Context Malnutrition causes death and impaired health in millions of children. Existing interventions are effective under controlled conditions; however, little information is available on their effectiveness in large-scale programs. Objective To document the short-term nutritional impact of a large-scale, incentive-based development program in Mexico (Progress), which included a nutritional component. Design, Setting, and Participants A randomized effectiveness study of 347 communities randomly assigned to immediate incorporation to the program in 1998 (intervention group; n=205) or to incorporation in 1999 (crossover intervention group; n=142). A random sample of children in those communities was surveyed at baseline and at 1 and 2 years afterward. Participants were from low-income households in poor rural communities in 6 central Mexican states. Children (N=650) 12 months of age or younger (n=373 intervention group; n=277 crossover intervention group) were included in the analyses. Intervention Children and pregnant and lactating women in participating households received fortified nutrition supplements; and the families received nutrition education, health care, and cash transfers. Main Outcome Measures Two-year height increments and, anemia rates as measured by blood hemoglobin levels in participating children. Results Progresa was associated with better growth in height among the poorest and younger infants. Age- and length-adjusted height was greater by 1.1 cm (26.4 cm in the intervention group Vs 25.3 cm in the crossover intervention group) among infants younger than 6 months at baseline and who lived in the poorest households. After 1 year, mean hemoglobin values were higher in the intervention group (11.12 g/dL; 95% confidence interval [CI], 10.9-11.3 g/dL) than in the crossover intervention group (10.75 g/dL; 95% CI, 10.5-11.0 g/dL) who had not yet received the benefits of the intervention (P=.01). There were no differences in hemoglobin levels between the 2 groups at year 2 after both groups were receiving the intervention. The age-adjusted rate of anemia (hemoglobin level <11 g/dL) in 1999 was higher in the crossover intervention group than in the intervention group (54.9% vs 44.3%; P=.03), whereas in 2000 the difference was not significant (23.0% vs 25.8%, respectively; P=.40). Conclusion Progresa, a large-scale, incentive-based development program with a nutritional intervention, is associated with better growth and lower rates of anemia in low-income, rural infants and children in Mexico.
