, WI William Davis Klemm Analysis Group, Inc Washington, DC Catherine Duran National Center for Health Statistics Centers for Disease Control and Prevention Hyattsville, MD Odell Eldridge Computer Information Systems and Support Services Nova Research Company Bethesda, MD Stephen Sloan National Center for Health Statistics Centers for Disease Control and Prevention Hyattsville, MD Christine Zeller Department of Community Health Wright State University Yellow Springs, OH iii Contents Acknowledgments iii Abstract 1 Introduction Historical Background Concerns Surrounding the 1977 Charts The Revision 1 1 2 3 Methods Data Sources Data Exclusions Statistical Curve Smoothing Procedures 3 3 5 5 Results Observed and Smoothed Percentiles Evaluation of the Revised Growth Curves Differences Between the 1977 NCHS and the 2000 CDC Growth Curves 10 10 10 11 Discussion Revision Process Growth Chart Workshops Major Features of the 2000 CDC Growth Charts for the United States Using the Revised Growth Charts Specialized Charts General Growth Chart Principles 11 11 12 12 12 13 14 Conclusions 15 References 16 Appendix I Description of Growth Chart Workshops Workshop 1 Workshop 2 Workshop 3 Workshop 4 187 187 188 189 189 Appendix Table I Participants in the NCHS growth chart workshops 187 Figures 1 2 3 4 Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Boys weight-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Girls weight-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Boys length-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Girls length-for-age 19 20 21 22 v 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 vi Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Boys weight-for-length Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Girls weight-for-length Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Boys head circumference-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, birth to 36 months: Girls head circumference-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, 2 to 20 years: Boys weight-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, 2 to 20 years: Girls weight-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, 2 to 20 years: Boys stature-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles, 2 to 20 years: Girls stature-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th, 97th percentiles, 2 to 20 years: Boys body mass index-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th, 97th percentiles, 2 to 20 years: Girls body mass index-for-age Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th, 97th percentiles: Boys weight-for-stature Individual growth chart 3rd, 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th, 97th percentiles: Girls weight-for-stature Clinical growth chart 5th, 10th, 25th, 50th, 75th, 90th, 95th percentiles, birth to 36 months: Boys length-for-age and weight-for-age percentiles Clinical growth chart 5th, 10th, 25th, 50th, 75th, 90th, 95th percentiles, birth to 36 months: Girls length-for-age and weight-for-age percentiles Clinical growth chart 5th, 10th, 25th, 50th, 75th, 90th, 95th percentiles, birth to 36 months: Boys head circumference-for-age and weight-for-length Clinical growth chart 5th, 10th, 25th, 50th, 75th, 90th, 95th percentiles, birth to 36 months: Girls head circumference-for-age and weight-for-length Clinical growth chart 5th, 10th, 25th, 50th, 75th, 90th, 95th percentiles, 2 to 20 years: Boys stature-for-age and weight-for-age Clinical growth chart 5th, 10th, 25th, 50th, 75th, 90th, 95th percentiles, 2 to 20 years: Girls stature-for-age and weight-for-age Clinical growth chart 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th percentiles, 2 to 20 years: Boys body mass index-for-age Clinical growth chart 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th percentiles, 2 to 20 years: Girls body mass index-for-age Clinical growth chart 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th percentiles: Boys weight-for-stature Clinical growth chart 5th, 10th, 25th, 50th, 75th, 85th, 90th, 95th percentiles: Girls weight-for-stature Smoothed percentile curves, 22–39 months: Boys length-for-age and stature-for-age Smoothed percentile curves, 22–39 months: Girls length-for-age and stature-for-age Smoothed percentile curves, 75–106 cm: Boys weight-for-length and weight-for-stature Smoothed percentile curves, 75–106 cm: Girls weight-for-length and weight-for-stature Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, birth to 36 months: Boys weight-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, birth to 36 months: Boys weight-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, birth to 36 months: Girls weight-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, birth to 36 months: Girls weight-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, birth to 36 months: Boys recumbent length-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, birth to 36 months: Boys recumbent length-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, birth to 36 months: Girls recumbent length-for-age 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, birth to 36 months: Girls recumbent length-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 46–102 cm: Boys weight-for-length Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 46–102 cm: Boys weight-for-length Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 46–102 cm: Girls weight-for-length Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 46–102 cm: Girls weight-for-length Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, birth to 36 months: Boys head circumference-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, birth to 36 months: Boys head circumference-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, birth to 36 months: Girls head circumference-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, birth to 36 months: Girls head circumference-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 78–120 cm: Boys weight-for-stature Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 78–120 cm: Boys weight-for-stature Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 78–120 cm: Girls weight-for-stature Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 78–120 cm: Girls weight-for-stature Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 24–237 months: Boys weight-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 24–237 months: Boys weight-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 24–237 months: Girls weight-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 24–237 months: Girls weight-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 24–237 months: Boys stature-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 24–237 months: Boys stature-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 24–237 months: Girls stature-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 95th percentile curves to empirical data points, 24–237 months: Girls stature-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 24–237 months: Boys body mass index-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 85th, 95th percentile curves to empirical data points, 24–237 months: Boys body mass index-for-age Comparison of smoothed 3rd, 10th, 50th, 90th, 97th percentile curves to empirical data points, 24–237 months: Girls body mass index-for-age Comparison of smoothed 5th, 25th, 50th, 75th, 85th, 95th percentile curves to empirical data points, 24–237 months: Girls body mass index-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, birth to 33 months: Boys weight-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, birth to 33 months: Boys weight-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, birth to 33 months: Girls weight-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, birth to 33 months: Girls weight-for-age 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 vii 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 viii Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, birth to 33 months: Boys length-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, birth to 33 months: Boys length-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, birth to 33 months: Girls length-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, birth to 33 months: Girls length-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 46–103 cm: Boys weight- for-length Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 46–103 cm: Boys weight- for-length Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 46–103 cm: Girls weight- for-length Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 46–103 cm: Girls weight- for-length Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, birth to 33 months: Boys head circumference-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, birth to 33 months: Boys head circumference-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, birth to 33 months: Girls head circumference-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, birth to 33 months: Girls head circumference-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 84–122 cm: Boys weight- for-stature Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 84–122 cm: Boys weight- for-stature Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 84–122 cm: Girls weight- for-stature Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 84–122 cm: Girls weight- for-stature Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 27–237 months: Boys weight-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 27–237 months: Boys weight-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 27–237 months: Girls weight-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 27–237 months: Girls weight-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 27–237 months: Boys stature-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 27–237 months: Boys stature-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 27–237 months: Girls stature-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 95th percentile curves, 27–237 months: Girls stature-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 27–237 months: Boys body mass index-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 85th, 95th percentile curves, 27–237 months: Boys body mass index-for-age Percent of empirical data below smoothed 3rd, 10th, 50th, 90th, 97th percentile curves, 27–237 months: Girls body mass index-for-age Percent of empirical data below smoothed 5th, 25th, 50th, 75th, 85th, 95th percentile curves, 27–237 months: Girls body mass index-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, birth to 36 months: Boys weight-for-age 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 96 97 98 99 100 101 102 103 104 105 106 107 108 Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, birth to 36 months: Girls weight-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, birth to 36 months: Boys recumbent length-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, birth to 36 months: Girls recumbent length-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 49–94 cm: Boys weight-for-length Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 49–94 cm: Girls weight-for-length Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, birth to 36 months: Boys head circumference-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, birth to 36 months: Girls head circumference-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 91–120 cm: Boys weight-for-stature Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 91–120 cm: Girls weight-for-stature Comparison of revised CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 24–213 months: Boys weight-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 24–213 months: Girls weight-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 24–213 months: Boys stature-for-age Comparison of CDC 2000 smoothed 3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th percentiles with NCHS 1977 smoothed 5th, 10th, 25th, 50th, 75th, 90th, 95th percentile curves, 24–213 months: Girls stature-for-age 114 115 116 117 118 119 120 121 122 123 124 125 126 Text Tables A B C D Charts included in the 1977 NCHS Growth Charts and the 2000 CDC Growth Charts Source of data for each growth chart Primary and supplemental data sources Summary of curve smoothing procedures 2 3 4 6 Detailed Tables 1 2 3 4 5 6 7 8 9 10 11 12 Unweighted sample sizes for weight-for-age chart by sex, age, and data source: Births to 36 months Unweighted sample sizes for recumbent length-for-age chart by sex, age, and data source: Birth to 36 months Unweighted sample sizes for weight-for-recumbent length chart by sex, length interval, and data source: Birth to 36 months Unweighted sample sizes for head circumference-for-age chart by sex, age, and data source: Birth to 36 months Unweighted sample sizes for weight-for-stature chart by sex, stature interval, and data source: 77 to 121 cm Unweighted sample sizes for weight-for-age chart by sex, age, and data source: 2 to 20 years Unweighted sample sizes for stature-for-age chart by sex, age, and data source: 2 to 20 years Unweighted sample sizes for body mass index (BMI)-for-age chart by sex, age, and data source: 2 to 20 years Observed mean, standard deviation, and selected percentiles for weight (in kilograms) by sex and age: Birth to 36 months Observed mean, standard deviation, and selected percentiles for recumbent length (in centimeters) by sex and age: Birth to 36 months Observed mean, standard deviation, and selected percentiles for weight (in kilograms) by sex and recumbent length: Birth to 36 months Observed mean, standard deviation, and selected percentiles for head circumference (in centimeters) by sex and age: Birth to 36 months 127 128 129 130 131 132 134 136 138 139 140 141 ix 13 14 15 16 17 18 19 20 21 22 23 24 x Observed mean, standard deviation, and selected percentiles for weight (in kilograms) by sex and stature: 77 to 121 cm 142 Observed mean, standard deviation, and selected percentiles for weight (in kilograms) by sex and age: 2 to 20 years 143 Observed mean, standard deviation, and selected percentiles for stature (in centimeters) by sex and age: 2 to 20 years 145 Observed mean, standard deviation, and selected percentiles for body mass index (kilograms/meter2) by sex and age: 2 to 20 years 147 L, M, and S parameters and selected smoothed percentiles for weight (in kilograms) by sex and age: Birth to 36 months 149 L, M, and S parameters and selected smoothed percentiles for recumbent length (in centimeters) by sex and age: Birth to 36 months 151 L, M, and S parameters and selected smoothed percentiles for weight (in kilograms) by sex and recumbent length (in centimeters): Birth to 36 months 153 L, M, and S parameters and selected smoothed percentiles for head circumference (in centimeters) by sex and age: Birth to 36 months 156 L, M, and S parameters and selected smoothed percentiles for weight (in kilograms) by sex and stature (in centimeters): 77 to 121 cm 158 L, M, and S parameters and selected smoothed percentiles for weight (in kilograms) by sex and age: 2 to 20 years 160 L, M, and S parameters and selected smoothed percentiles for stature (in centimeters) by sex and age: 2 to 20 years 169 L, M, and S parameters and selected smoothed percentiles for body mass index (BMI, kilograms/meter2) by sex and age: 2 to 20 years 178 Series 11, No 246 [ Page 7 parametric form with estimated parameters specific for each selected major percentile The parameters of the linear regressions were estimated using the SAS procedure REG, and the parameters in the nonlinear regression were estimated using the SAS procedure NLIN (39) The fit of the models was evaluated using root mean square error (RMSE), R2, and CV (40) The Transformation Stage In order to estimate any percentile and allow calculation of standard deviation units and z-scores, a modified LMS statistical procedure was applied to the smoothed percentile curves The LMS method does not change the distribution of percentile curves in a growth chart; rather it provides a way to estimate percentiles in a continuous manner The distribution of some anthropometric data used in the growth charts are skewed To remove skewness, a power transformation can be used to stretch one tail of the distribution while the other tail is shrunk A Box-Cox transformation can make the distribution nearly normal (41) The assumption is that, after the appropriate power transformation, the data are closely approximated by a normal distribution (42) The transformation does not adjust for kurtosis, which is a less important contributor to nonnormality than skewness (43) In the LMS technique, three parameters are estimated: the median (M), the generalized coefficient of variation (S), and the power in the Box-Cox transformation (L) The L reflects the degree of skewness The LMS transformation equation is: X = M (1 + LSZ)1/LL ≠ 0 or X = M exp(SZ) L=0 where X is the physical measurement and Z is the z-score that corresponds to the percentile The key task of the transformation was to estimate parameters L, M, and S With estimates of L, M, and S, values of X are connected to the values of Z through the above equation The percentile is obtained from a normal distribution table where the z-score corresponds to the percentile of interest For example, a z-score of 0.2019 corresponds to the 58th percentile In the case of growth charts, with the L, M, and S parameters, it is possible to evaluate any single measure in a population as an exact z-score or percentile To generate age-specific estimates of L, M, and S, Cole (42,44) has recommended applying a penalized likelihood estimation procedure to the raw data In this approach smoothed curves of L, M, and S are generated first, and then smoothed percentile curves, or an individual standardized score, can be obtained from the values of L, M, and S In contrast to the original LMS procedure, a modified LMS estimation procedure was created and used to generate the 2000 CDC Growth Charts In the modified LMS approach, empirical percentile curves were initially smoothed and parametric models were generated, as described above Then, at each age or length/stature interval, a group of 9 equations (10 for BMI charts) was generated by specifying the LMS transformation equations for the previously smoothed major percentiles A simultaneous solution for the three parameters of L, M, and S from the group of specified equations was generated using the SAS procedure NLIN (39) By minimizing the sum of squared errors, the set of L, M, and S parameters was obtained as the best solution to a system of equations rather than as likelihood-based estimates from empirical data This approach is similar to the method used by Cole to estimate LMS parameters from published percentile curves (45–47) This modified LMS procedure produced final curves that are extremely close to the smoothed percentile curves obtained from the first stage of smoothing The net result is that the close fit of the smoothed curves from the first stage of smoothing to the empirical data is retained In addition, the modified LMS method allows z-scores to be obtained in a continuous manner The LMS values were calculated by solving equations that used the values for percentiles ranging from the 3rd to the 97th Percentiles less than the 3rd or greater than the 97th are beyond the range of the data from which the LMS parameters were calculated As in any statistical procedure, extrapolation beyond the range of the data should be done with caution The final set of percentile curves for the CDC growth charts presented in this report was produced using this modified LMS estimation procedure In the transformation stage, percentiles were developed at 1-month or 1-centimeter intervals in the infant and child charts Estimates of L, M, and S parameters in these intervals were calculated to provide the necessary tools for determining additional percentiles Generally, 1-month or 1-centimeter intervals will be adequate for estimation or evaluation To obtain percentiles at finer intervals, the L, M, and S values could be interpolated Detailed Procedures by Chart Weight-for-Age Combining infant and child/adolescent weight-for-age—After the infant weight-for-age and child/adolescent weight-for-age curves were smoothed using a 3-parameter linear model and LWR, the results were combined and refit from birth to age 20 years using a single regression model for each sex The smoothed weight-for-age curves for infants and for older children were combined to obtain a seamless transition between the curves Ultimately the combined weight-for-age curve was separated into infant and child/ adolescent curves to facilitate use in clinical settings In order to combine the infant and child/adolescent weight-for-age curves, weighted averages of overlapping empirical percentiles from infant and child charts at 2.25 years (24.0–29.9 months) and 2.75 years (30.0–35.9 months) were calculated using the combined infant and child/adolescent data The empirical percentiles were not identical at ages 24–36.9 months because VLBW infants (