This paper summarizes the main findings of the Pelotas birth cohort studies of 1982 and 1993. There was a reduction in the number of births from 6,011 in 1982 to 5,304 in 1993, which was not evenly distributed, as there were around 1,000 fewer births in the poorest groups and 300 more in the high-income strata. Nutritional status of the mothers also varied in the decade, with an increase of 3.5 cm in mean height and 3.9 kg in mean weight at the beginning of pregnancy. Despite such improvements, the proportion of low birthweight increased from 9.0% in 1982 to 9.8% in 1993. Preterm births and intrauterine growth retardation also increased. There was a reduction in perinatal mortality from 32.2/1.000 births in 1982 to 22.1/1.000 births in 1993. Nutritional status at 12 months of age varied according to the indicator: there was a slight increase in low height for age in 1993, whereas a reduction was observed in the prevalence of low weight for age and weight for height. The infant mortality rate dropped from 36.4/1.000 live births in 1982 to 21.1/1.000 in 1993.