Objective: To describe the physical growth in weight and height of children less than two years of age cared for the Mexican Institute of Social Security (IMSS).
Material and method: A population-based National Survey, which was also regional representative, was carried out in Ordinary Regime (RO) and the IMSS-Oportunidades Program (IO). In two years (2000-2002) the study gathered data on 17,502 children from the RO and 9872 from IO. The measures of weight and length were made by nurses, according to WHO criteria. Growth is reported as weight and length for each month of age and gender, in tables and percentile curves derived from quintile regressions, using a third degree polynomial to smooth out the lines.
Results: The trends of the means of weight and height in the first two years of life in children cared by Instituto Mexicano del Seguro Social show a pattern similar to those described in healthy children in other populations. However, the values are lower than those obtained in developed countries.
Conclusions: Children's growth at two years of age at the Instituto Mexicano del Seguro Social shows a curve that is lower than that of the reference population recommended by the World Health Organization as an international standard.