Abstract: Background: Sitting height and leg length are the useful indicators for the linear growth evaluation of children and adolescents, but the growth reference standards of the two indicators have not been reported. Objective: To study and formulate the growth reference of sitting height and leg length of Chinese children and adolescents aged 0-18 years. Design: A cross-sectional survey. Methods: Stature and sitting height of 92,494 healthy urban children aged 0-18 years were measured in two national surveys in 2005 in China—The National Survey on the Physical Growth and Development of Children in the Nine Cities of China (NSPGDC) and The Chinese National Survey on Students' Constitution and Health (CNSSCH). Leg length was calculated by height minus sitting height. Growth reference standards of sitting height and leg length were constructed using the LMS method. Main outcome measures: Reference values of sitting height and leg length. Results: The percentile and the Z-scores reference values of sitting height and leg length for Chinese boys and girls aged 0-18 years were shown and their growth charts were drawn. Sitting height increased about 14 cm, 6 cm and 4 cm during the first, second and third year after birth, respectively. After that, the annual increment of sitting height is nearly 2-3 cm. Then the increments became slightly higher at 11-13 years for boys and 9-11 years for girls and gradually became smaller and smaller. Sitting height nearly stopped increasing at the age of 17 years for boys and 15 years for girls. Leg length increased respectively about 11-12 cm and 6.5 cm during the first and second year after birth, then the annual increment was 4-5 cm during 2-5 years, and leg length stopped increasing nearly at 15 years for boys and 13 years for girls. Conclusion: The growth reference standards of sitting height and leg length were formulated, which provide more data and reference for perfecting the growth evaluation system of children and adolescents in China.

Key words: Children and adolescents, Sitting height, Leg length, Growth reference, Growth chart