Objective To describe some results of the epidemiological study “The impact of birth size on morbidity and on the physical, cognitive, affective and psychological development of Brazilian children” conducted in two cities with contrasting life conditions: Ribeirão Preto (RP), more developed, and São Luís (SL), less developed.

Methods Two cohorts, one with 2846 neonates born in 1994 in RP, and the other with 2542 neonates born in SL in 1997/98 were studied. During follow-up at school age, 1712 children aged 7–11 years were re-evaluated in RP (2004/05) and SL (2005/06). We used data from a general questionnaire, anthropometry, Raven Colored Progressive Matrices Test, Child Depression Inventory (CDI), a questionnaire about asthma, methacholine bronchial challenge test, and allergy skin tests. Since low birthweight infants were over-represented, appropriate sampling weights and stratification by birthweight were applied. Future studies will explore the effects of intrauterine life and childhood, testing etiologic hypotheses.

Results SL schoolchildren presented a higher percentage below the mean in the Raven test, 28.5%, compared to RP schoolchildren, 12.0% (p<0.001). The prevalence of childhood depression in SL, 21.7%, was 3.5 times higher than in RP, 6% (p<0.001). Excess weight was more prevalent in RP, 44%, than in SL, 22.1% (p<0.05). Asthma and bronchial hyperresponsiveness were more prevalent in RP, 12.2% and 38.4%, than in SL, 8.0 and 31.2% (p = 0.09 and p = 0.06).

Conclusions Depression and cognitive function deficits among schoolchildren were more prevalent in the less developed city, while atopy, asthma, bronchial hyperresponsiveness and excess weight predominated in the more developed city.